Do not generate todo file there are no issues

spec/ameba/formatter/todo_formatter_spec.cr

@@ -1,28 +1,45 @@
 require "../../spec_helper"
+require "file_utils"
 
 module Ameba
   private def create_todo
-    file = IO::Memory.new
-    formatter = Formatter::TODOFormatter.new IO::Memory.new, file
-
+    formatter = Formatter::TODOFormatter.new IO::Memory.new
     s = Source.new "a = 1", "source.cr"
     s.add_issue DummyRule.new, {1, 2}, "message"
-
-    formatter.finished [s]
-    file.to_s
+    file = formatter.finished([s])
+    file ? File.read(file.path) : ""
   end
 
   describe Formatter::TODOFormatter do
+    Spec.after_each do
+      FileUtils.rm(Ameba::Config::PATH) if File.exists?(Ameba::Config::PATH)
+    end
+
     context "problems not found" do
-      it "does not create todo" do
-        file = IO::Memory.new
-        formatter = Formatter::TODOFormatter.new IO::Memory.new, file
+      it "does not create file" do
+        formatter = Formatter::TODOFormatter.new IO::Memory.new
+        file = formatter.finished [Source.new ""]
+        file.should be_nil
+      end
+
+      it "reports a message saying file is not created" do
+        io = IO::Memory.new
+        formatter = Formatter::TODOFormatter.new io
         formatter.finished [Source.new ""]
-        file.to_s.empty?.should be_true
+        io.to_s.should contain "No issues found. File is not generated"
       end
     end
 
     context "problems found" do
+      it "prints a message saying file is created" do
+        io = IO::Memory.new
+        formatter = Formatter::TODOFormatter.new io
+        s = Source.new "a = 1", "source.cr"
+        s.add_issue DummyRule.new, {1, 2}, "message"
+        formatter.finished([s])
+        io.to_s.should contain "Created .ameba.yml"
+      end
+
       it "creates a valid YAML document" do
         YAML.parse(create_todo).should_not be_nil
       end
@@ -60,17 +77,24 @@ module Ameba
       end
 
       context "when invalid syntax" do
-        it "does not exclude Syntax rule" do
-          file = IO::Memory.new
-          formatter = Formatter::TODOFormatter.new IO::Memory.new, file
+        it "does generate todo file" do
+          formatter = Formatter::TODOFormatter.new IO::Memory.new
+          s = Source.new "def invalid_syntax"
+          s.add_issue Rule::Lint::Syntax.new, {1, 2}, "message"
 
+          file = formatter.finished [s]
+          file.should be_nil
+        end
+
+        it "prints an error message" do
+          io = IO::Memory.new
+          formatter = Formatter::TODOFormatter.new io
           s = Source.new "def invalid_syntax"
           s.add_issue Rule::Lint::Syntax.new, {1, 2}, "message"
 
           formatter.finished [s]
-          content = file.to_s
-
-          content.should_not contain "Syntax"
+          io.to_s.should contain "Unable to generate TODO file"
+          io.to_s.should contain "Please fix syntax issues"
         end
       end
     end

src/ameba/formatter/todo_formatter.cr

@@ -3,29 +3,38 @@ module Ameba::Formatter
   # Basically, it takes all issues reported and disables corresponding rules
   # or excludes failed sources from these rules.
   class TODOFormatter < DotFormatter
-    @io : IO::FileDescriptor | IO::Memory
-
-    def initialize(@output = STDOUT, @io = File.new(Config::PATH, mode: "w"))
+    def initialize(@output = STDOUT)
     end
 
     def finished(sources)
       super
       issues = sources.map(&.issues).flatten
-      generate_todo_config issues if issues.any?
-      if (io = @io).is_a?(File)
-        @output << "Created #{io.path}\n"
+      unless issues.any? { |issue| !issue.disabled? }
+        @output << "No issues found. File is not generated.\n"
+        return
+      end
+
+      if issues.any? { |issue| issue.syntax? }
+        @output << "Unable to generate TODO file. Please fix syntax issues.\n"
+        return
       end
+
+      file = generate_todo_config issues
+      @output << "Created #{file.path}\n"
+      file
     end
 
     private def generate_todo_config(issues)
-      @io << header
+      file = File.new(Config::PATH, mode: "w")
+      file << header
       rule_issues_map(issues).each do |rule, rule_issues|
-        @io << "\n# Problems found: #{rule_issues.size}"
-        @io << "\n# Run `ameba --only #{rule.name}` for details"
-        @io << rule_todo(rule, rule_issues).gsub("---", "")
+        file << "\n# Problems found: #{rule_issues.size}"
+        file << "\n# Run `ameba --only #{rule.name}` for details"
+        file << rule_todo(rule, rule_issues).gsub("---", "")
       end
+      file
     ensure
-      @io.flush
+      file.close if file
     end
 
     private def rule_issues_map(issues)

src/ameba/issue.cr

@@ -18,5 +18,9 @@ module Ameba
     def disabled?
       status == :disabled
     end
+
+    def syntax?
+      rule.is_a?(Rule::Lint::Syntax)
+    end
   end
 end