Make the default tracer an optional feature

docs/guides/javascript-api.md

@@ -97,7 +97,7 @@ cache | `false` | makes the generated parser cache results, avoiding exponential
 context | `{}` | contains a map of variables used by `peg.util.vm.runInContext()` when the `output` option is set to `"parser"`
 dependencies | `{}` | parser dependencies, the value is an object which maps variables used to access the dependencies to module IDs used to load them; valid only when `format` is set to `"amd"`, `"commonjs"`, `"es"`, or `"umd"`
 exportVar | `null` | name of an optional global variable into which the generated parser object is assigned to when no module loader is detected; valid only when `format` is set to `"globals"` or `"umd"`
-features | `null` | map of optional features that are set to `true` by default: `"text"`, `"offset"`, `"range"`, `"location"`, `"expected"`, `"error"` and `"filename"`
+features | `null` | map of optional features that are set to `true` by default: `"text"`, `"offset"`, `"range"`, `"location"`, `"expected"`, `"error"`, `"filename"` and `"DefaultTracer"`
 format | `"bare"` | format of the generated parser (`"amd"`, `"bare"`, `"commonjs"`, `"es"`, `"globals"`, or `"umd"`); valid only when `output` is set to `"source"`
 header | `null` | adds additional comments or content after the `Generated by ...` comment; this option is only handled if it's an array or a string:
 optimize | `"speed"` | selects between optimizing the generated parser for parsing speed (`"speed"`) or code size (`"size"`)

lib/compiler/passes/generate-js.js

@@ -1120,62 +1120,73 @@ function generateJS( ast, session, options ) {
 
         if ( options.trace ) {
 
-            parts.push( [
-                "function peg$DefaultTracer() {",
-                "  this.indentLevel = 0;",
-                "}",
-                "",
-                "peg$DefaultTracer.prototype.trace = function(event) {",
-                "  var that = this;",
-                "",
-                "  function log(event) {",
-                "    function repeat(string, n) {",
-                "       var result = \"\", i;",
-                "",
-                "       for (i = 0; i < n; i++) {",
-                "         result += string;",
-                "       }",
-                "",
-                "       return result;",
-                "    }",
-                "",
-                "    function pad(string, length) {",
-                "      return string + repeat(\" \", length - string.length);",
-                "    }",
-                "",
-                "    if (typeof console === \"object\") {",   // IE 8-10
-                "      console.log(",
-                "        event.location.start.line + \":\" + event.location.start.column + \"-\"",
-                "          + event.location.end.line + \":\" + event.location.end.column + \" \"",
-                "          + pad(event.type, 10) + \" \"",
-                "          + repeat(\"  \", that.indentLevel) + event.rule",
-                "      );",
-                "    }",
-                "  }",
-                "",
-                "  switch (event.type) {",
-                "    case \"rule.enter\":",
-                "      log(event);",
-                "      this.indentLevel++;",
-                "      break;",
-                "",
-                "    case \"rule.match\":",
-                "      this.indentLevel--;",
-                "      log(event);",
-                "      break;",
-                "",
-                "    case \"rule.fail\":",
-                "      this.indentLevel--;",
-                "      log(event);",
-                "      break;",
-                "",
-                "    // istanbul ignore next",
-                "    default:",
-                "      throw new Error(\"Invalid event type: \" + event.type + \".\");",
-                "  }",
-                "};",
-                ""
-            ].join( "\n" ) );
+            if ( use( "DefaultTracer" ) )
+
+                parts.push( [
+                    "function peg$DefaultTracer() {",
+                    "  this.indentLevel = 0;",
+                    "}",
+                    "",
+                    "peg$DefaultTracer.prototype.trace = function(event) {",
+                    "  var that = this;",
+                    "",
+                    "  function log(event) {",
+                    "    function repeat(string, n) {",
+                    "       var result = \"\", i;",
+                    "",
+                    "       for (i = 0; i < n; i++) {",
+                    "         result += string;",
+                    "       }",
+                    "",
+                    "       return result;",
+                    "    }",
+                    "",
+                    "    function pad(string, length) {",
+                    "      return string + repeat(\" \", length - string.length);",
+                    "    }",
+                    "",
+                    "    if (typeof console === \"object\") {",   // IE 8-10
+                    "      console.log(",
+                    "        event.location.start.line + \":\" + event.location.start.column + \"-\"",
+                    "          + event.location.end.line + \":\" + event.location.end.column + \" \"",
+                    "          + pad(event.type, 10) + \" \"",
+                    "          + repeat(\"  \", that.indentLevel) + event.rule",
+                    "      );",
+                    "    }",
+                    "  }",
+                    "",
+                    "  switch (event.type) {",
+                    "    case \"rule.enter\":",
+                    "      log(event);",
+                    "      this.indentLevel++;",
+                    "      break;",
+                    "",
+                    "    case \"rule.match\":",
+                    "      this.indentLevel--;",
+                    "      log(event);",
+                    "      break;",
+                    "",
+                    "    case \"rule.fail\":",
+                    "      this.indentLevel--;",
+                    "      log(event);",
+                    "      break;",
+                    "",
+                    "    // istanbul ignore next",
+                    "    default:",
+                    "      throw new Error(\"Invalid event type: \" + event.type + \".\");",
+                    "  }",
+                    "};",
+                    ""
+                ].join( "\n" ) );
+
+            else
+
+                parts.push( [
+                    "var peg$FauxTracer = {",
+                    "  trace: function(event) { }",
+                    "};",
+                    ""
+                ].join( "\n" ) );
 
         }
 
@@ -1257,10 +1268,19 @@ function generateJS( ast, session, options ) {
 
             }
 
-            parts.push( [
-                "  var peg$tracer = \"tracer\" in options ? options.tracer : new peg$DefaultTracer();",
-                ""
-            ].join( "\n" ) );
+            if ( use( "DefaultTracer" ) )
+
+                parts.push( [
+                    "  var peg$tracer = \"tracer\" in options ? options.tracer : new peg$DefaultTracer();",
+                    ""
+                ].join( "\n" ) );
+
+            else
+
+                parts.push( [
+                    "  var peg$tracer = \"tracer\" in options ? options.tracer : peg$FauxTracer;",
+                    ""
+                ].join( "\n" ) );
 
         }
 
@@ -1595,7 +1615,7 @@ function generateJS( ast, session, options ) {
 
         function generateParserObject() {
 
-            return options.trace
+            return options.trace && use( "DefaultTracer" )
                 ? [
                     "{",
                     "  SyntaxError: peg$SyntaxError,",
@@ -1614,7 +1634,7 @@ function generateJS( ast, session, options ) {
 
         function generateParserExports() {
 
-            return options.trace
+            return options.trace && use( "DefaultTracer" )
                 ? [
                     "{",
                     "  peg$SyntaxError as SyntaxError,",

lib/typings/api.d.ts

@@ -408,6 +408,7 @@ declare namespace peg {
             expected: boolean;
             error: boolean;
             filename: boolean;
+            DefaultTracer: boolean;
 
         }