Respect operator precedence when serializing. (1f05c53a) · Commits · extjs / jsduck

lib/jsduck/serializer.rb

+86 −10

Original line number	Diff line number	Diff line
		@@ -97,31 +97,31 @@ module JsDuck
		# Expressions

		when "AssignmentExpression"
		to_s(ast["left"]) + " " + ast["operator"] + " " + to_s(ast["right"])
		parens(ast, ast["left"]) + " " + ast["operator"] + " " + to_s(ast["right"])

		when "ArrayExpression"
		"[" + list(ast["elements"]) + "]"

		when "BinaryExpression"
		to_s(ast["left"]) + " " + ast["operator"] + " " + to_s(ast["right"])
		binary(ast)

		when "CallExpression"
		call(ast)

		when "ConditionalExpression"
		to_s(ast["test"]) + " ? " + to_s(ast["consequent"]) + " : " + to_s(ast["alternate"])
		parens(ast, ast["test"]) + " ? " + to_s(ast["consequent"]) + " : " + to_s(ast["alternate"])

		when "FunctionExpression"
		function(ast)

		when "LogicalExpression"
		to_s(ast["left"]) + " " + ast["operator"] + " " + to_s(ast["right"])
		binary(ast)

		when "MemberExpression"
		if ast["computed"]
		to_s(ast["object"]) + "[" + to_s(ast["property"]) + "]"
		parens(ast, ast["object"]) + "[" + to_s(ast["property"]) + "]"
		else
		to_s(ast["object"]) + "." + to_s(ast["property"])
		parens(ast, ast["object"]) + "." + to_s(ast["property"])
		end

		when "NewExpression"
		@@ -140,13 +140,13 @@ module JsDuck
		"this"

		when "UnaryExpression"
		ast["operator"] + to_s(ast["argument"])
		ast["operator"] + parens(ast, ast["argument"])

		when "UpdateExpression"
		if ast["prefix"]
		ast["operator"] + to_s(ast["argument"])
		ast["operator"] + parens(ast, ast["argument"])
		else
		to_s(ast["argument"]) + ast["operator"]
		parens(ast, ast["argument"]) + ast["operator"]
		end

		# Basics
		@@ -162,6 +162,8 @@ module JsDuck
		end
		end

		private

		# serializes function declaration or expression
		def function(ast)
		params = list(ast["params"])
		@@ -176,8 +178,82 @@ module JsDuck

		# serializes call- and new-expression
		def call(ast)
		to_s(ast["callee"]) + "(" + list(ast["arguments"]) + ")"
		parens(ast, ast["callee"]) + "(" + list(ast["arguments"]) + ")"
		end

		# Handles both binary- and logical-expression
		def binary(ast)
		parens(ast, ast["left"]) + " " + ast["operator"] + " " + parens(ast, ast["right"])
		end

		# serializes child node and wraps it inside parenthesis if the
		# precedence rules compared to parent node would require so.
		def parens(parent, child)
		if precedence(parent) >= precedence(child)
		to_s(child)
		else
		"(" + to_s(child) + ")"
		end
		end

		# Returns the precedence of operator represented by given AST node
		def precedence(ast)
		p = PRECEDENCE[ast["type"]]
		if p.is_a? Fixnum
		p
		elsif p.is_a? Hash
		p[ast["operator"]]
		else
		0
		end
		end

		# Precedence rules of JavaScript operators.
		#
		# Taken from: https://developer.mozilla.org/en/JavaScript/Reference/Operators/Operator_Precedence
		#
		PRECEDENCE = {
		"SequenceExpression" => 17,
		"AssignmentExpression" => 16,
		"ConditionalExpression" => 15,
		"LogicalExpression" => {
		"\|\|" => 14,
		"&&" => 13,
		},
		"BinaryExpression" => {
		"\|" => 12,
		"^" => 11,
		"&" => 10,

		"==" => 9,
		"!=" => 9,
		"===" => 9,
		"!==" => 9,

		"<" => 8,
		"<=" => 8,
		">" => 8,
		">=" => 8,
		"in" => 8,
		"instanceof" => 8,

		"<<" => 7,
		">>" => 7,
		">>>" => 7,

		"+" => 6,
		"-" => 6,

		"*" => 5,
		"/" => 5,
		"%" => 5,
		},
		"UnaryExpression" => 4,
		"UpdateExpression" => 3,
		"CallExpression" => 2,
		"MemberExpression" => 1,
		"NewExpression" => 1,
		}

		end

spec/serializer_spec.rb

+37 −0

Original line number	Diff line number	Diff line
		@@ -131,7 +131,44 @@ describe JsDuck::Serializer do
		it "with statement" do
		test("with (obj) {}")
		end
		end

		describe "adds parenthesis correctly on" do
		it "assignment expression" do
		test("(foo, bar) = [1, 2];")
		end

		it "conditional expression" do
		test("(foo = true) ? 1 : 2;")
		end

		it "binary expression" do
		test("3 * (5 + 1);")
		end

		it "logical expression" do
		test("foo && (bar \|\| baz);")
		end

		it "unary expression" do
		test("!(bar \|\| baz);")
		end

		it "update expression" do
		test("++(5 + 5);")
		end

		it "call expression" do
		test("(foo \|\| bar)();")
		end

		it "member expression" do
		test("(foo \|\| bar).baz;")
		end

		it "new expression" do
		test("new (Foo \|\| Bar)();")
		end
		end

		end