Share same template quasi array with all identical calls

bublejs · Dec 5, 2017 · 6272cc0 · 6272cc0
1 parent 2db8c74
commit 6272cc0
Show file tree

Hide file tree

Showing 3 changed files with 19 additions and 4 deletions.
diff --git a/src/program/Program.js b/src/program/Program.js
@@ -18,6 +18,8 @@ export default function Program(source, ast, transforms, options) {
 	wrap((this.body = ast), this);
 	this.body.__proto__ = BlockStatement.prototype;
 
+	this.templateLiteralQuasis = Object.create(null);
+
 	this.indentExclusionElements = [];
 	this.body.initialise(transforms);
 

diff --git a/src/program/types/TaggedTemplateExpression.js b/src/program/types/TaggedTemplateExpression.js
@@ -22,15 +22,21 @@ export default class TaggedTemplateExpression extends Node {
 				.concat(this.quasi.quasis)
 				.sort((a, b) => a.start - b.start);
 
-			const root = this.findNearest('Program');
+			const program = this.program;
+			const rootScope = program.body.scope;
 
 			// insert strings at start
 			const templateStrings = this.quasi.quasis.map(quasi =>
 				JSON.stringify(quasi.value.cooked)
-			);
+			).join(', ');
+
+			let templateObject = this.program.templateLiteralQuasis[templateStrings];
+			if (!templateObject) {
+				templateObject = rootScope.createIdentifier('templateObject');
+				code.prependRight(0, `var ${templateObject} = Object.freeze([${templateStrings}]);\n`);
 
-			const templateObject = root.scope.createIdentifier('templateObject');
-			code.prependRight(0, `var ${templateObject} = Object.freeze([${templateStrings.join(', ')}]);\n`);
+				this.program.templateLiteralQuasis[templateStrings] = templateObject;
+			}
 
 			code.overwrite(
 				this.tag.end,

diff --git a/test/samples/template-strings.js b/test/samples/template-strings.js
@@ -52,6 +52,13 @@ module.exports = [
 		output: `var templateObject = Object.freeze(["", "y"]);\nvar str = x(templateObject, (function () { return 42; })());`
 	},
 
+	{
+		description: 'reuses quasi array for identical tagged template strings',
+		options: { transforms: { dangerousTaggedTemplateString: true } },
+		input: 'x`a${a}b`, x`a${b}b`, x`b${c}a`',
+		output: `var templateObject$1 = Object.freeze(["b", "a"]);\nvar templateObject = Object.freeze(["a", "b"]);\nx(templateObject, a), x(templateObject, b), x(templateObject$1, c)`
+	},
+
 	{
 		description: 'parenthesises template strings as necessary',
 		input: 'var str = `x${y}`.toUpperCase();',