[close #42] Annotate NoMethodError

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## HEAD (unreleased)
 
-- Do not count trailing if/unless as a kewyword (https://github.com/zombocom/dead_end/pull/44)
+- Annotate NoMethodError in non-production environments (https://github.com/zombocom/dead_end/pull/46)
+- Do not count trailing if/unless as a keyword (https://github.com/zombocom/dead_end/pull/44)
 
 ## 1.0.2
 

README.md

@@ -1,6 +1,6 @@
 # DeadEnd
 
-An AI powered library to find syntax errors in your source code:
+An error in your code forces you to stop. DeadEnd helps you find those errors to get you back on your way faster.
 
     DeadEnd: Unmatched `end` detected
 
@@ -18,7 +18,7 @@ An AI powered library to find syntax errors in your source code:
 
 ## Installation in your codebase
 
-To automatically search syntax errors when they happen, add this to your Gemfile:
+To automatically annotate errors when they happen, add this to your Gemfile:
 
 ```ruby
 gem 'dead_end'
@@ -44,7 +44,7 @@ If you're using rspec add this to your `.rspec` file:
 
 ## Install the CLI
 
-To get the CLI and manually search for syntax errors, install the gem:
+To get the CLI and manually search for syntax errors (but not automatically annotate them), you can manually install the gem:
 
     $ gem install dead_end
 
@@ -54,7 +54,7 @@ This gives you the CLI command `$ dead_end` for more info run `$ dead_end --help
 
 - Missing `end`:
 
-```
+```ruby
 class Dog
   def bark
     puts "bark"
@@ -68,7 +68,7 @@ end
 
 - Unexpected `end`
 
-```
+```ruby
 class Dog
   def speak
     @sounds.each |sound| # Note the missing `do` here
@@ -81,6 +81,21 @@ end
 
 As well as unmatched `|` and unmatched `}`. These errors can be time consuming to debug because Ruby often only tells you the last line in the file. The command `ruby -wc path/to/file.rb` can narrow it down a little bit, but this library does a better job.
 
+## What other errors does it handle?
+
+In addition to syntax errors, the NoMethodError is annotated to show the line where the error occured, and the surrounding context:
+
+```
+scratch.rb:7:in `call': undefined method `upcase' for nil:NilClass (NoMethodError)
+
+
+  1  class Pet
+  6    def call
+❯ 7      puts "Come here #{@neam.upcase}"
+  8    end
+  9  end
+```
+
 ## Sounds cool, but why isn't this baked into Ruby directly?
 
 I would love to get something like this directly in Ruby, but I first need to prove it's useful. The `did_you_mean` functionality started as a gem that was eventually adopted by a bunch of people and then Ruby core liked it enough that they included it in the source. The goal of this gem is to:
@@ -90,7 +105,7 @@ I would love to get something like this directly in Ruby, but I first need to pr
 
 ## Artificial Inteligence?
 
-This library uses a goal-seeking algorithm similar to that of a path-finding search. For more information [read the blog post about how it works under the hood](https://schneems.com/2020/12/01/squash-unexpectedend-errors-with-syntaxsearch/).
+This library uses a goal-seeking algorithm for syntax error detection similar to that of a path-finding search. For more information [read the blog post about how it works under the hood](https://schneems.com/2020/12/01/squash-unexpectedend-errors-with-syntaxsearch/).
 
 ## How does it detect syntax error locations?
 

lib/dead_end/auto.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+#
 require_relative "../dead_end/internals"
 
 # Monkey patch kernel to ensure that all `require` calls call the same
@@ -49,3 +51,49 @@ def require(path)
   end
 end
 
+module DeadEnd
+  IsProduction = -> {
+    ENV["RAILS_ENV"] == "production" || ENV["RACK_ENV"] == "production"
+  }
+end
+
+# Unlike a syntax error, a NoMethodError can occur hundreds or thousands of times and
+# chew up CPU and other resources. Since this is primarilly a "development" optimization
+# we can attempt to disable this behavior in a production context.
+if !DeadEnd::IsProduction.call
+  class NoMethodError
+    def to_s
+      return super if DeadEnd::IsProduction.call
+
+      file, line, _ = backtrace[0].split(":")
+      return super if !File.exist?(file)
+
+      index = line.to_i - 1
+      source = File.read(file)
+      code_lines = DeadEnd::CodeLine.parse(source)
+
+      block = DeadEnd::CodeBlock.new(lines: code_lines[index])
+      lines = DeadEnd::CaptureCodeContext.new(
+        blocks: block,
+        code_lines: code_lines
+      ).call
+
+      message = super.dup
+      message << $/
+      message << $/
+
+      message << DeadEnd::DisplayCodeWithLineNumbers.new(
+        lines: lines,
+        highlight_lines: block.lines,
+        terminal: self.class.to_tty?
+      ).call
+
+      message << $/
+      message
+    rescue => e
+      puts "DeadEnd Internal error: #{e.message}"
+      puts "DeadEnd Internal backtrace: #{e.backtrace}"
+      super
+    end
+  end
+end

lib/dead_end/code_line.rb

@@ -31,6 +31,12 @@ module DeadEnd
   class CodeLine
     TRAILING_SLASH = ("\\" + $/).freeze
 
+    def self.parse(source)
+      source.lines.map.with_index do |line, index|
+        CodeLine.new(line: line, index: index)
+      end
+    end
+
     attr_reader :line, :index, :indent, :original_line
 
     def initialize(line: , index:)

spec/integration/ruby_command_line_spec.rb

@@ -4,6 +4,52 @@
 
 module DeadEnd
   RSpec.describe "Requires with ruby cli" do
+    it "annotates NoMethodError" do
+      Dir.mktmpdir do |dir|
+        @tmpdir = Pathname(dir)
+        @script = @tmpdir.join("script.rb")
+        @script.write <<~'EOM'
+          class Pet
+            def initialize
+              @name = "cinco"
+            end
+
+            def call
+              puts "Come here #{@neam.upcase}"
+            end
+          end
+
+          Pet.new.call
+        EOM
+
+        out = `ruby -I#{lib_dir} -rdead_end/auto #{@script} 2>&1`
+
+        error_line = <<~'EOM'
+          ❯ 7      puts "Come here #{@neam.upcase}"
+        EOM
+
+        expect(out).to include("NoMethodError")
+        expect(out).to include(error_line)
+        expect(out).to include(<<~'EOM')
+            1  class Pet
+            6    def call
+          ❯ 7      puts "Come here #{@neam.upcase}"
+            8    end
+            9  end
+        EOM
+        expect($?.success?).to be_falsey
+
+        # Test production check
+        out = `RAILS_ENV=production ruby -I#{lib_dir} -rdead_end/auto #{@script} 2>&1`
+        expect(out).to include("NoMethodError")
+        expect(out).to_not include(error_line)
+
+        out = `RACK_ENV=production ruby -I#{lib_dir} -rdead_end/auto #{@script} 2>&1`
+        expect(out).to include("NoMethodError")
+        expect(out).to_not include(error_line)
+      end
+    end
+
     it "detects require error and adds a message with auto mode" do
       Dir.mktmpdir do |dir|
         @tmpdir = Pathname(dir)