Strategy: Manually handle redirections

Library/Homebrew/livecheck/livecheck.rb

@@ -524,6 +524,7 @@ module Homebrew
 
         if debug
           puts "URL (strategy):   #{strategy_data[:url]}" if strategy_data[:url] != url
+          puts "URL (final):   #{strategy_data[:final_url]}" if strategy_data[:final_url]
           puts "Regex (strategy): #{strategy_data[:regex].inspect}" if strategy_data[:regex] != livecheck_regex
         end
 
@@ -564,6 +565,7 @@ module Homebrew
           }
           version_info[:meta][:url][:processed] = url if url != original_url
           version_info[:meta][:url][:strategy] = strategy_data[:url] if strategy_data[:url] != url
+          version_info[:meta][:url][:final] = strategy_data[:final_url] if strategy_data[:final_url]
           version_info[:meta][:strategies] = strategies.map { |s| livecheck_strategy_names[s] } if strategies.present?
           version_info[:meta][:regex] = regex.inspect if regex.present?
         end

Library/Homebrew/livecheck/strategy.rb

@@ -115,8 +115,27 @@ module Homebrew
         headers
       end
 
+      # Fetches the content at the URL and returns a hash containing the
+      # content and, if there are any redirections, the final URL.
+      #
+      # @param url [String] the URL of the content to check
+      # @return [Hash]
       def self.page_content(url)
-        URI.parse(url).open.read
+        original_url = url
+
+        # Manually handling `URI#open` redirections allows us to detect the
+        # resolved URL while also supporting HTTPS to HTTP redirections (which
+        # are normally forbidden by `OpenURI`).
+        begin
+          content = URI.parse(url).open(redirect: false, &:read)
+        rescue OpenURI::HTTPRedirect => e
+          url = e.uri.to_s
+          retry
+        end
+
+        data = { content: content }
+        data[:final_url] = url unless url == original_url
+        data
       end
     end
   end

Library/Homebrew/livecheck/strategy/page_match.rb

@@ -39,18 +39,17 @@ module Homebrew
           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.
+        # Uses the regex to match text in the content or, if a block is
+        # provided, passes the page content to the block to handle matching.
+        # With either approach, an array of unique matches is returned.
         #
-        # @param url [String] the URL of the content to check
+        # @param content [String] the page content to check
         # @param regex [Regexp] a regex used for matching versions in the
         #   content
         # @return [Array]
-        def self.page_matches(url, regex, &block)
-          page = Strategy.page_content(url)
-
+        def self.page_matches(content, regex, &block)
           if block
-            case (value = block.call(page))
+            case (value = block.call(content))
             when String
               return [value]
             when Array
@@ -60,7 +59,7 @@ module Homebrew
             end
           end
 
-          page.scan(regex).map do |match|
+          content.scan(regex).map do |match|
             case match
             when String
               match
@@ -79,8 +78,12 @@ module Homebrew
         def self.find_versions(url, regex, &block)
           match_data = { matches: {}, regex: regex, url: url }
 
-          page_matches(url, regex, &block).each do |match|
-            match_data[:matches][match] = Version.new(match)
+          match_data.merge!(Strategy.page_content(url))
+          content = match_data.delete(:content)
+          return match_data if content.blank?
+
+          page_matches(content, regex, &block).each do |match_text|
+            match_data[:matches][match_text] = Version.new(match_text)
           end
 
           match_data

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

@@ -6,11 +6,50 @@ 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" }
+  let(:url) { "https://brew.sh/blog/" }
+  let(:regex) { %r{href=.*?/homebrew[._-]v?(\d+(?:\.\d+)+)/?["' >]}i }
+
+  let(:page_content) {
+    <<~EOS
+      <!DOCTYPE html>
+      <html>
+        <head>
+          <meta charset="utf-8">
+          <title>Homebrew — Homebrew</title>
+        </head>
+        <body>
+          <ul class="posts">
+            <li><a href="/2020/12/01/homebrew-2.6.0/" title="2.6.0"><h2>2.6.0</h2><h3>01 Dec 2020</h3></a></li>
+            <li><a href="/2020/11/18/homebrew-tap-with-bottles-uploaded-to-github-releases/" title="Homebrew tap with bottles uploaded to GitHub Releases"><h2>Homebrew tap with bottles uploaded to GitHub Releases</h2><h3>18 Nov 2020</h3></a></li>
+            <li><a href="/2020/09/08/homebrew-2.5.0/" title="2.5.0"><h2>2.5.0</h2><h3>08 Sep 2020</h3></a></li>
+            <li><a href="/2020/06/11/homebrew-2.4.0/" title="2.4.0"><h2>2.4.0</h2><h3>11 Jun 2020</h3></a></li>
+            <li><a href="/2020/05/29/homebrew-2.3.0/" title="2.3.0"><h2>2.3.0</h2><h3>29 May 2020</h3></a></li>
+            <li><a href="/2019/11/27/homebrew-2.2.0/" title="2.2.0"><h2>2.2.0</h2><h3>27 Nov 2019</h3></a></li>
+            <li><a href="/2019/06/14/homebrew-maintainer-meeting/" title="Homebrew Maintainer Meeting"><h2>Homebrew Maintainer Meeting</h2><h3>14 Jun 2019</h3></a></li>
+            <li><a href="/2019/04/04/homebrew-2.1.0/" title="2.1.0"><h2>2.1.0</h2><h3>04 Apr 2019</h3></a></li>
+            <li><a href="/2019/02/02/homebrew-2.0.0/" title="2.0.0"><h2>2.0.0</h2><h3>02 Feb 2019</h3></a></li>
+            <li><a href="/2019/01/09/homebrew-1.9.0/" title="1.9.0"><h2>1.9.0</h2><h3>09 Jan 2019</h3></a></li>
+          </ul>
+        </body>
+      </html>
+    EOS
+  }
+  let(:page_content_matches) { ["2.6.0", "2.5.0", "2.4.0", "2.3.0", "2.2.0", "2.1.0", "2.0.0", "1.9.0"] }
 
   describe "::match?" do
     it "returns true for any URL" do
       expect(page_match.match?(url)).to be true
     end
   end
+
+  describe "::page_matches" do
+    it "finds matching text in page content using a regex" do
+      expect(page_match.page_matches(page_content, regex)).to eq(page_content_matches)
+    end
+
+    it "finds matching text in page content using a strategy block" do
+      expect(page_match.page_matches(page_content, regex) { |content| content.scan(regex).map(&:first).uniq })
+        .to eq(page_content_matches)
+    end
+  end
 end