Formula: provide compiler failure collections

`needs` allows formulae to specify dependencies on cross-compiler
dependencies, allowing multiple failures to be specified in a single
statement. For instance, `needs :cxx11` adds seven compiler failures.

Closes Homebrew/homebrew#22912.

2 files changed, 36 insertions, 0 deletions

diff --git a/Library/Homebrew/compilers.rb b/Library/Homebrew/compilers.rb
index bd3fde698..7473f12a7 100644
--- a/Library/Homebrew/compilers.rb
+++ b/Library/Homebrew/compilers.rb
@@ -28,6 +28,35 @@ class CompilerFailure
   attr_reader :compiler, :major_version
   attr_rw :cause, :version
 
+  MESSAGES = {
+    :cxx11 => 'This compiler does not support C++11'
+  }
+
+  COLLECTIONS = {
+    :cxx11 => [
+      [:gcc_4_0, proc { cause MESSAGES[:cxx11] }],
+      [:gcc, proc { cause MESSAGES[:cxx11] }],
+      [:clang, proc { build 425; cause MESSAGES[:cxx11] }],
+      [{:gcc => '4.3'}, proc { cause MESSAGES[:cxx11] }],
+      [{:gcc => '4.4'}, proc { cause MESSAGES[:cxx11] }],
+      [{:gcc => '4.5'}, proc { cause MESSAGES[:cxx11] }],
+      [{:gcc => '4.6'}, proc { cause MESSAGES[:cxx11] }]
+    ],
+    :openmp => [
+      [:clang, proc { cause 'clang does not support OpenMP' }]
+    ]
+  }
+
+  def self.for_standard standard
+    failures = COLLECTIONS.fetch(standard) do
+      raise ArgumentError, "\"#{standard}\" is not a recognized standard"
+    end
+
+    failures.map do |compiler, block|
+      CompilerFailure.new(compiler, &block)
+    end
+  end
+
   def initialize compiler, &block
     # Non-Apple compilers are in the format fails_with compiler => version
     if compiler.is_a? Hash
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 49271b76d..2fe485909 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -761,6 +761,13 @@ class Formula
       @cc_failures << CompilerFailure.new(compiler, &block)
     end
 
+    def needs *standards
+      @cc_failures ||= Set.new
+      standards.each do |standard|
+        @cc_failures.merge CompilerFailure.for_standard standard
+      end
+    end
+
     def require_universal_deps
       specs.each { |spec| spec.build.universal = true }
     end