Merge pull request #13690 from carlocab/python-path-shebang

language/python: support `python3` from PATH in `#detected_python_shebang`

Library/Homebrew/language/python.rb

@@ -103,16 +103,22 @@ module Language
         )
       end
 
-      def detected_python_shebang(formula = self)
-        python_deps = formula.deps.map(&:name).grep(/^python(@.*)?$/)
+      def detected_python_shebang(formula = self, use_python_from_path: false)
+        python_path = if use_python_from_path
+          "/usr/bin/env python3"
+        else
+          python_deps = formula.deps.map(&:name).grep(/^python(@.*)?$/)
 
-        raise ShebangDetectionError.new("Python", "formula does not depend on Python") if python_deps.empty?
-        if python_deps.length > 1
-          raise ShebangDetectionError.new("Python", "formula has multiple Python dependencies")
+          raise ShebangDetectionError.new("Python", "formula does not depend on Python") if python_deps.empty?
+          if python_deps.length > 1
+            raise ShebangDetectionError.new("Python", "formula has multiple Python dependencies")
+          end
+
+          python_dep = python_deps.first
+          Formula[python_dep].opt_bin/python_dep.sub("@", "")
         end
 
-        python_dep = python_deps.first
-        python_shebang_rewrite_info(Formula[python_dep].opt_bin/python_dep.sub("@", ""))
+        python_shebang_rewrite_info(python_path)
       end
     end
 

Library/Homebrew/test/language/python/shebang_spec.rb

@@ -21,7 +21,7 @@ describe Language::Python::Shebang do
 
   before do
     file.write <<~EOS
-      #!/usr/bin/env python3
+      #!/usr/bin/python2
       a
       b
       c
@@ -34,7 +34,7 @@ describe Language::Python::Shebang do
   describe "#detected_python_shebang" do
     it "can be used to replace Python shebangs" do
       expect(Formulary).to receive(:factory).with(python_f.name).and_return(python_f)
-      Utils::Shebang.rewrite_shebang described_class.detected_python_shebang(f), file
+      Utils::Shebang.rewrite_shebang described_class.detected_python_shebang(f, use_python_from_path: false), file
 
       expect(File.read(file)).to eq <<~EOS
         #!#{HOMEBREW_PREFIX}/opt/python@3.11/bin/python3.11
@@ -43,5 +43,16 @@ describe Language::Python::Shebang do
         c
       EOS
     end
+
+    it "can be pointed to a `python3` in PATH" do
+      Utils::Shebang.rewrite_shebang described_class.detected_python_shebang(f, use_python_from_path: true), file
+
+      expect(File.read(file)).to eq <<~EOS
+        #!/usr/bin/env python3
+        a
+        b
+        c
+      EOS
+    end
   end
 end