fetch: add --all-platforms to fetch every cask variant

- Iterate the full OS/arch matrix plus each `language` for
  `--all-platforms`, downloading each distinct URL once. This covers
  per-macOS-version URL variants, not just a fixed set of corners.
- Collapse to a single combination for casks without `on_system`
  blocks, since they resolve identically on every platform.
- Tolerate `CaskInvalidError`/`CaskUnreadableError` for casks that omit
  some platforms (mirrors the `bump-cask-pr.rb` rescue pattern).
- Warn when a cask is loaded from the API, since OS/arch cannot be
  simulated without the source.

Signed-off-by: Patrick Linnane <patrick@linnane.io>

Author: p-linnane

Library/Homebrew/cli/args.rb

@@ -128,7 +128,10 @@ def only_formula_or_cask
       def os_arch_combinations
         skip_invalid_combinations = false
 
-        oses = case (os_sym = @table[:os]&.to_sym)
+        # `--all-platforms` is equivalent to `--os=all --arch=all`.
+        all_platforms = @table[:all_platforms?]
+
+        oses = case (os_sym = all_platforms ? :all : @table[:os]&.to_sym)
         when nil
           [SimulateSystem.current_os]
         when :all
@@ -139,7 +142,7 @@ def os_arch_combinations
           [os_sym]
         end
 
-        arches = case (arch_sym = @table[:arch]&.to_sym)
+        arches = case (arch_sym = all_platforms ? :all : @table[:arch]&.to_sym)
         when nil
           [SimulateSystem.current_arch]
         when :all

Library/Homebrew/cmd/fetch.rb

@@ -4,6 +4,7 @@
 require "abstract_command"
 require "formula"
 require "fetch"
+require "cask/config"
 require "cask/download"
 require "download_queue"
 
@@ -25,6 +26,9 @@ class FetchCmd < AbstractCommand
         flag   "--arch=",
                description: "Download for the given CPU architecture. " \
                             "(Pass `all` to download for all architectures.)"
+        switch "--all-platforms",
+               description: "Download each <cask> for every supported operating system, architecture and " \
+                            "language, fetching each distinct URL once."
         flag   "--bottle-tag=",
                description: "Download a bottle for given tag."
         switch "--HEAD",
@@ -65,6 +69,10 @@ class FetchCmd < AbstractCommand
         conflicts "--formula", "--cask"
         conflicts "--os", "--bottle-tag"
         conflicts "--arch", "--bottle-tag"
+        conflicts "--all-platforms", "--os"
+        conflicts "--all-platforms", "--arch"
+        conflicts "--all-platforms", "--bottle-tag"
+        conflicts "--all-platforms", "--formula"
 
         named_args [:formula, :cask], min: 1
       end
@@ -158,24 +166,59 @@ def run
             ref = cask.loaded_from_api? ? cask.full_name : cask.sourcefile_path
             odie "unexpected nil cask sourcefile_path" unless ref
 
-            os_arch_combinations.each do |os, arch|
-              SimulateSystem.with(os:, arch:) do
-                cask = Cask::CaskLoader.load(ref)
+            quarantine = args.quarantine?
+            quarantine = true if quarantine.nil?
+
+            if args.all_platforms? && cask.loaded_from_api?
+              opoo "Cask #{cask} was loaded from the API; cannot fetch all operating system and " \
+                   "architecture variants. Set `HOMEBREW_NO_INSTALL_FROM_API=1` to fetch them all."
+            end
+
+            # A cask without `on_system` blocks resolves identically on every
+            # OS/arch, so a single combination covers the whole matrix.
+            cask_combinations = if cask.on_system_blocks_exist?
+              os_arch_combinations
+            else
+              os_arch_combinations.first(1)
+            end
 
-                if cask.url.nil? || cask.sha256.nil?
-                  opoo "Cask #{cask} is not supported on os #{os} and arch #{arch}"
-                  next
+            enqueued_urls = Set.new
+
+            cask_combinations.each do |os, arch|
+              SimulateSystem.with(os:, arch:) do
+                loaded_cask = begin
+                  Cask::CaskLoader.load(ref)
+                rescue Cask::CaskInvalidError, Cask::CaskUnreadableError
+                  raise unless cask.on_system_blocks_exist?
                 end
+                next if loaded_cask.nil?
+
+                languages = (loaded_cask.languages if args.all_platforms?)
+                languages = [nil] if languages.blank?
+
+                languages.each do |language|
+                  localized_cask = loaded_cask
+                  if language
+                    localized_cask = Cask::CaskLoader.load(ref)
+                    localized_cask.config = localized_cask.config.merge(
+                      Cask::Config.new(explicit: { languages: [language] }),
+                    )
+                  end
 
-                quarantine = args.quarantine?
-                quarantine = true if quarantine.nil?
+                  if localized_cask.url.nil? || localized_cask.sha256.nil?
+                    opoo "Cask #{cask} is not supported on os #{os} and arch #{arch}"
+                    next
+                  end
 
-                download = Cask::Download.new(
-                  cask,
-                  quarantine:,
-                  require_sha: Homebrew::EnvConfig.cask_opts_require_sha?,
-                )
-                download_queue.enqueue(download)
+                  next unless enqueued_urls.add?(localized_cask.url.to_s)
+
+                  download = Cask::Download.new(
+                    localized_cask,
+                    quarantine:,
+                    require_sha: Homebrew::EnvConfig.cask_opts_require_sha?,
+                  )
+                  download_queue.enqueue(download)
+                end
               end
             end
           else

Library/Homebrew/sorbet/rbi/dsl/homebrew/cmd/fetch_cmd.rbi

@@ -1453,6 +1453,7 @@ _brew_fetch() {
     -*)
       __brewcomp "
       --HEAD
+      --all-platforms
       --arch
       --bottle-tag
       --build-bottle

completions/bash/brew

@@ -974,6 +974,7 @@ __fish_brew_complete_arg 'extract' -a '(__fish_brew_suggest_taps_installed)'
 
 __fish_brew_complete_cmd 'fetch' 'Download a bottle (if available) or source packages for formulae and binaries for casks'
 __fish_brew_complete_arg 'fetch' -l HEAD -d 'Fetch HEAD version instead of stable version'
+__fish_brew_complete_arg 'fetch' -l all-platforms -d 'Download each cask for every supported operating system, architecture and language, fetching each distinct URL once'
 __fish_brew_complete_arg 'fetch' -l arch -d 'Download for the given CPU architecture. (Pass `all` to download for all architectures.)'
 __fish_brew_complete_arg 'fetch' -l bottle-tag -d 'Download a bottle for given tag'
 __fish_brew_complete_arg 'fetch' -l build-bottle -d 'Download source packages (for eventual bottling) rather than a bottle'

completions/fish/brew.fish

@@ -1274,21 +1274,22 @@ _brew_extract() {
 _brew_fetch() {
   _arguments \
     '(--cask)--HEAD[Fetch HEAD version instead of stable version]' \
-    '(--bottle-tag)--arch[Download for the given CPU architecture. (Pass `all` to download for all architectures.)]' \
-    '(--build-from-source --build-bottle --force-bottle --cask --os --arch)--bottle-tag[Download a bottle for given tag]' \
+    '(--os --arch --bottle-tag --formula)--all-platforms[Download each cask for every supported operating system, architecture and language, fetching each distinct URL once]' \
+    '(--bottle-tag --all-platforms)--arch[Download for the given CPU architecture. (Pass `all` to download for all architectures.)]' \
+    '(--build-from-source --build-bottle --force-bottle --cask --os --arch --all-platforms)--bottle-tag[Download a bottle for given tag]' \
     '(--build-from-source --force-bottle --bottle-tag --cask)--build-bottle[Download source packages (for eventual bottling) rather than a bottle]' \
     '(--build-bottle --force-bottle --bottle-tag)--build-from-source[Download source packages rather than a bottle]' \
     '--debug[Display any debugging information]' \
     '(--cask)--deps[Also download dependencies for any listed formula]' \
     '--force[Remove a previously cached version and re-fetch]' \
     '(--build-from-source --build-bottle --bottle-tag --cask)--force-bottle[Download a bottle if it exists for the current or newest version of macOS, even if it would not be used during installation]' \
     '--help[Show this message]' \
-    '(--bottle-tag)--os[Download for the given operating system. (Pass `all` to download for all operating systems.)]' \
+    '(--bottle-tag --all-platforms)--os[Download for the given operating system. (Pass `all` to download for all operating systems.)]' \
     '--quiet[Make some output more quiet]' \
     '--retry[Retry if downloading fails or re-download if the checksum of a previously cached version no longer matches. Tries at most 5 times with exponential backoff]' \
     '--verbose[Do a verbose VCS checkout, if the URL represents a VCS. This is useful for seeing if an existing VCS cache has been updated]' \
     - formula \
-    '(--cask)--formula[Treat all named arguments as formulae]' \
+    '(--cask --all-platforms)--formula[Treat all named arguments as formulae]' \
     '*:formula:__brew_formulae' \
     - cask \
     '(--HEAD --deps -s --build-bottle --force-bottle --bottle-tag --formula)--cask[Treat all named arguments as casks]' \

completions/zsh/_brew

@@ -993,6 +993,11 @@ binaries for *`cask`*s. For files, also print SHA-256 checksums.
 : Download for the given CPU architecture. (Pass `all` to download for all
   architectures.)
 
+`--all-platforms`
+
+: Download each *`cask`* for every supported operating system, architecture and
+  language, fetching each distinct URL once.
+
 `--bottle-tag`
 
 : Download a bottle for given tag.

docs/Manpage.md

@@ -650,6 +650,9 @@ Download for the given operating system\. (Pass \fBall\fP to download for all op
 \fB\-\-arch\fP
 Download for the given CPU architecture\. (Pass \fBall\fP to download for all architectures\.)
 .TP
+\fB\-\-all\-platforms\fP
+Download each \fIcask\fP for every supported operating system, architecture and language, fetching each distinct URL once\.
+.TP
 \fB\-\-bottle\-tag\fP
 Download a bottle for given tag\.
 .TP