cache source map data forever by default

package.json

@@ -1,7 +1,7 @@
 {
   "name": "source-map-support",
   "description": "Fixes stack traces for files with source maps",
-  "version": "0.2.0",
+  "version": "0.2.1",
   "main": "./source-map-support.js",
   "scripts": {
     "test": "node_modules/mocha/bin/mocha"

source-map-support.js

@@ -2,25 +2,42 @@ var SourceMapConsumer = require('source-map').SourceMapConsumer;
 var path = require('path');
 var fs = require('fs');
 
+// If true, the caches are reset before a stack trace formatting operation
+var emptyCacheBetweenOperations = false;
+
+// Maps a file path to a string containing the file contents
+var fileContentsCache = {};
+
+// Maps a file path to a source map for that file
+var sourceMapCache = {};
+
 function isInBrowser() {
   return typeof window !== 'undefined';
 }
 
 function retrieveFile(path) {
+  if (path in fileContentsCache) {
+    return fileContentsCache[path];
+  }
+
   // Use SJAX if we are in the browser
   if (isInBrowser()) {
     var xhr = new XMLHttpRequest();
     xhr.open('GET', path, false);
     xhr.send(null);
-    return xhr.readyState === 4 ? xhr.responseText : null;
+    var contents = xhr.readyState === 4 ? xhr.responseText : null;
   }
 
   // Otherwise, use the filesystem
-  try {
-    return fs.readFileSync(path, 'utf8');
-  } catch (e) {
-    return null;
+  else {
+    try {
+      var contents = fs.readFileSync(path, 'utf8');
+    } catch (e) {
+      var contents = null;
+    }
   }
+
+  return fileContentsCache[path] = contents;
 }
 
 // Support URLs relative to a directory, but be careful about a protocol prefix
@@ -66,13 +83,13 @@ var retrieveSourceMap = function (source) {
   };
 };
 
-var mapSourcePosition = exports.mapSourcePosition = function(cache, position) {
-  var sourceMap = cache[position.source];
+var mapSourcePosition = exports.mapSourcePosition = function(position) {
+  var sourceMap = sourceMapCache[position.source];
   if (!sourceMap) {
     // Call the (overrideable) retrieveSourceMap function to get the source map.
     var urlAndMap = retrieveSourceMap(position.source);
     if (urlAndMap) {
-      sourceMap = cache[position.source] = {
+      sourceMap = sourceMapCache[position.source] = {
         url: urlAndMap.url,
         map: new SourceMapConsumer(urlAndMap.map)
       };
@@ -102,11 +119,11 @@ var mapSourcePosition = exports.mapSourcePosition = function(cache, position) {
 
 // Parses code generated by FormatEvalOrigin(), a function inside V8:
 // https://code.google.com/p/v8/source/browse/trunk/src/messages.js
-function mapEvalOrigin(cache, origin) {
+function mapEvalOrigin(origin) {
   // Most eval() calls are in this format
   var match = /^eval at ([^(]+) \((.+):(\d+):(\d+)\)$/.exec(origin);
   if (match) {
-    var position = mapSourcePosition(cache, {
+    var position = mapSourcePosition({
       source: match[2],
       line: match[3],
       column: match[4]
@@ -118,20 +135,20 @@ function mapEvalOrigin(cache, origin) {
   // Parse nested eval() calls using recursion
   match = /^eval at ([^(]+) \((.+)\)$/.exec(origin);
   if (match) {
-    return 'eval at ' + match[1] + ' (' + mapEvalOrigin(cache, match[2]) + ')';
+    return 'eval at ' + match[1] + ' (' + mapEvalOrigin(match[2]) + ')';
   }
 
   // Make sure we still return useful information if we didn't find anything
   return origin;
 }
 
-function wrapCallSite(cache, frame) {
+function wrapCallSite(frame) {
   // Most call sites will return the source file from getFileName(), but code
   // passed to eval() ending in "//# sourceURL=..." will return the source file
   // from getScriptNameOrSourceURL() instead
   var source = frame.getFileName() || frame.getScriptNameOrSourceURL();
   if (source) {
-    var position = mapSourcePosition(cache, {
+    var position = mapSourcePosition({
       source: source,
       line: frame.getLineNumber(),
       column: frame.getColumnNumber()
@@ -148,7 +165,7 @@ function wrapCallSite(cache, frame) {
   // Code called using eval() needs special handling
   var origin = frame.isEval() && frame.getEvalOrigin();
   if (origin) {
-    origin = mapEvalOrigin(cache, origin);
+    origin = mapEvalOrigin(origin);
     return {
       __proto__: frame,
       getEvalOrigin: function() { return origin; }
@@ -162,12 +179,12 @@ function wrapCallSite(cache, frame) {
 // This function is part of the V8 stack trace API, for more info see:
 // http://code.google.com/p/v8/wiki/JavaScriptStackTraceApi
 function prepareStackTrace(error, stack) {
-  // Store source maps in a cache so we don't load them more than once when
-  // formatting a single stack trace (don't cache them forever though in case
-  // the files change on disk and the user wants to see the updated mapping)
-  var cache = {};
+  if (emptyCacheBetweenOperations) {
+    fileContentsCache = {};
+    sourceMapCache = {};
+  }
   return error + stack.map(function(frame) {
-    return '\n    at ' + wrapCallSite(cache, frame);
+    return '\n    at ' + wrapCallSite(frame);
   }).join('');
 }
 
@@ -179,8 +196,7 @@ function handleUncaughtExceptions(error) {
   }
   var match = /\n    at [^(]+ \((.*):(\d+):(\d+)\)/.exec(error.stack);
   if (match) {
-    var cache = {};
-    var position = mapSourcePosition(cache, {
+    var position = mapSourcePosition({
       source: match[1],
       line: match[2],
       column: match[3]
@@ -206,6 +222,8 @@ exports.install = function(options) {
   options = options || {};
   var installHandler = 'handleUncaughtExceptions' in options ?
     options.handleUncaughtExceptions : true;
+  emptyCacheBetweenOperations = 'emptyCacheBetweenOperations' in options ?
+    options.emptyCacheBetweenOperations : false;
 
   // Allow source maps to be found by methods other than reading the files
   // directly from disk.

test.js

@@ -1,4 +1,6 @@
-require('./source-map-support').install();
+require('./source-map-support').install({
+  emptyCacheBetweenOperations: true // Needed to be able to test for failure
+});
 
 var SourceMapGenerator = require('source-map').SourceMapGenerator;
 var child_process = require('child_process');