Reserved: Move reserved words from the parser definition to the config

Author: Mingun

lib/parser.js

@@ -204,6 +204,9 @@ declare namespace ast {
 /** Current Peggy version in semver format. */
 export const VERSION: string;
 
+/** Default list of reserved words. Contains list of JavaScript reserved words */
+export const RESERVED_WORDS: string[];
+
 /**
  * The entry that maps object in the `source` property of error locations
  * to the actual source text of a grammar. That entries is necessary for
@@ -282,6 +285,11 @@ export namespace parser {
      * File object.
      */
     grammarSource?: any;
+    /**
+     * List of words that won't be allowed as label names. Using such word will
+     * produce a syntax error.
+     */
+    reservedWords: string[];
     /** The only acceptable rule is `"Grammar"`, all other values leads to the exception */
     startRule?: "Grammar";
   }
@@ -759,6 +767,13 @@ export interface Config {
    * to add their own pass.
    */
   passes: Stages;
+  /**
+   * List of words that won't be allowed as label names. Using such word will
+   * produce a syntax error. This property can be replaced by the plugin if
+   * it want to change list of reserved words. By default this list is equals
+   * to `RESERVED_WORDS`.
+   */
+  reservedWords: string[];
 }
 
 /** Interface for the Peggy extenders. */

lib/peg.d.ts

@@ -5,9 +5,52 @@ const compiler = require("./compiler");
 const parser = require("./parser");
 const VERSION = require("./version");
 
+const RESERVED_WORDS = [
+  "break",
+  "case",
+  "catch",
+  "class",
+  "const",
+  "continue",
+  "debugger",
+  "default",
+  "delete",
+  "do",
+  "else",
+  "enum",
+  "export",
+  "extends",
+  "false",
+  "finally",
+  "for",
+  "function",
+  "if",
+  "import",
+  "instanceof",
+  "in",
+  "new",
+  "null",
+  "return",
+  "super",
+  "switch",
+  "this",
+  "throw",
+  "true",
+  "try",
+  "typeof",
+  "var",
+  "void",
+  "while",
+  "with"
+];
+
 const peg = {
   // Peggy version (filled in by /tools/release).
   VERSION,
+  /**
+   * Default list of reserved words.
+   */
+  RESERVED_WORDS,
   GrammarError,
   parser,
   compiler,
@@ -38,13 +81,17 @@ const peg = {
     const plugins = "plugins" in options ? options.plugins : [];
     const config = {
       parser: peg.parser,
-      passes: convertPasses(peg.compiler.passes)
+      passes: convertPasses(peg.compiler.passes),
+      reservedWords: peg.RESERVED_WORDS.slice(),
     };
 
     plugins.forEach(p => { p.use(config, options); });
 
     return peg.compiler.compile(
-      config.parser.parse(grammar, { grammarSource: options.grammarSource }),
+      config.parser.parse(grammar, {
+        grammarSource: options.grammarSource,
+        reservedWords: config.reservedWords,
+      }),
       config.passes,
       options
     );

lib/peg.js

@@ -38,48 +38,11 @@
     "&": "semantic_and",
     "!": "semantic_not"
   };
-
-  // Cannot use Set here because of native IE support.
-  const reservedWords = [
-    "break",
-    "case",
-    "catch",
-    "class",
-    "const",
-    "continue",
-    "debugger",
-    "default",
-    "delete",
-    "do",
-    "else",
-    "enum",
-    "export",
-    "extends",
-    "false",
-    "finally",
-    "for",
-    "function",
-    "if",
-    "import",
-    "instanceof",
-    "in",
-    "new",
-    "null",
-    "return",
-    "super",
-    "switch",
-    "this",
-    "throw",
-    "true",
-    "try",
-    "typeof",
-    "var",
-    "void",
-    "while",
-    "with"
-  ];
 }}
-
+{
+  // Cannot use Set here because of native IE support.
+  const reservedWords = options.reservedWords || [];
+}
 // ---- Syntactic Grammar -----
 
 Grammar

src/parser.pegjs

@@ -164,6 +164,34 @@ describe("Peggy API", function() {
 
     // The |plugins| option is tested in plugin API tests.
 
+    describe("reserved words", function() {
+      describe("throws an exception on reserved JS words used as a label", function() {
+        for (const label of peg.RESERVED_WORDS) {
+          it(label, function() {
+            expect(() => {
+              peg.generate([
+                "start = " + label + ":end",
+                "end = 'a'"
+              ].join("\n"), { output: "source" });
+            }).to.throw(peg.parser.SyntaxError);
+          });
+        }
+      });
+
+      describe("does not throws an exception on reserved JS words used as a rule name", function() {
+        for (const rule of peg.RESERVED_WORDS) {
+          it(rule, function() {
+            expect(() => {
+              peg.generate([
+                "start = " + rule,
+                rule + " = 'a'"
+              ].join("\n"), { output: "source" });
+            }).to.not.throw(peg.parser.SyntaxError);
+          });
+        }
+      });
+    });
+
     it("accepts custom options", function() {
       peg.generate("start = 'a'", { grammarSource: 42 });
     });