1 files changed, 35 insertions, 0 deletions
diff --git a/Library/Homebrew/compat/requirements/emacs_requirement.rb b/Library/Homebrew/compat/requirements/emacs_requirement.rb
new file mode 100644
index 000000000..c8e2ec274
--- /dev/null
+++ b/Library/Homebrew/compat/requirements/emacs_requirement.rb
@@ -0,0 +1,35 @@
+class EmacsRequirement < Requirement
+  fatal true
+  default_formula "emacs"
+
+  def initialize(tags)
+    @version = tags.shift if /\d+\.*\d*/ =~ tags.first
+    super
+  end
+
+  satisfy build_env: false do
+    next false unless which "emacs"
+    next true unless @version
+    emacs_version = Utils.popen_read("emacs", "--batch", "--eval", "(princ emacs-version)")
+    Version.create(emacs_version) >= Version.create(@version)
+  end
+
+  env do
+    ENV.prepend_path "PATH", which("emacs").dirname
+    ENV["EMACS"] = "emacs"
+  end
+
+  def message
+    if @version
+      s = "Emacs #{@version} or later is required."
+    else
+      s = "Emacs is required."
+    end
+    s += super
+    s
+  end
+
+  def inspect
+    "#<#{self.class.name}: #{name.inspect} #{tags.inspect} version=#{@version.inspect}>"
+  end
+end