dev-cmd: avoid uploading identical bottles.

If the `rebuild`, `root_url`, `cellar` and checksums are all identical
between an old and new bottle block: we don't need a new bottle at
all. Handle this by deleting the relevant files with
`brew bottle --merge --write` and gracefully notifying the caller of
`brew pr-upload`.

This should avoid e.g.
39340a11ea
occurring in future.

Library/Homebrew/.rubocop.yml

@@ -18,6 +18,8 @@ Metrics/AbcSize:
 Metrics/BlockLength:
   Max: 100
   Exclude:
+    # TODO: extract more of the bottling logic
+    - "dev-cmd/bottle.rb"
     - "test/**/*"
 Metrics/BlockNesting:
   Max: 5
@@ -33,8 +35,10 @@ Metrics/PerceivedComplexity:
 Metrics/MethodLength:
   Max: 260
 Metrics/ModuleLength:
-  Max: 610
+  Max: 500
   Exclude:
+    # TODO: extract more of the bottling logic
+    - "dev-cmd/bottle.rb"
     - "test/**/*"
 
 Naming/PredicateName:

Library/Homebrew/dev-cmd/bottle.rb

@@ -640,8 +640,26 @@ module Homebrew
         break if all_bottle
       end
 
-      if args.write?
-        if all_bottle
+      unless args.write?
+        puts bottle_output(bottle)
+        next
+      end
+
+      path = HOMEBREW_REPOSITORY/bottle_hash["formula"]["path"]
+      formula = Formulary.factory(path)
+      old_bottle_spec = formula.bottle_specification
+
+      no_bottle_changes = if old_bottle_spec &&
+                             bottle_hash["formula"]["pkg_version"] == formula.pkg_version.to_s &&
+                             bottle.rebuild  != old_bottle_spec.rebuild &&
+                             bottle.root_url == old_bottle_spec.root_url
+        bottle.collector.keys.all? do |tag|
+          next false if bottle.collector[tag][:cellar] != old_bottle_spec.collector[tag][:cellar]
+
+          bottle.collector[tag][:checksum].hexdigest == old_bottle_spec.collector[tag][:checksum].hexdigest
+        end
+      end
+
       all_bottle_hash = nil
       bottle_hash["bottle"]["tags"].each do |tag, tag_hash|
         filename = Bottle::Filename.new(
@@ -651,7 +669,7 @@ module Homebrew
           bottle_hash["bottle"]["rebuild"],
         )
 
-            if all_bottle_hash.nil?
+        if all_bottle && all_bottle_hash.nil?
           all_bottle_tag_hash = tag_hash.dup
 
           all_filename = Bottle::Filename.new(
@@ -680,16 +698,17 @@ module Homebrew
           all_local_json_path.write(JSON.pretty_generate(all_bottle_hash))
         end
 
+        if all_bottle || no_bottle_changes
           puts "Removing #{filename} and #{filename.json}" if args.verbose?
           FileUtils.rm_f [filename.to_s, filename.json]
         end
       end
 
+      next if no_bottle_changes
+
       Homebrew.install_bundler_gems!
       require "utils/ast"
 
-        path = Pathname.new((HOMEBREW_REPOSITORY/bottle_hash["formula"]["path"]).to_s)
-        formula = Formulary.factory(path)
       formula_ast = Utils::AST::FormulaAST.new(path.read)
       checksums = old_checksums(formula, formula_ast, bottle_hash, args: args)
       update_or_add = checksums.nil? ? "add" : "update"
@@ -706,7 +725,8 @@ module Homebrew
       end
       path.atomic_write(formula_ast.process)
 
-        unless args.no_commit?
+      next if args.no_commit?
+
       Utils::Git.set_name_email!(committer: args.committer.blank?)
       Utils::Git.setup_gpg!
 
@@ -725,10 +745,6 @@ module Homebrew
                     "--", path
       end
     end
-      else
-        puts bottle_output(bottle)
-      end
-    end
   end
 
   def merge_bottle_spec(old_keys, old_bottle_spec, new_bottle_hash)

Library/Homebrew/dev-cmd/pr-upload.rb

@@ -84,9 +84,7 @@ module Homebrew
     end
   end
 
-  def json_files_and_bottles_hash(args)
-    json_files = Dir["*.bottle.json"]
-    odie "No bottle JSON files found in the current working directory" if json_files.blank?
+  def bottles_hash_from_json_files(json_files, args)
     puts "Reading JSON files: #{json_files.join(", ")}" if args.verbose?
 
     bottles_hash = json_files.reduce({}) do |hash, json_file|
@@ -99,13 +97,15 @@ module Homebrew
       end
     end
 
-    [json_files, bottles_hash]
+    bottles_hash
   end
 
   def pr_upload
     args = pr_upload_args.parse
 
-    json_files, bottles_hash = json_files_and_bottles_hash(args)
+    json_files = Dir["*.bottle.json"]
+    odie "No bottle JSON files found in the current working directory" if json_files.blank?
+    bottles_hash = bottles_hash_from_json_files(json_files, args)
 
     bottle_args = ["bottle", "--merge", "--write"]
     bottle_args << "--verbose" if args.verbose?
@@ -144,9 +144,15 @@ module Homebrew
 
     safe_system HOMEBREW_BREW_FILE, *bottle_args
 
+    json_files = Dir["*.bottle.json"]
+    if json_files.blank?
+      puts "No bottle JSON files after merge, no upload needed!"
+      return
+    end
+
     # Reload the JSON files (in case `brew bottle --merge` generated
     # `all: $SHA256` bottles)
-    _, bottles_hash = json_files_and_bottles_hash(args)
+    bottles_hash = bottles_hash_from_json_files(json_files, args)
 
     # Check the bottle commits did not break `brew audit`
     unless args.no_commit?