shebangs: fix broken shebangs like #!python

Library/Homebrew/language/node.rb

@@ -96,7 +96,7 @@ module Shebang
       module_function
 
       # A regex to match potential shebang permutations.
-      NODE_SHEBANG_REGEX = %r{^#! ?/usr/bin/(?:env )?node( |$)}
+      NODE_SHEBANG_REGEX = %r{^#! ?(?:/usr/bin/(?:env )?)?node( |$)}
 
       # The length of the longest shebang matching `SHEBANG_REGEX`.
       NODE_SHEBANG_MAX_LENGTH = T.let("#! /usr/bin/env node ".length, Integer)

Library/Homebrew/language/perl.rb

@@ -15,7 +15,7 @@ module Shebang
       module_function
 
       # A regex to match potential shebang permutations.
-      PERL_SHEBANG_REGEX = %r{^#! ?/usr/bin/(?:env )?perl( |$)}
+      PERL_SHEBANG_REGEX = %r{^#! ?(?:/usr/bin/(?:env )?)?perl( |$)}
 
       # The length of the longest shebang matching `SHEBANG_REGEX`.
       PERL_SHEBANG_MAX_LENGTH = T.let("#! /usr/bin/env perl ".length, Integer)

Library/Homebrew/language/python.rb

@@ -112,7 +112,7 @@ module Shebang
       module_function
 
       # A regex to match potential shebang permutations.
-      PYTHON_SHEBANG_REGEX = %r{^#! ?/usr/bin/(?:env )?python(?:[23](?:\.\d{1,2})?)?( |$)}
+      PYTHON_SHEBANG_REGEX = %r{^#! ?(?:/usr/bin/(?:env )?)?python(?:[23](?:\.\d{1,2})?)?( |$)}
 
       # The length of the longest shebang matching `SHEBANG_REGEX`.
       PYTHON_SHEBANG_MAX_LENGTH = T.let("#! /usr/bin/env pythonx.yyy ".length, Integer)

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

@@ -5,6 +5,7 @@
 
 RSpec.describe Language::Node::Shebang do
   let(:file) { Tempfile.new("node-shebang") }
+  let(:broken_file) { Tempfile.new("node-shebang") }
   let(:f) do
     f = {}
 
@@ -40,9 +41,16 @@
       c
     EOS
     file.flush
+    broken_file.write <<~EOS
+      #!node
+      a
+      b
+      c
+    EOS
+    broken_file.flush
   end
 
-  after { file.unlink }
+  after { [file, broken_file].each(&:unlink) }
 
   describe "#detected_node_shebang" do
     it "can be used to replace Node shebangs" do
@@ -57,6 +65,18 @@
       EOS
     end
 
+    it "can fix broken shebang like `#!node`" do
+      allow(Formulary).to receive(:factory).with(f[:node18].name).and_return(f[:node18])
+      Utils::Shebang.rewrite_shebang described_class.detected_node_shebang(f[:versioned_node_dep]), broken_file.path
+
+      expect(File.read(broken_file)).to eq <<~EOS
+        #!#{HOMEBREW_PREFIX/"opt/node@18/bin/node"}
+        a
+        b
+        c
+      EOS
+    end
+
     it "errors if formula doesn't depend on node" do
       expect { Utils::Shebang.rewrite_shebang described_class.detected_node_shebang(f[:no_deps]), file.path }
         .to raise_error(ShebangDetectionError, "Cannot detect Node shebang: formula does not depend on Node.")

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

@@ -5,6 +5,7 @@
 
 RSpec.describe Language::Perl::Shebang do
   let(:file) { Tempfile.new("perl-shebang") }
+  let(:broken_file) { Tempfile.new("perl-shebang") }
   let(:f) do
     f = {}
 
@@ -39,9 +40,16 @@
       c
     EOS
     file.flush
+    broken_file.write <<~EOS
+      #!perl
+      a
+      b
+      c
+    EOS
+    broken_file.flush
   end
 
-  after { file.unlink }
+  after { [file, broken_file].each(&:unlink) }
 
   describe "#detected_perl_shebang" do
     it "can be used to replace Perl shebangs when depends_on \"perl\" is used" do
@@ -74,6 +82,24 @@
       EOS
     end
 
+    it "can fix broken shebang like `#!perl`" do
+      allow(Formulary).to receive(:factory).with(f[:perl].name).and_return(f[:perl])
+      Utils::Shebang.rewrite_shebang described_class.detected_perl_shebang(f[:uses_from_macos]), broken_file.path
+
+      expected_shebang = if OS.mac?
+        "/usr/bin/perl#{MacOS.preferred_perl_version}"
+      else
+        HOMEBREW_PREFIX/"opt/perl/bin/perl"
+      end
+
+      expect(File.read(broken_file)).to eq <<~EOS
+        #!#{expected_shebang}
+        a
+        b
+        c
+      EOS
+    end
+
     it "errors if formula doesn't depend on perl" do
       expect { Utils::Shebang.rewrite_shebang described_class.detected_perl_shebang(f[:no_deps]), file.path }
         .to raise_error(ShebangDetectionError, "Cannot detect Perl shebang: formula does not depend on Perl.")

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

@@ -5,6 +5,7 @@
 
 RSpec.describe Language::Python::Shebang do
   let(:file) { Tempfile.new("python-shebang") }
+  let(:broken_file) { Tempfile.new("python-shebang") }
   let(:f) do
     f = {}
 
@@ -40,9 +41,16 @@
       c
     EOS
     file.flush
+    broken_file.write <<~EOS
+      #!python
+      a
+      b
+      c
+    EOS
+    broken_file.flush
   end
 
-  after { file.unlink }
+  after { [file, broken_file].each(&:unlink) }
 
   describe "#detected_python_shebang" do
     it "can be used to replace Python shebangs" do
@@ -72,6 +80,20 @@
       EOS
     end
 
+    it "can fix broken shebang line `#!python`" do
+      Utils::Shebang.rewrite_shebang(
+        described_class.detected_python_shebang(f[:versioned_python_dep],
+                                                use_python_from_path: true), broken_file.path
+      )
+
+      expect(File.read(broken_file)).to eq <<~EOS
+        #!/usr/bin/env python3
+        a
+        b
+        c
+      EOS
+    end
+
     it "errors if formula doesn't depend on python" do
       expect do
         Utils::Shebang.rewrite_shebang(