fix: output an informative error when the gemspec parsed is not valid…

… Ruby

lib/bundler/gem_bytes/actions.rb

@@ -27,7 +27,7 @@ def add_dependency(dependency_type, gem_name, version_constraint, force: false,
         source = File.read(gemspec)
         updated_source = Bundler::GemBytes::Gemspec::UpsertDependency.new(
           dependency_type, gem_name, version_constraint, force: force
-        ).call(source)
+        ).call(source, path: gemspec)
         File.write(gemspec, updated_source)
       end
     end

lib/bundler/gem_bytes/gemspec/upsert_dependency.rb

@@ -101,6 +101,9 @@ def initialize(dependency_type, gem_name, version_constraint, force: false)
         # Returns the content of the gemspec file with the new/updated dependency
         #
         # @param code [String] The content of the gemspec file
+        # @param path [String] This should be the path to the gemspspec file
+        #
+        #   path is used to generate error messages only
         #
         # @return [String] The updated gemspec content with the new/added dependency
         #
@@ -112,12 +115,9 @@ def initialize(dependency_type, gem_name, version_constraint, force: false)
         #   updated_code = add_dependency.call(code)
         #   puts updated_code
         #
-        #
-        def call(code)
-          ast = RuboCop::AST::ProcessedSource.new(code, ruby_version).ast
-          buffer = Parser::Source::Buffer.new('(string)', source: code)
+        def call(code, path: '(string)')
           @found_gemspec_block = false
-          rewrite(buffer, ast).tap do |_result|
+          rewrite(*parse(code, path)).tap do |_result|
             raise ArgumentError, 'Gem::Specification block not found' unless found_gemspec_block
           end
         end
@@ -161,6 +161,22 @@ def on_send(node)
 
         private
 
+        # Parses the given code into an AST
+        # @param code [String] The code to parse
+        # @param path [String] The path to the file being parsed (used for error messages only)
+        # @return [Array<Parser::AST::Node, Parser::Source::Buffer>] The AST and buffer
+        # @api private
+        def parse(code, path)
+          buffer = Parser::Source::Buffer.new(path, source: code)
+          processed_source = RuboCop::AST::ProcessedSource.new(code, ruby_version, path)
+          unless processed_source.valid_syntax?
+            raise "Invalid syntax in #{path}\n#{processed_source.diagnostics.map(&:render).join("\n")}"
+          end
+
+          ast = processed_source.ast
+          [buffer, ast]
+        end
+
         # Adds or updates the given dependency in the Gem::Specification block
         # @param node [Parser::AST::Node] The block node within the AST
         # @return [void]

spec/features/actions_steps.rb

@@ -32,7 +32,7 @@ def command_err = @command_err
 def command_status = @command_status
 # rubocop:enable Style/TrivialAccessors
 
-def run_command(command, raise_on_fail: true, failure_message: "#{command[0]} failed")
+def run_command(command, raise_on_failure: true, failure_message: "#{command[0]} failed")
   out_buffer = StringIO.new
   out_pipe = ProcessExecuter::MonitoredPipe.new(out_buffer)
   err_buffer = StringIO.new
@@ -43,7 +43,7 @@ def run_command(command, raise_on_fail: true, failure_message: "#{command[0]} fa
     @command_err = err_buffer.string
     @command_status = status
 
-    raise "#{failure_message}: #{command_err}" if raise_on_fail && !command_status.success?
+    raise "#{failure_message}: #{command_err}" if raise_on_failure && !command_status.success?
   end
 end
 
@@ -74,7 +74,7 @@ def run_command(command, raise_on_fail: true, failure_message: "#{command[0]} fa
 
 step 'I run :command' do |command|
   Dir.chdir(gem_project_dir) do
-    run_command(command.split, fail_on_error: false)
+    run_command(command.split, raise_on_failure: false)
   end
 end
 

spec/lib/bundler/gem_bytes/gemspec/upsert_dependency_spec.rb

@@ -54,6 +54,16 @@
   describe '#call' do
     subject { instance.call(gemspec) }
 
+    context 'when the gemspec is not valid Ruby code' do
+      let(:gemspec) { <<~GEMSPEC }
+        This is not valid Ruby code. Please fix this file to continue.
+      GEMSPEC
+
+      it 'raises an error' do
+        expect { subject }.to raise_error(RuntimeError, /Invalid syntax in \(string\)/)
+      end
+    end
+
     context 'when the gemspec does not contain a Gem::Specification block' do
       let(:gemspec) { <<~GEMSPEC }
         puts 'Hello, world!'