Add HOMEBREW_ARTIFACT_DOMAIN_NO_FALLBACK

This fits the use-case I've heard multiple times where people want to
rely exclusively on their artifact provider.

Co-authored-by: Carlo Cabrera <30379873+carlocab@users.noreply.github.com>

Library/Homebrew/cmd/vendor-install.sh

@@ -47,6 +47,11 @@ set_ruby_variables() {
     if [[ -n "${HOMEBREW_ARTIFACT_DOMAIN}" ]]
     then
       ruby_URLs+=("${HOMEBREW_ARTIFACT_DOMAIN}/v2/homebrew/portable-ruby/portable-ruby/blobs/sha256:${ruby_SHA}")
+      if [[ -n "${HOMEBREW_ARTIFACT_DOMAIN_NO_FALLBACK}" ]]
+      then
+        ruby_URL="${ruby_URLs[0]}"
+        return
+      fi
     fi
     if [[ -n "${HOMEBREW_BOTTLE_DOMAIN}" ]]
     then

Library/Homebrew/download_strategy.rb

@@ -405,6 +405,7 @@ class CurlDownloadStrategy < AbstractFileDownloadStrategy
 
       if (domain = Homebrew::EnvConfig.artifact_domain)
         url = url.sub(%r{^https?://#{GitHubPackages::URL_DOMAIN}/}o, "#{domain.chomp("/")}/")
+        urls = [] if Homebrew::EnvConfig.artifact_domain_no_fallback?
       end
 
       ohai "Downloading #{url}"

Library/Homebrew/env_config.rb

@@ -44,6 +44,12 @@ module Homebrew
                      "to instead be downloaded from " \
                      "`http://localhost:8080/v2/homebrew/core/gettext/manifests/0.21`",
       },
+      HOMEBREW_ARTIFACT_DOMAIN_NO_FALLBACK:      {
+        description: "If `HOMEBREW_ARTIFACT_DOMAIN` and `HOMEBREW_ARTIFACT_DOMAIN_NO_FALLBACK` are both set, " \
+                     "if the request to `HOMEBREW_ARTIFACT_DOMAIN` fails then it Homebrew will error rather than " \
+                     "trying any other/default URLs.",
+        boolean:     true,
+      },
       HOMEBREW_AUTO_UPDATE_SECS:                 {
         description:  "Run `brew update` once every `HOMEBREW_AUTO_UPDATE_SECS` seconds before some commands, " \
                       "e.g. `brew install`, `brew upgrade` and `brew tap`. Alternatively, " \

Library/Homebrew/resource.rb

@@ -237,8 +237,12 @@ class Resource < Downloadable
     # glibc-bootstrap
     if url.start_with?("https://github.com/Homebrew/glibc-bootstrap/releases/download")
       if (artifact_domain = Homebrew::EnvConfig.artifact_domain.presence)
-        extra_urls << url.sub("https://github.com", artifact_domain)
+        artifact_url = url.sub("https://github.com", artifact_domain)
+        return [artifact_url] if Homebrew::EnvConfig.artifact_domain_no_fallback?
+
+        extra_urls << artifact_url
       end
+
       if Homebrew::EnvConfig.bottle_domain != HOMEBREW_BOTTLE_DEFAULT_DOMAIN
         tag, filename = url.split("/").last(2)
         extra_urls << "#{Homebrew::EnvConfig.bottle_domain}/glibc-bootstrap/#{tag}/#{filename}"

Library/Homebrew/sorbet/rbi/dsl/homebrew/env_config.rbi

@@ -25,6 +25,9 @@ module Homebrew::EnvConfig
     sig { returns(T.nilable(::String)) }
     def artifact_domain; end
 
+    sig { returns(T::Boolean) }
+    def artifact_domain_no_fallback?; end
+
     sig { returns(T.nilable(::String)) }
     def auto_update_secs; end
 

docs/Manpage.md

@@ -3510,6 +3510,12 @@ command execution e.g. `$(cat file)`.
   downloaded from
   `http://localhost:8080/v2/homebrew/core/gettext/manifests/0.21`
 
+`HOMEBREW_ARTIFACT_DOMAIN_NO_FALLBACK`
+
+: If `HOMEBREW_ARTIFACT_DOMAIN` and `HOMEBREW_ARTIFACT_DOMAIN_NO_FALLBACK` are
+  both set, if the request to `HOMEBREW_ARTIFACT_DOMAIN` fails then it Homebrew
+  will error rather than trying any other/default URLs.
+
 `HOMEBREW_AUTO_UPDATE_SECS`
 
 : Run `brew update` once every `HOMEBREW_AUTO_UPDATE_SECS` seconds before some

manpages/brew.1

@@ -2244,6 +2244,9 @@ Linux only: Pass this value to a type name representing the compiler\[u2019]s \f
 \fBHOMEBREW_ARTIFACT_DOMAIN\fP
 Prefix all download URLs, including those for bottles, with this value\. For example, \fBHOMEBREW_ARTIFACT_DOMAIN=http://localhost:8080\fP will cause a formula with the URL \fBhttps://example\.com/foo\.tar\.gz\fP to instead download from \fBhttp://localhost:8080/https://example\.com/foo\.tar\.gz\fP\&\. Bottle URLs however, have their domain replaced with this prefix\. This results in e\.g\. \fBhttps://ghcr\.io/v2/homebrew/core/gettext/manifests/0\.21\fP to instead be downloaded from \fBhttp://localhost:8080/v2/homebrew/core/gettext/manifests/0\.21\fP
 .TP
+\fBHOMEBREW_ARTIFACT_DOMAIN_NO_FALLBACK\fP
+If \fBHOMEBREW_ARTIFACT_DOMAIN\fP and \fBHOMEBREW_ARTIFACT_DOMAIN_NO_FALLBACK\fP are both set, if the request to \fBHOMEBREW_ARTIFACT_DOMAIN\fP fails then it Homebrew will error rather than trying any other/default URLs\.
+.TP
 \fBHOMEBREW_AUTO_UPDATE_SECS\fP
 Run \fBbrew update\fP once every \fBHOMEBREW_AUTO_UPDATE_SECS\fP seconds before some commands, e\.g\. \fBbrew install\fP, \fBbrew upgrade\fP and \fBbrew tap\fP\&\. Alternatively, disable auto\-update entirely with \fBHOMEBREW_NO_AUTO_UPDATE\fP\&\.
 .RS