Dev: Improve readability of debug output for eval

lib/init/eval.js

@@ -239,7 +239,7 @@ function compile(code, tracker, filename, isIndirectEval, state, isStrict) {
 	}
 
 	// Return instrumented code
-	code = generate(ast, {retainLines: true, compact: true}).code;
+	code = generateCode(ast); // eslint-disable-line no-use-before-define
 
 	if (DEBUG) {
 		/* eslint-disable no-console */
@@ -260,11 +260,8 @@ function wrapInFunction(ast, internalPrefixNum) {
 			internalVarNode(TRACKER_VAR_NAME_BODY, internalPrefixNum),
 			internalVarNode(GET_SCOPE_ID_VAR_NAME_BODY, internalPrefixNum)
 		],
-		t.callExpression(
-			t.identifier('eval'), [
-				t.stringLiteral(generate(ast, {retainLines: true, compact: true}).code)
-			]
-		)
+		// eslint-disable-next-line no-use-before-define
+		t.callExpression(t.identifier('eval'), [generateCodeStringNode(ast)])
 	);
 }
 
@@ -281,3 +278,28 @@ function wrapInFunctionCall(fnNode, externalPrefixNum) {
 function internalVarNode(name, prefixNum) {
 	return t.identifier(`${INTERNAL_VAR_NAMES_PREFIX}${prefixNum || ''}_${name}`);
 }
+
+/**
+ * Generate code from AST.
+ * If debugging enabled, generates in a more readable form.
+ * @param {Object} ast - AST
+ * @returns {string} - Generated code
+ */
+const generateCode = DEBUG
+	? ast => generate(ast).code
+	: ast => generate(ast, {retainLines: true, compact: true}).code;
+
+/**
+ * Generate a string literal AST node for a string of code generated from AST.
+ * If debugging enabled, generates a template literal instead with line breaks retained
+ * for greater readability.
+ * @param {Object} ast - AST
+ * @returns {Object} - String literal / template literal AST node
+ */
+const generateCodeStringNode = DEBUG
+	? ast => t.templateLiteral([
+		t.templateElement({
+			raw: `\n${generateCode(ast).replace(/\\/g, '\\\\').replace(/`/g, '\\`')}\n`
+		}, true)
+	], [])
+	: ast => t.stringLiteral(generateCode(ast));