Merge pull request #527 from Shopify/at-deadcode-prism

Migrate dead code detection to Prism

Gemfile.lock

@@ -3,8 +3,8 @@ PATH
   specs:
     spoom (1.2.4)
       erubi (>= 1.10.0)
+      prism (>= 0.19.0)
       sorbet-static-and-runtime (>= 0.5.10187)
-      syntax_tree (>= 6.1.1)
       thor (>= 0.19.2)
 
 GEM
@@ -34,7 +34,6 @@ GEM
     parser (3.3.0.5)
       ast (~> 2.4.1)
       racc
-    prettier_print (1.2.1)
     prism (0.19.0)
     psych (5.1.2)
       stringio
@@ -77,8 +76,6 @@ GEM
       sorbet (= 0.5.11287)
       sorbet-runtime (= 0.5.11287)
     stringio (3.1.0)
-    syntax_tree (6.2.0)
-      prettier_print (>= 1.2.0)
     tapioca (0.12.0)
       bundler (>= 2.2.25)
       netrc (>= 0.11.0)

lib/spoom/deadcode.rb

@@ -2,8 +2,9 @@
 # frozen_string_literal: true
 
 require "erubi"
-require "syntax_tree"
+require "prism"
 
+require_relative "deadcode/visitor"
 require_relative "deadcode/erb"
 require_relative "deadcode/index"
 require_relative "deadcode/indexer"
@@ -18,10 +19,15 @@
 module Spoom
   module Deadcode
     class Error < Spoom::Error
-      extend T::Sig
       extend T::Helpers
 
       abstract!
+    end
+
+    class ParserError < Error; end
+
+    class IndexerError < Error
+      extend T::Sig
 
       sig { params(message: String, parent: Exception).void }
       def initialize(message, parent:)
@@ -30,23 +36,29 @@ def initialize(message, parent:)
       end
     end
 
-    class ParserError < Error; end
-    class IndexerError < Error; end
-
     class << self
       extend T::Sig
 
-      sig { params(ruby: String, file: String).returns(SyntaxTree::Node) }
+      sig { params(ruby: String, file: String).returns(Prism::Node) }
       def parse_ruby(ruby, file:)
-        SyntaxTree.parse(ruby)
-      rescue SyntaxTree::Parser::ParseError => e
-        raise ParserError.new("Error while parsing #{file} (#{e.message} at #{e.lineno}:#{e.column})", parent: e)
+        result = Prism.parse(ruby)
+        unless result.success?
+          message = +"Error while parsing #{file}:\n"
+
+          result.errors.each do |e|
+            message << "- #{e.message} (at #{e.location.start_line}:#{e.location.start_column})\n"
+          end
+
+          raise ParserError, message
+        end
+
+        result.value
       end
 
       sig do
         params(
           index: Index,
-          node: SyntaxTree::Node,
+          node: Prism::Node,
           ruby: String,
           file: String,
           plugins: T::Array[Deadcode::Plugins::Base],