Increase allowed nesting depth of JSON

I turned up some instances of files that killed the engine due to
deeply nested JSON results from the parser: the JSON gem by default puts
a limit on this.

It did not feel appropriate to make the allowed depth unlimited, since
the JSON does result from parsing of unkown source files, and hence
probably should not be considered entirely trustworthy. But the default
limit of 100 also seems too low.

So this a 2-part approach to mitigating this problem:

1. Dramatically increase the limit used in parsers to 500
2. Catch the exception as a skippable exception so any exceptional cases
won't crash everything.

Author: wfleming

lib/cc/engine/analyzers/analyzer_base.rb

@@ -1,4 +1,5 @@
 require "cc/engine/analyzers/parser_error"
+require "cc/engine/analyzers/parser_base"
 
 module CC
   module Engine
@@ -7,6 +8,7 @@ class Base
         RESCUABLE_ERRORS = [
           ::CC::Engine::Analyzers::ParserError,
           ::Errno::ENOENT,
+          ::JSON::NestingError,
           ::Racc::ParseError,
           ::RubyParser::SyntaxError,
           ::RuntimeError,

lib/cc/engine/analyzers/javascript/parser.rb

@@ -4,7 +4,7 @@ module CC
   module Engine
     module Analyzers
       module Javascript
-        class Parser
+        class Parser < ParserBase
           attr_reader :code, :filename, :syntax_tree
 
           def initialize(code, filename)
@@ -15,8 +15,7 @@ def initialize(code, filename)
           def parse
             runner = CommandLineRunner.new(js_command)
             runner.run(strip_shebang(code)) do |ast|
-              json_ast = JSON.parse(ast)
-              @syntax_tree = json_ast
+              @syntax_tree = parse_json(ast)
             end
 
             self

lib/cc/engine/analyzers/parser_base.rb

@@ -0,0 +1,15 @@
+module CC
+  module Engine
+    module Analyzers
+      class ParserBase
+        MAX_JSON_NESTING = 500
+
+        protected
+
+        def parse_json(text)
+          JSON.parse(text, max_nesting: MAX_JSON_NESTING)
+        end
+      end
+    end
+  end
+end

lib/cc/engine/analyzers/php/parser.rb

@@ -6,7 +6,7 @@ module CC
   module Engine
     module Analyzers
       module Php
-        class Parser
+        class Parser < ParserBase
           attr_reader :code, :filename, :syntax_tree
 
           def initialize(code, filename)
@@ -17,7 +17,7 @@ def initialize(code, filename)
           def parse
             runner = CommandLineRunner.new("php #{parser_path}")
             runner.run(code) do |output|
-              json = JSON.parse(output)
+              json = parse_json(output)
 
               @syntax_tree = CC::Engine::Analyzers::Php::Nodes::Node.new.tap do |node|
                 node.stmts = CC::Engine::Analyzers::Php::AST.json_to_ast(json, filename)

lib/cc/engine/analyzers/python/parser.rb

@@ -6,7 +6,7 @@ module CC
   module Engine
     module Analyzers
       module Python
-        class Parser
+        class Parser < ParserBase
           attr_reader :code, :filename, :syntax_tree
 
           def initialize(code, filename)
@@ -17,8 +17,7 @@ def initialize(code, filename)
           def parse
             runner = CommandLineRunner.new(python_command)
             runner.run(code) do |ast|
-              json_ast = JSON.parse(ast)
-              @syntax_tree = json_ast
+              @syntax_tree = parse_json(ast)
             end
 
             self

spec/cc/engine/analyzers/php/main_spec.rb

@@ -49,6 +49,13 @@
       expect(json["fingerprint"]).to eq("667da0e2bab866aa2fe9d014a65d57d9")
     end
 
+    it "runs against complex files" do
+      FileUtils.cp(fixture_path("symfony_configuration.php"), File.join(@code, "configuration.php"))
+      result = run_engine(engine_conf).strip
+
+      expect(result).to match "\"type\":\"issue\""
+    end
+
     it "skips unparsable files" do
       create_source_file("foo.php", <<-EOPHP)
         <?php blorb &; "fee