Precompute concatenated strings where possible

Author: ExE-Boss

lib/constructs/iterable.js

@@ -39,12 +39,10 @@ class Iterable {
           throw new TypeError("Illegal invocation");
         }
         if (arguments.length < 1) {
-          throw new TypeError("Failed to execute 'forEach' on '${this.name}': 1 argument required, " +
-                              "but only 0 present.");
+          throw new TypeError("Failed to execute 'forEach' on '${this.name}': 1 argument required, but only 0 present.");
         }
         if (typeof callback !== "function") {
-          throw new TypeError("Failed to execute 'forEach' on '${this.name}': The callback provided " +
-                              "as parameter 1 is not a function.");
+          throw new TypeError("Failed to execute 'forEach' on '${this.name}': The callback provided as parameter 1 is not a function.");
         }
         const thisArg = arguments[1];
         let pairs = Array.from(this[implSymbol]);

lib/parameters.js

@@ -22,7 +22,7 @@ function generateVarConversion(ctx, overload, i, parent, errPrefix, targetIdx =
     `;
   }
   const msg = typeof targetIdx === "string" ?
-    `"${errPrefix}parameter " + (${targetIdx} + 1)` : `"${errPrefix}parameter ${i + 1}"`;
+    `\`${errPrefix}parameter \${${targetIdx} + 1}\`` : `"${errPrefix}parameter ${i + 1}"`;
   const conv = Types.generateTypeConversion(
     ctx, "curArg", idlType, [], parent.name, msg);
   requires.merge(conv.requires);
@@ -58,8 +58,7 @@ module.exports.generateOverloadConversions = function (ctx, typeOfOp, name, pare
       const plural = minArgs > 1 ? "s" : "";
       str += `
         if (arguments.length < ${minArgs}) {
-          throw new TypeError("${errPrefix}${minArgs} argument${plural} required, but only " + arguments.length +
-                              " present.");
+          throw new TypeError(\`${errPrefix}${minArgs} argument${plural} required, but only \${arguments.length} present.\`);
         }
       `;
     }
@@ -72,7 +71,7 @@ module.exports.generateOverloadConversions = function (ctx, typeOfOp, name, pare
         .filter(o => o.typeList.length === numArgs);
       if (S.length === 0) {
         switchCases.push(`
-          throw new TypeError("${errPrefix}only " + arguments.length + " arguments present.");
+          throw new TypeError(\`${errPrefix}only \${arguments.length} arguments present.\`);
         `);
         continue;
       }

lib/types.js

@@ -83,6 +83,18 @@ function deepClone(obj) {
   return JSON.parse(JSON.stringify(obj));
 }
 
+function appendToErrorPrefix(errPrefix, appended) {
+  if (errPrefix.endsWith('"')) {
+    return errPrefix.slice(0, -1) + appended + '"';
+  } else if (errPrefix.endsWith("'")) {
+    return errPrefix.slice(0, -1) + appended + "'";
+  } else if (errPrefix.endsWith("`")) {
+    return errPrefix.slice(0, -1) + appended + "`";
+  }
+
+  return `\`\${${errPrefix}}${appended}\``;
+}
+
 function generateTypeConversion(ctx, name, idlType, argAttrs = [], parentName, errPrefix = '"The provided value"') {
   const requires = new utils.RequiresMap(ctx);
   let str = "";
@@ -211,25 +223,25 @@ function generateTypeConversion(ctx, name, idlType, argAttrs = [], parentName, e
       if (union.sequenceLike) {
         code += `if (${name}[Symbol.iterator] !== undefined) {`;
         const conv = generateTypeConversion(ctx, name, union.sequenceLike, [], parentName,
-          `${errPrefix} + " sequence"`);
+          appendToErrorPrefix(errPrefix, " sequence"));
         requires.merge(conv.requires);
         code += conv.body;
         code += `} else {`;
       }
 
       if (union.dictionary) {
         const conv = generateTypeConversion(ctx, name, union.dictionary, [], parentName,
-          `${errPrefix} + " dictionary"`);
+          appendToErrorPrefix(errPrefix, " dictionary"));
         requires.merge(conv.requires);
         code += conv.body;
       } else if (union.record) {
         const conv = generateTypeConversion(ctx, name, union.record, [], parentName,
-          `${errPrefix} + " record"`);
+          appendToErrorPrefix(errPrefix, " record"));
         requires.merge(conv.requires);
         code += conv.body;
       } else if (union.callbackInterface) {
         const conv = generateTypeConversion(ctx, name, union.callbackInterface, [], parentName,
-          `${errPrefix} + " callback interface"`);
+          appendToErrorPrefix(errPrefix, " callback interface"));
         requires.merge(conv.requires);
         code += conv.body;
       } else if (union.object) {
@@ -269,7 +281,7 @@ function generateTypeConversion(ctx, name, idlType, argAttrs = [], parentName, e
         code += conv.body;
         requires.merge(conv.requires);
       } else {
-        code += `throw new TypeError(${errPrefix} + " is not of any supported type.")`;
+        code += `throw new TypeError(${appendToErrorPrefix(errPrefix, " is not of any supported type.")})`;
       }
       code += "}";
       output.push(code);
@@ -280,12 +292,12 @@ function generateTypeConversion(ctx, name, idlType, argAttrs = [], parentName, e
 
   function generateSequence() {
     const conv = generateTypeConversion(ctx, "nextItem", idlType.idlType[0], [], parentName,
-      `${errPrefix} + "'s element"`);
+      appendToErrorPrefix(errPrefix, "'s element"));
     requires.merge(conv.requires);
 
     str += `
       if (!utils.isObject(${name})) {
-        throw new TypeError(${errPrefix} + " is not an iterable object.");
+        throw new TypeError(${appendToErrorPrefix(errPrefix, " is not an iterable object.")});
       } else {
         const V = [];
         const tmp = ${name};
@@ -300,15 +312,15 @@ function generateTypeConversion(ctx, name, idlType, argAttrs = [], parentName, e
 
   function generateRecord() {
     const keyConv = generateTypeConversion(ctx, "typedKey", idlType.idlType[0], [], parentName,
-      `${errPrefix} + "'s key"`);
+      appendToErrorPrefix(errPrefix, "'s key"));
     requires.merge(keyConv.requires);
     const valConv = generateTypeConversion(ctx, "typedValue", idlType.idlType[1], [], parentName,
-      `${errPrefix} + "'s value"`);
+      appendToErrorPrefix(errPrefix, "'s value"));
     requires.merge(valConv.requires);
 
     str += `
       if (!utils.isObject(${name})) {
-        throw new TypeError(${errPrefix} + " is not an object.");
+        throw new TypeError(${appendToErrorPrefix(errPrefix, " is not an object.")});
       } else {
         const result = Object.create(null);
         for (const key of Reflect.ownKeys(${name})) {
@@ -334,7 +346,7 @@ function generateTypeConversion(ctx, name, idlType, argAttrs = [], parentName, e
       handler = "";
     } else {
       const conv = generateTypeConversion(ctx, "value", idlType.idlType[0], [], parentName,
-        `${errPrefix} + " promise value"`);
+        appendToErrorPrefix(errPrefix, " promise value"));
       requires.merge(conv.requires);
       handler = `
         ${conv.body}