Auto merge of #5100 - bronzdoc:fix_shebang_check_in_exec, r=segiddins

Warn if executable in bundle exec is empty

closes https://github.com/bundler/bundler/issues/5084

2 files changed, 21 insertions, 0 deletions

diff --git a/lib/bundler/cli/exec.rb b/lib/bundler/cli/exec.rb
index 4f238bbb59..62f7bc26cb 100644
--- a/lib/bundler/cli/exec.rb
+++ b/lib/bundler/cli/exec.rb
@@ -91,6 +91,12 @@ module Bundler
         "#!/usr/bin/env jruby\n",
         "#!#{Gem.ruby}\n",
       ]
+
+      if File.zero?(file)
+        Bundler.ui.warn "#{file} is empty"
+        return false
+      end
+
       first_line = File.open(file, "rb") {|f| f.read(possibilities.map(&:size).max) }
       possibilities.any? {|shebang| first_line.start_with?(shebang) }
     end
diff --git a/spec/commands/exec_spec.rb b/spec/commands/exec_spec.rb
index 4dc47919de..057310d89f 100644
--- a/spec/commands/exec_spec.rb
+++ b/spec/commands/exec_spec.rb
@@ -514,6 +514,21 @@ describe "bundle exec" do
       end
     end
 
+    context "the executable is empty" do
+      let(:executable) { "" }
+
+      let(:exit_code) { 0 }
+      let(:expected) { "#{path} is empty" }
+      let(:expected_err) { "" }
+      if LessThanProc.with(RUBY_VERSION).call("1.9")
+        # Kernel#exec in ruby < 1.9 will raise Errno::ENOEXEC if the command content is empty,
+        # even if the command is set as an executable.
+        pending "Kernel#exec is different"
+      else
+        it_behaves_like "it runs"
+      end
+    end
+
     context "the executable raises" do
       let(:executable) { super() << "\nraise 'ERROR'" }
       let(:exit_code) { 1 }