Merge pull request #8255 from nandahkrishna/migrate-livecheck-strategy

livecheck migration: add strategies

Library/Homebrew/livecheck/strategy.rb

@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    # The `Livecheck::Strategy` module contains the various strategies as well
+    # as some general-purpose methods for working with them. Within the context
+    # of the `brew livecheck` command, strategies are established procedures
+    # for finding new software versions at a given source.
+    #
+    # @api private
+    module Strategy
+      module_function
+
+      # Strategy priorities informally range from 1 to 10, where 10 is the
+      # highest priority. 5 is the default priority because it's roughly in
+      # the middle of this range. Strategies with a priority of 0 (or lower)
+      # are ignored.
+      DEFAULT_PRIORITY = 5
+      private_constant :DEFAULT_PRIORITY
+
+      # Creates and/or returns a `@strategies` `Hash` ,which maps a snake
+      # case strategy name symbol (e.g., `:page_match`) to the associated
+      # `Strategy`.
+      #
+      # At present, this should only be called after tap strategies have been
+      # loaded, otherwise livecheck won't be able to use them.
+      # @return [Hash]
+      def strategies
+        return @strategies if defined? @strategies
+
+        @strategies = {}
+        constants.sort.each do |strategy_symbol|
+          key = strategy_symbol.to_s.underscore.to_sym
+          strategy = const_get(strategy_symbol)
+          @strategies[key] = strategy
+        end
+        @strategies
+      end
+      private_class_method :strategies
+
+      # Returns the `Strategy` that corresponds to the provided `Symbol` (or
+      # `nil` if there is no matching `Strategy`).
+      # @param symbol [Symbol] the strategy name in snake case as a `Symbol`
+      #   (e.g., `:page_match`)
+      # @return [Strategy, nil]
+      def from_symbol(symbol)
+        strategies[symbol]
+      end
+
+      # Returns an array of strategies that apply to the provided URL.
+      # @param url [String] the URL to check for matching strategies
+      # @param regex_provided [Boolean] whether a regex is provided in a
+      #   `livecheck` block
+      # @return [Array]
+      def from_url(url, regex_provided = nil)
+        usable_strategies = strategies.values.select do |strategy|
+          # Ignore strategies with a priority of 0 or lower
+          next if strategy.const_defined?(:PRIORITY) && !strategy::PRIORITY.positive?
+
+          strategy.respond_to?(:match?) && strategy.match?(url)
+        end
+
+        usable_strategies << strategies[:page_match] if strategies.key?(:page_match) && regex_provided
+
+        # Sort usable strategies in descending order by priority, using the
+        # DEFAULT_PRIORITY when a strategy doesn't contain a PRIORITY constant
+        usable_strategies.sort_by do |strategy|
+          (strategy.const_defined?(:PRIORITY) ? -strategy::PRIORITY : -DEFAULT_PRIORITY)
+        end
+      end
+    end
+  end
+end
+
+require_relative "strategy/apache"
+require_relative "strategy/bitbucket"
+require_relative "strategy/git"
+require_relative "strategy/gnome"
+require_relative "strategy/gnu"
+require_relative "strategy/hackage"
+require_relative "strategy/launchpad"
+require_relative "strategy/npm"
+require_relative "strategy/page_match"
+require_relative "strategy/pypi"
+require_relative "strategy/sourceforge"
+require_relative "strategy/xorg"

Library/Homebrew/livecheck/strategy/apache.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Apache` strategy identifies versions of software at apache.org
+      # by checking directory listing pages.
+      #
+      # Apache URLs start with `https://www.apache.org/dyn/closer.lua?path=`.
+      #
+      # The `path` parameter takes one of the following formats:
+      # * `example/1.2.3/example-1.2.3.tar.gz`
+      # * `example/example-1.2.3/example-1.2.3.tar.gz`
+      # * `example/example-1.2.3-bin.tar.gz`
+      #
+      # When the `path` contains a version directory (e.g., `/1.2.3/`,
+      # `/example-1.2.3/`, etc.), the default regex matches numeric versions
+      # in directory names. Otherwise, the default regex matches numeric
+      # versions in filenames.
+      #
+      # @api public
+      class Apache
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = %r{www\.apache\.org/dyn/.+path=.+}i.freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to the `PageMatch#find_versions` method to identify versions in the
+        # content.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          %r{
+            path=
+            (?<path>.+?)/ # Path to directory of files or version directories
+            (?<prefix>[^/]*?) # Any text in filename or directory before version
+            v?\d+(?:\.\d+)+ # The numeric version
+            (?<suffix>/|[^/]*) # Any text in filename or directory after version
+          }ix =~ url
+
+          # Use `\.t` instead of specific tarball extensions (e.g., .tar.gz)
+          suffix.sub!(/\.t(?:ar\..+|[a-z0-9]+)$/i, "\.t")
+
+          # Example URL: `https://archive.apache.org/dist/example/`
+          page_url = "https://archive.apache.org/dist/#{path}/"
+
+          # Example directory regex: `%r{href=["']?v?(\d+(?:\.\d+)+)/}i`
+          # Example file regexes:
+          # * `/href=["']?example-v?(\d+(?:\.\d+)+)\.t/i`
+          # * `/href=["']?example-v?(\d+(?:\.\d+)+)-bin\.zip/i`
+          regex ||= /href=["']?#{Regexp.escape(prefix)}v?(\d+(?:\.\d+)+)#{Regexp.escape(suffix)}/i
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/bitbucket.rb

@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Bitbucket` strategy identifies versions of software at
+      # bitbucket.org by checking a repository's available downloads.
+      #
+      # Bitbucket URLs generally take one of the following formats:
+      # * `https://bitbucket.org/example/example/get/1.2.3.tar.gz`
+      # * `https://bitbucket.org/example/example/downloads/example-1.2.3.tar.gz`
+      #
+      # The `/get/` archive files are simply automated snapshots of the files
+      # for a given tag. The `/downloads/` archive files are files that have
+      # been uploaded instead.
+      #
+      # It's also possible for an archive to come from a repository's wiki,
+      # like:
+      # `https://bitbucket.org/example/example/wiki/downloads/example-1.2.3.zip`.
+      # This scenario is handled by this strategy as well and the `path` in
+      # this example would be `example/example/wiki` (instead of
+      # `example/example` with the previous URLs).
+      #
+      # The default regex identifies versions in archive files found in `href`
+      # attributes.
+      #
+      # @api public
+      class Bitbucket
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = %r{bitbucket\.org(/[^/]+){4}\.\w+}i.freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to the `PageMatch#find_versions` method to identify versions in the
+        # content.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          %r{
+            bitbucket\.org/
+            (?<path>.+?)/ # The path leading up to the get or downloads part
+            (?<dl_type>get|downloads)/ # An indicator of the file download type
+            (?<prefix>(?:[^/]+?[_-])?) # Filename text before the version
+            v?\d+(?:\.\d+)+ # The numeric version
+            (?<suffix>[^/]+) # Filename text after the version
+          }ix =~ url
+
+          # Use `\.t` instead of specific tarball extensions (e.g., .tar.gz)
+          suffix.sub!(/\.t(?:ar\..+|[a-z0-9]+)$/i, "\.t")
+
+          # `/get/` archives are Git tag snapshots, so we need to check that tab
+          # instead of the main `/downloads/` page
+          page_url = if dl_type == "get"
+            "https://bitbucket.org/#{path}/downloads/?tab=tags"
+          else
+            "https://bitbucket.org/#{path}/downloads/"
+          end
+
+          # Example regexes:
+          # * `/href=.*?v?(\d+(?:\.\d+)+)\.t/i`
+          # * `/href=.*?example-v?(\d+(?:\.\d+)+)\.t/i`
+          regex ||= /href=.*?#{Regexp.escape(prefix)}v?(\d+(?:\.\d+)+)#{Regexp.escape(suffix)}/i
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/git.rb

@@ -0,0 +1,107 @@
+# frozen_string_literal: true
+
+require "open3"
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Git` strategy identifies versions of software in a Git repository
+      # by checking the tags using `git ls-remote --tags`.
+      #
+      # Livecheck has historically prioritized the `Git` strategy over others
+      # and this behavior was continued when the priority setup was created.
+      # This is partly related to livecheck checking formula URLs in order of
+      # `head`, `stable`, and then `homepage`. The higher priority here may
+      # be removed (or altered) in the future if we reevaluate this particular
+      # behavior.
+      #
+      # This strategy does not have a default regex. Instead, it simply removes
+      # any non-digit text from the start of tags and parses the rest as a
+      # `Version`. This works for some simple situations but even one unusual
+      # tag can cause a bad result. It's better to provide a regex in a
+      # `livecheck` block, so `livecheck` only matches what we really want.
+      #
+      # @api public
+      class Git
+        # The priority of the strategy on an informal scale of 1 to 10 (from
+        # lowest to highest).
+        PRIORITY = 8
+
+        # Fetches a remote Git repository's tags using `git ls-remote --tags`
+        # and parses the command's output. If a regex is provided, it will be
+        # used to filter out any tags that don't match it.
+        # @param url [String] the URL of the Git repository to check
+        # @param regex [Regexp] the regex to use for filtering tags
+        # @return [Hash]
+        def self.tag_info(url, regex = nil)
+          # Open3#capture3 is used here because we need to capture stderr
+          # output and handle it in an appropriate manner. Alternatives like
+          # SystemCommand always print errors (as well as debug output) and
+          # don't meet the same goals.
+          stdout_str, stderr_str, _status = Open3.capture3(
+            { "GIT_TERMINAL_PROMPT" => "0" }, "git", "ls-remote", "--tags", url
+          )
+
+          tags_data = { tags: [] }
+          tags_data[:messages] = stderr_str.split("\n") if stderr_str.present?
+          return tags_data if stdout_str.blank?
+
+          # Isolate tag strings by removing leading/trailing text
+          stdout_str.gsub!(%r{^.*\trefs/tags/}, "")
+          stdout_str.gsub!("^{}", "")
+
+          tags = stdout_str.split("\n").uniq.sort
+          tags.select! { |t| t =~ regex } if regex
+          tags_data[:tags] = tags
+
+          tags_data
+        end
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          (DownloadStrategyDetector.detect(url) <= GitDownloadStrategy) == true
+        end
+
+        # Checks the Git tags for new versions. When a regex isn't provided,
+        # the `Git` strategy simply removes non-digits from the start of tag
+        # strings and parses the remaining text as a `Version`.
+        # @param url [String] the URL of the Git repository to check
+        # @param regex [Regexp] the regex to use for matching versions
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          match_data = { matches: {}, regex: regex, url: url }
+
+          tags_data = tag_info(url, regex)
+
+          if tags_data.key?(:messages)
+            match_data[:messages] = tags_data[:messages]
+            return match_data if tags_data[:tags].blank?
+          end
+
+          tags_only_debian = tags_data[:tags].all? { |tag| tag.start_with?("debian/") }
+
+          tags_data[:tags].each do |tag|
+            # Skip tag if it has a 'debian/' prefix and upstream does not do
+            # only 'debian/' prefixed tags
+            next if tag =~ %r{^debian/} && !tags_only_debian
+
+            captures = regex.is_a?(Regexp) ? tag.scan(regex) : []
+            tag_cleaned = if captures[0].is_a?(Array)
+              captures[0][0] # Use the first capture group (the version)
+            else
+              tag[/\D*(.*)/, 1] # Remove non-digits from the start of the tag
+            end
+
+            match_data[:matches][tag] = Version.new(tag_cleaned)
+          rescue TypeError
+            nil
+          end
+
+          match_data
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/gnome.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Gnome` strategy identifies versions of software at gnome.org by
+      # checking the available downloads found in a project's `cache.json`
+      # file.
+      #
+      # GNOME URLs generally follow a format like:
+      # `https://download.gnome.org/sources/example/1.2/example-1.2.3.tar.xz`.
+      #
+      # The default regex restricts matching to filenames containing a version
+      # with an even-numbered minor below 90, as these are stable releases.
+      #
+      # @api public
+      class Gnome
+        NICE_NAME = "GNOME"
+
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = /download\.gnome\.org/i.freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to the `PageMatch#find_versions` method to identify versions in the
+        # content.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          %r{/sources/(?<package_name>.*?)/}i =~ url
+
+          page_url = "https://download.gnome.org/sources/#{package_name}/cache.json"
+
+          # GNOME archive files seem to use a standard filename format, so we
+          # count on the delimiter between the package name and numeric version
+          # being a hyphen and the file being a tarball.
+          #
+          # The `([0-8]\d*?)?[02468]` part of the regex is intended to restrict
+          # matching to versions with an even-numbered minor, as these are
+          # stable releases. This also excludes x.90+ versions, which are
+          # development versions. See: https://www.gnome.org/gnome-3/source/
+          #
+          # Example regex: `/example-(\d+\.([0-8]\d*?)?[02468](?:\.\d+)*?)\.t/i`
+          regex ||= /#{Regexp.escape(package_name)}-(\d+\.([0-8]\d*?)?[02468](?:\.\d+)*?)\.t/i
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/gnu.rb

@@ -0,0 +1,95 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Gnu` strategy identifies versions of software at gnu.org by
+      # checking directory listing pages.
+      #
+      # GNU URLs use a variety of formats:
+      #
+      # Archive file URLs:
+      # * `https://ftp.gnu.org/gnu/example/example-1.2.3.tar.gz`
+      # * `https://ftp.gnu.org/gnu/example/1.2.3/example-1.2.3.tar.gz`
+      #
+      # Homepage URLs:
+      # * `https://www.gnu.org/software/example/`
+      # * `https://example.gnu.org`
+      #
+      # There are other URL formats that this strategy currently doesn't
+      # support:
+      # * `https://ftp.gnu.org/non-gnu/example/source/feature/1.2.3/example-1.2.3.tar.gz`
+      # * `https://savannah.nongnu.org/download/example/example-1.2.3.tar.gz`
+      # * `https://download.savannah.gnu.org/releases/example/example-1.2.3.tar.gz`
+      # * `https://download.savannah.nongnu.org/releases/example/example-1.2.3.tar.gz`
+      #
+      # The default regex identifies versions in archive files found in `href`
+      # attributes.
+      #
+      # @api public
+      class Gnu
+        NICE_NAME = "GNU"
+
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = %r{
+          //.+?\.gnu\.org$|
+          gnu\.org/(?:gnu|software)/
+        }ix.freeze
+
+        # The `Regexp` used to parse the project name from the provided URL.
+        # The strategy uses this information to create the URL to check and
+        # the default regex.
+        PROJECT_NAME_REGEXES = [
+          %r{/(?:gnu|software)/(?<project_name>.+?)/}i,
+          %r{//(?<project_name>.+?)\.gnu\.org(?:/)?$}i,
+        ].freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url) && !url.include?("savannah.")
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to the `PageMatch#find_versions` method to identify versions in the
+        # content.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          project_names = PROJECT_NAME_REGEXES.map do |project_name_regex|
+            m = url.match(project_name_regex)
+            m["project_name"] if m
+          end.compact
+          return { matches: {}, regex: regex, url: url } if project_names.blank?
+
+          if project_names.length > 1
+            odebug <<~EOS
+
+              Multiple project names found: #{match_list}
+
+            EOS
+          end
+
+          project_name = project_names.first
+
+          # The directory listing page for the project's files
+          page_url = "http://ftp.gnu.org/gnu/#{project_name}/?C=M&O=D"
+
+          # The default regex consists of the following parts:
+          # * `href=.*?`: restricts matching to URLs in `href` attributes
+          # * The project name
+          # * `[._-]`: the generic delimiter between project name and version
+          # * `v?(\d+(?:\.\d+)*)`: the numeric version
+          # * `(?:\.[a-z]+|/)`: the file extension (a trailing delimiter)
+          #
+          # Example regex: `%r{href=.*?example[._-]v?(\d+(?:\.\d+)*)(?:\.[a-z]+|/)}i`
+          regex ||= %r{href=.*?#{project_name}[._-]v?(\d+(?:\.\d+)*)(?:\.[a-z]+|/)}i
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/hackage.rb

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Hackage` strategy identifies versions of software at
+      # hackage.haskell.org by checking directory listing pages.
+      #
+      # Hackage URLs take one of the following formats:
+      # * `https://hackage.haskell.org/package/example-1.2.3/example-1.2.3.tar.gz`
+      # * `https://downloads.haskell.org/~ghc/8.10.1/ghc-8.10.1-src.tar.xz`
+      #
+      # The default regex checks for the latest version an `h3` heading element
+      # with a format like `<h3>example-1.2.3/</h3>`.
+      #
+      # @api public
+      class Hackage
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = /(?:downloads|hackage)\.haskell\.org/i.freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to the `PageMatch#find_versions` method to identify versions in the
+        # content.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          /^(?<package_name>.+?)-\d+/i =~ File.basename(url)
+
+          # A page containing a directory listing of the latest source tarball
+          page_url = "https://hackage.haskell.org/package/#{package_name}/src"
+
+          # Example regex: `%r{<h3>example-(.*?)/?</h3>}i`
+          regex ||= %r{<h3>#{Regexp.escape(package_name)}-(.*?)/?</h3>}i
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/launchpad.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Launchpad` strategy identifies versions of software at
+      # launchpad.net by checking the main page for a project.
+      #
+      # Launchpad URLs take a variety of formats but all the current formats
+      # contain the project name as the first part of the URL path:
+      # * `https://launchpad.net/example/1.2/1.2.3/+download/example-1.2.3.tar.gz`
+      # * `https://launchpad.net/example/trunk/1.2.3/+download/example-1.2.3.tar.gz`
+      # * `https://code.launchpad.net/example/1.2/1.2.3/+download/example-1.2.3.tar.gz`
+      #
+      # The default regex identifies the latest version within an HTML element
+      # found on the main page for a project:
+      # ```html
+      # <div class="version">
+      #   Latest version is 1.2.3
+      # </div>
+      # ```
+      #
+      # @api public
+      class Launchpad
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = /launchpad\.net/i.freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to the `PageMatch#find_versions` method to identify versions in the
+        # content.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          %r{launchpad\.net/(?<project_name>[^/]+)}i =~ url
+
+          # The main page for the project on Launchpad
+          page_url = "https://launchpad.net/#{project_name}"
+
+          # The default regex is the same for all URLs using this strategy
+          regex ||= %r{class="[^"]*version[^"]*"[^>]*>\s*Latest version is (.+)\s*</}
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/npm.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `npm` strategy identifies versions of software at
+      # registry.npmjs.org by checking the listed versions for a package.
+      #
+      # npm URLs take one of the following formats:
+      # * `https://registry.npmjs.org/example/-/example-1.2.3.tgz`
+      # * `https://registry.npmjs.org/@example/example/-/example-1.2.3.tgz`
+      #
+      # The default regex matches URLs in the `href` attributes of version tags
+      # on the "Versions" tab of the package page.
+      #
+      # @api public
+      class Npm
+        NICE_NAME = "npm"
+
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = /registry\.npmjs\.org/i.freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to the `PageMatch#find_versions` method to identify versions in the
+        # content.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          %r{registry\.npmjs\.org/(?<package_name>.+)/-/}i =~ url
+
+          page_url = "https://www.npmjs.com/package/#{package_name}?activeTab=versions"
+
+          # Example regexes:
+          # * `%r{href=.*?/package/example/v/(\d+(?:\.\d+)+)"}i`
+          # * `%r{href=.*?/package/@example/example/v/(\d+(?:\.\d+)+)"}i`
+          regex ||= %r{href=.*?/package/#{Regexp.escape(package_name)}/v/(\d+(?:\.\d+)+)"}i
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/page_match.rb

@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+require "open-uri"
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `PageMatch` strategy fetches content at a URL and scans it for
+      # matching text using the provided regex.
+      #
+      # This strategy can be used in a `livecheck` block when no specific
+      # strategies apply to a given URL. Though `PageMatch` will technically
+      # match any HTTP URL, the strategy also requires a regex to function.
+      #
+      # The `PageMatch#find_versions` method is also used within other
+      # strategies, to handle the process of identifying version text in
+      # content.
+      #
+      # @api public
+      class PageMatch
+        NICE_NAME = "Page match"
+
+        # A priority of zero causes livecheck to skip the strategy. We do this
+        # for `PageMatch` so we can selectively apply the strategy only when a
+        # regex is provided in a `livecheck` block.
+        PRIORITY = 0
+
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = %r{^https?://}i.freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        #
+        # PageMatch will technically match any HTTP URL but it's only usable
+        # when the formula has a `livecheck` block containing a regex.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Fetches the content at the URL, uses the regex to match text, and
+        # returns an array of unique matches.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in the
+        #   content
+        # @return [Array]
+        def self.page_matches(url, regex)
+          page = URI.open(url).read
+          matches = page.scan(regex)
+          matches.map(&:first).uniq
+        end
+
+        # Checks the content at the URL for new versions, using the provided
+        # regex for matching.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex)
+          match_data = { matches: {}, regex: regex, url: url }
+
+          page_matches(url, regex).each do |match|
+            match_data[:matches][match] = Version.new(match)
+          end
+
+          match_data
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/pypi.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Pypi` strategy identifies versions of software at pypi.org by
+      # checking project pages for archive files.
+      #
+      # PyPI URLs have a standard format but the hexadecimal text between
+      # `/packages/` and the filename varies:
+      # * `https://files.pythonhosted.org/packages/<hex>/<hex>/<long_hex>/example-1.2.3.tar.gz`
+      #
+      # As such, the default regex only targets the filename at the end of the
+      # URL.
+      #
+      # @api public
+      class Pypi
+        NICE_NAME = "PyPI"
+
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = /files\.pythonhosted\.org/i.freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to the `PageMatch#find_versions` method to identify versions in the
+        # content.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          /
+            (?<package_name>.+)- # The package name followed by a hyphen
+            .*? # The version string
+            (?<suffix>\.tar\.[a-z0-9]+|\.[a-z0-9]+)$ # Filename extension
+          /ix =~ File.basename(url)
+
+          # Use `\.t` instead of specific tarball extensions (e.g., .tar.gz)
+          suffix.sub!(/\.t(?:ar\..+|[a-z0-9]+)$/i, "\.t")
+
+          # It's not technically necessary to have the `#files` fragment at the
+          # end of the URL but it makes the debug output a bit more useful.
+          page_url = "https://pypi.org/project/#{package_name.gsub(/%20|_/, "-")}#files"
+
+          # Example regex: `%r{href=.*?/packages.*?/example[._-]v?(\d+(?:\.\d+)*).t}i`.
+          regex ||=
+            %r{href=.*?/packages.*?/#{Regexp.escape(package_name)}[._-]v?(\d+(?:\.\d+)*)#{Regexp.escape(suffix)}}i
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/sourceforge.rb

@@ -0,0 +1,71 @@
+# frozen_string_literal: true
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Sourceforge` strategy identifies versions of software at
+      # sourceforge.net by checking a project's RSS feed.
+      #
+      # SourceForge URLs take a few different formats:
+      # * https://downloads.sourceforge.net/project/example/example-1.2.3.tar.gz
+      # * https://svn.code.sf.net/p/example/code/trunk
+      # * :pserver:anonymous:@example.cvs.sourceforge.net:/cvsroot/example
+      #
+      # The RSS feed for a project contains the most recent release archives
+      # and this is fine for most projects but this approach has some
+      # shortcomings. Some project releases involve so many files that the one
+      # we're interested in isn't present in the feed content. Some projects
+      # contain additional software and the archive we're interested in is
+      # pushed out of the feed (especially if it hasn't been updated recently).
+      #
+      # Usually we address this situation by adding a `livecheck` block to
+      # the formula that checks the page for the relevant directory in the
+      # project instead. In this situation, it's necessary to use
+      # `strategy :page_match` to prevent the `Sourceforge` stratgy from
+      # being used.
+      #
+      # The default regex matches within `url` attributes in the RSS feed
+      # and identifies versions within directory names or filenames.
+      #
+      # @api public
+      class Sourceforge
+        NICE_NAME = "SourceForge"
+
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = /(?:sourceforge|sf)\.net/i.freeze
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Generates a URL and regex (if one isn't provided) and passes them
+        # to the `PageMatch#find_versions` method to identify versions in the
+        # content.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex = nil)
+          if url.include?("/project")
+            %r{/projects?/(?<project_name>[^/]+)/}i =~ url
+          elsif url.include?(".net/p/")
+            %r{\.net/p/(?<project_name>[^/]+)/}i =~ url
+          else
+            %r{\.net(?::/cvsroot)?/(?<project_name>[^/]+)}i =~ url
+          end
+
+          page_url = "https://sourceforge.net/projects/#{project_name}/rss"
+
+          # It may be possible to improve the default regex but there's quite a
+          # bit of variation between projects and it can be challenging to
+          # create something that works for most URLs.
+          regex ||= %r{url=.*?/#{Regexp.escape(project_name)}/files/.*?[-_/](\d+(?:[-.]\d+)+)[-_/%.]}i
+
+          Homebrew::Livecheck::Strategy::PageMatch.find_versions(page_url, regex)
+        end
+      end
+    end
+  end
+end

Library/Homebrew/livecheck/strategy/xorg.rb

@@ -0,0 +1,97 @@
+# frozen_string_literal: true
+
+require "open-uri"
+
+module Homebrew
+  module Livecheck
+    module Strategy
+      # The `Xorg` strategy identifies versions of software at x.org by
+      # checking directory listing pages.
+      #
+      # X.Org URLs take one of the following formats, among several others:
+      # * `https://www.x.org/archive/individual/app/example-1.2.3.tar.bz2`
+      # * `https://www.x.org/archive/individual/font/example-1.2.3.tar.bz2`
+      # * `https://www.x.org/archive/individual/lib/libexample-1.2.3.tar.bz2`
+      # * `https://ftp.x.org/archive/individual/lib/libexample-1.2.3.tar.bz2`
+      # * `https://www.x.org/pub/individual/doc/example-1.2.3.tar.gz`
+      #
+      # The notable differences between URLs are as follows:
+      # * `www.x.org` and `ftp.x.org` seem to be interchangeable (we prefer
+      #   `www.x.org`).
+      # * `/archive/` is the current top-level directory and `/pub/` will
+      #   redirect to the same URL using `/archive/` instead. [The strategy
+      #   handles this replacement to avoid the redirection.]
+      # * The `/individual/` directory contains a number of directories (e.g.,
+      #   app, data, doc, driver, font, lib, etc.) which contain a number of
+      #   different archive files.
+      #
+      # Since this strategy ends up checking the same directory listing pages
+      # for multiple formulae, we've included a simple method of page caching.
+      # This prevents livecheck from fetching the same page more than once and
+      # also dramatically speeds up these checks. Eventually we hope to
+      # implement a more sophisticated page cache that all strategies using
+      # `PageMatch` can use (and we can simplify this strategy accordingly).
+      #
+      # The default regex identifies versions in archive files found in `href`
+      # attributes.
+      #
+      # @api public
+      class Xorg
+        NICE_NAME = "X.Org"
+
+        # The `Regexp` used to determine if the strategy applies to the URL.
+        URL_MATCH_REGEX = %r{
+          [/.]x\.org.*?/individual/|
+          freedesktop\.org/(?:archive|dist|software)/
+        }ix.freeze
+
+        # Used to cache page content, so we don't fetch the same pages
+        # repeatedly.
+        @page_data = {}
+
+        # Whether the strategy can be applied to the provided URL.
+        # @param url [String] the URL to match against
+        # @return [Boolean]
+        def self.match?(url)
+          URL_MATCH_REGEX.match?(url)
+        end
+
+        # Generates a URL and regex (if one isn't provided) and checks the
+        # content at the URL for new versions (using the regex for matching).
+        #
+        # The behavior in this method for matching text in the content using a
+        # regex is copied and modified from the `PageMatch` strategy, so that
+        # we can add some simple page caching. If this behavior is expanded to
+        # apply to all strategies that use `PageMatch` to identify versions,
+        # then the `Xorg` strategy can be brought in line with the others.
+        # @param url [String] the URL of the content to check
+        # @param regex [Regexp] a regex used for matching versions in content
+        # @return [Hash]
+        def self.find_versions(url, regex)
+          file_name = File.basename(url)
+
+          /^(?<module_name>.+)-\d+/i =~ file_name
+
+          # /pub/ URLs redirect to the same URL with /archive/, so we replace
+          # it to avoid the redirection. Removing the filename from the end of
+          # the URL gives us the relevant directory listing page.
+          page_url = url.sub("x.org/pub/", "x.org/archive/").delete_suffix(file_name)
+
+          regex ||= /href=.*?#{Regexp.escape(module_name)}[._-]v?(\d+(?:\.\d+)+)\.t/i
+
+          match_data = { matches: {}, regex: regex, url: page_url }
+
+          # Cache responses to avoid unnecessary duplicate fetches
+          @page_data[page_url] = URI.open(page_url).read unless @page_data.key?(page_url)
+
+          matches = @page_data[page_url].scan(regex)
+          matches.map(&:first).uniq.each do |match|
+            match_data[:matches][match] = Version.new(match)
+          end
+
+          match_data
+        end
+      end
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/apache_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/apache"
+
+describe Homebrew::Livecheck::Strategy::Apache do
+  subject(:apache) { described_class }
+
+  let(:apache_url) { "https://www.apache.org/dyn/closer.lua?path=abc/1.2.3/def-1.2.3.tar.gz" }
+  let(:non_apache_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is an Apache URL" do
+      expect(apache.match?(apache_url)).to be true
+    end
+
+    it "returns false if the argument provided is not an Apache URL" do
+      expect(apache.match?(non_apache_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/bitbucket_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/bitbucket"
+
+describe Homebrew::Livecheck::Strategy::Bitbucket do
+  subject(:bitbucket) { described_class }
+
+  let(:bitbucket_url) { "https://bitbucket.org/abc/def/get/1.2.3.tar.gz" }
+  let(:non_bitbucket_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is a Bitbucket URL" do
+      expect(bitbucket.match?(bitbucket_url)).to be true
+    end
+
+    it "returns false if the argument provided is not a Bitbucket URL" do
+      expect(bitbucket.match?(non_bitbucket_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/git_spec.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/git"
+
+describe Homebrew::Livecheck::Strategy::Git do
+  subject(:git) { described_class }
+
+  let(:git_url) { "https://github.com/Homebrew/brew.git" }
+  let(:non_git_url) { "https://brew.sh/test" }
+
+  describe "::tag_info", :needs_network do
+    it "returns the Git tags for the provided remote URL that match the regex provided" do
+      expect(git.tag_info(git_url, /^v?(\d+(?:\.\d+))$/))
+        .not_to be_empty
+    end
+  end
+
+  describe "::match?" do
+    it "returns true if the argument provided is a Git repository" do
+      expect(git.match?(git_url)).to be true
+    end
+
+    it "returns false if the argument provided is not a Git repository" do
+      expect(git.match?(non_git_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/gnome_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/gnome"
+
+describe Homebrew::Livecheck::Strategy::Gnome do
+  subject(:gnome) { described_class }
+
+  let(:gnome_url) { "https://download.gnome.org/sources/abc/1.2/def-1.2.3.tar.xz" }
+  let(:non_gnome_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is a GNOME URL" do
+      expect(gnome.match?(gnome_url)).to be true
+    end
+
+    it "returns false if the argument provided is not a GNOME URL" do
+      expect(gnome.match?(non_gnome_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/gnu_spec.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/gnu"
+
+describe Homebrew::Livecheck::Strategy::Gnu do
+  subject(:gnu) { described_class }
+
+  let(:gnu_url) { "https://ftp.gnu.org/gnu/abc/def-1.2.3.tar.gz" }
+  let(:savannah_gnu_url) { "https://download.savannah.gnu.org/releases/abc/def-1.2.3.tar.gz" }
+  let(:non_gnu_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is a non-Savannah GNU URL" do
+      expect(gnu.match?(gnu_url)).to be true
+    end
+
+    it "returns false if the argument provided is a Savannah GNU URL" do
+      expect(gnu.match?(savannah_gnu_url)).to be false
+    end
+
+    it "returns false if the argument provided is not a GNU URL" do
+      expect(gnu.match?(non_gnu_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/hackage_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/hackage"
+
+describe Homebrew::Livecheck::Strategy::Hackage do
+  subject(:hackage) { described_class }
+
+  let(:hackage_url) { "https://hackage.haskell.org/package/abc-1.2.3/def-1.2.3.tar.gz" }
+  let(:non_hackage_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is a Hackage URL" do
+      expect(hackage.match?(hackage_url)).to be true
+    end
+
+    it "returns false if the argument provided is not a Hackage URL" do
+      expect(hackage.match?(non_hackage_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/launchpad_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/launchpad"
+
+describe Homebrew::Livecheck::Strategy::Launchpad do
+  subject(:launchpad) { described_class }
+
+  let(:launchpad_url) { "https://launchpad.net/abc/1.2/1.2.3/+download/def-1.2.3.tar.gz" }
+  let(:non_launchpad_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is a Launchpad URL" do
+      expect(launchpad.match?(launchpad_url)).to be true
+    end
+
+    it "returns false if the argument provided is not a Launchpad URL" do
+      expect(launchpad.match?(non_launchpad_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/npm_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/npm"
+
+describe Homebrew::Livecheck::Strategy::Npm do
+  subject(:npm) { described_class }
+
+  let(:npm_url) { "https://registry.npmjs.org/abc/-/def-1.2.3.tgz" }
+  let(:non_npm_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is an npm URL" do
+      expect(npm.match?(npm_url)).to be true
+    end
+
+    it "returns false if the argument provided is not an npm URL" do
+      expect(npm.match?(non_npm_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/page_match_spec.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/page_match"
+
+describe Homebrew::Livecheck::Strategy::PageMatch do
+  subject(:page_match) { described_class }
+
+  let(:url) { "http://api.github.com/Homebrew/brew/releases/latest" }
+
+  describe "::match?" do
+    it "returns true for any URL" do
+      expect(page_match.match?(url)).to be true
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/pypi_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/pypi"
+
+describe Homebrew::Livecheck::Strategy::Pypi do
+  subject(:pypi) { described_class }
+
+  let(:pypi_url) { "https://files.pythonhosted.org/packages/ab/cd/efg/hij-1.2.3.tar.gz" }
+  let(:non_pypi_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is a PyPI URL" do
+      expect(pypi.match?(pypi_url)).to be true
+    end
+
+    it "returns false if the argument provided is not a PyPI URL" do
+      expect(pypi.match?(non_pypi_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/sourceforge_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/sourceforge"
+
+describe Homebrew::Livecheck::Strategy::Sourceforge do
+  subject(:sourceforge) { described_class }
+
+  let(:sourceforge_url) { "https://downloads.sourceforge.net/project/abc/def-1.2.3.tar.gz" }
+  let(:non_sourceforge_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is a SourceForge URL" do
+      expect(sourceforge.match?(sourceforge_url)).to be true
+    end
+
+    it "returns false if the argument provided is not a SourceForge URL" do
+      expect(sourceforge.match?(non_sourceforge_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy/xorg_spec.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy/xorg"
+
+describe Homebrew::Livecheck::Strategy::Xorg do
+  subject(:xorg) { described_class }
+
+  let(:xorg_url) { "https://www.x.org/archive/individual/app/abc-1.2.3.tar.bz2" }
+  let(:non_xorg_url) { "https://brew.sh/test" }
+
+  describe "::match?" do
+    it "returns true if the argument provided is an X.Org URL" do
+      expect(xorg.match?(xorg_url)).to be true
+    end
+
+    it "returns false if the argument provided is not an X.Org URL" do
+      expect(xorg.match?(non_xorg_url)).to be false
+    end
+  end
+end

Library/Homebrew/test/livecheck/strategy_spec.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+require "livecheck/strategy"
+
+describe Homebrew::Livecheck::Strategy do
+  subject(:strategy) { described_class }
+
+  describe "::from_symbol" do
+    it "returns the Strategy module represented by the Symbol argument" do
+      expect(strategy.from_symbol(:page_match)).to eq(Homebrew::Livecheck::Strategy::PageMatch)
+    end
+  end
+
+  describe "::from_url" do
+    let(:url) { "https://sourceforge.net/projects/test" }
+
+    context "when no regex is provided" do
+      it "returns an array of usable strategies which doesn't include PageMatch" do
+        expect(strategy.from_url(url)).to eq([Homebrew::Livecheck::Strategy::Sourceforge])
+      end
+    end
+
+    context "when a regex is provided" do
+      it "returns an array of usable strategies including PageMatch, sorted in descending order by priority" do
+        expect(strategy.from_url(url, regex_provided: true))
+          .to eq(
+            [Homebrew::Livecheck::Strategy::Sourceforge, Homebrew::Livecheck::Strategy::PageMatch],
+          )
+      end
+    end
+  end
+end