module: add API for interacting with source maps

PR-URL: https://github.com/nodejs/node/pull/31132
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

3 files changed, 71 insertions, 31 deletions

diff --git a/lib/internal/source_map/prepare_stack_trace.js b/lib/internal/source_map/prepare_stack_trace.js
index df559b2cdfe..037a8dc53e0 100644
--- a/lib/internal/source_map/prepare_stack_trace.js
+++ b/lib/internal/source_map/prepare_stack_trace.js
@@ -29,7 +29,6 @@ const prepareStackTrace = (globalThis, error, trace) => {
     maybeOverridePrepareStackTrace(globalThis, error, trace);
   if (globalOverride !== kNoOverride) return globalOverride;
 
-  const { SourceMap } = require('internal/source_map/source_map');
   const errorString = ErrorToString.call(error);
 
   if (trace.length === 0) {
@@ -39,16 +38,19 @@ const prepareStackTrace = (globalThis, error, trace) => {
     let str = i !== 0 ? '\n    at ' : '';
     str = `${str}${t}`;
     try {
-      const sourceMap = findSourceMap(t.getFileName(), error);
-      if (sourceMap && sourceMap.data) {
-        const sm = new SourceMap(sourceMap.data);
+      const sm = findSourceMap(t.getFileName(), error);
+      if (sm) {
         // Source Map V3 lines/columns use zero-based offsets whereas, in
         // stack traces, they start at 1/1.
-        const [, , url, line, col] =
-                   sm.findEntry(t.getLineNumber() - 1, t.getColumnNumber() - 1);
-        if (url && line !== undefined && col !== undefined) {
+        const {
+          originalLine,
+          originalColumn,
+          originalSource
+        } = sm.findEntry(t.getLineNumber() - 1, t.getColumnNumber() - 1);
+        if (originalSource && originalLine !== undefined &&
+            originalColumn !== undefined) {
           str +=
-            `\n        -> ${url.replace('file://', '')}:${line + 1}:${col + 1}`;
+`\n        -> ${originalSource.replace('file://', '')}:${originalLine + 1}:${originalColumn + 1}`;
         }
       }
     } catch (err) {
diff --git a/lib/internal/source_map/source_map.js b/lib/internal/source_map/source_map.js
index 9044521b6d6..32fe43ac8f6 100644
--- a/lib/internal/source_map/source_map.js
+++ b/lib/internal/source_map/source_map.js
@@ -66,6 +66,14 @@
 
 'use strict';
 
+const {
+  Array
+} = primordials;
+
+const {
+  ERR_INVALID_ARG_TYPE
+} = require('internal/errors').codes;
+
 let base64Map;
 
 const VLQ_BASE_SHIFT = 5;
@@ -112,6 +120,7 @@ class StringCharIterator {
  * @param {SourceMapV3} payload
  */
 class SourceMap {
+  #payload;
   #reverseMappingsBySourceURL = [];
   #mappings = [];
   #sources = {};
@@ -129,17 +138,25 @@ class SourceMap {
       for (let i = 0; i < base64Digits.length; ++i)
         base64Map[base64Digits[i]] = i;
     }
-    this.#parseMappingPayload(payload);
+    this.#payload = cloneSourceMapV3(payload);
+    this.#parseMappingPayload();
+  }
+
+  /**
+   * @return {Object} raw source map v3 payload.
+   */
+  get payload() {
+    return cloneSourceMapV3(this.#payload);
   }
 
   /**
    * @param {SourceMapV3} mappingPayload
    */
-  #parseMappingPayload = (mappingPayload) => {
-    if (mappingPayload.sections)
-      this.#parseSections(mappingPayload.sections);
+  #parseMappingPayload = () => {
+    if (this.#payload.sections)
+      this.#parseSections(this.#payload.sections);
     else
-      this.#parseMap(mappingPayload, 0, 0);
+      this.#parseMap(this.#payload, 0, 0);
   }
 
   /**
@@ -175,24 +192,18 @@ class SourceMap {
     const entry = this.#mappings[first];
     if (!first && entry && (lineNumber < entry[0] ||
         (lineNumber === entry[0] && columnNumber < entry[1]))) {
-      return null;
+      return {};
+    } else if (!entry) {
+      return {};
+    } else {
+      return {
+        generatedLine: entry[0],
+        generatedColumn: entry[1],
+        originalSource: entry[2],
+        originalLine: entry[3],
+        originalColumn: entry[4]
+      };
     }
-    return entry;
-  }
-
-  /**
-   * @param {string} sourceURL of the originating resource
-   * @param {number} lineNumber in the originating resource
-   * @return {Array}
-   */
-  findEntryReversed(sourceURL, lineNumber) {
-    const mappings = this.#reverseMappingsBySourceURL[sourceURL];
-    for (; lineNumber < mappings.length; ++lineNumber) {
-      const mapping = mappings[lineNumber];
-      if (mapping)
-        return mapping;
-    }
-    return this.#mappings[0];
   }
 
   /**
@@ -296,6 +307,23 @@ function decodeVLQ(stringCharIterator) {
   return negative ? -result : result;
 }
 
+/**
+ * @param {SourceMapV3} payload
+ * @return {SourceMapV3}
+ */
+function cloneSourceMapV3(payload) {
+  if (typeof payload !== 'object') {
+    throw new ERR_INVALID_ARG_TYPE('payload', ['Object'], payload);
+  }
+  payload = { ...payload };
+  for (const key in payload) {
+    if (payload.hasOwnProperty(key) && Array.isArray(payload[key])) {
+      payload[key] = payload[key].slice(0);
+    }
+  }
+  return payload;
+}
+
 module.exports = {
   SourceMap
 };
diff --git a/lib/internal/source_map/source_map_cache.js b/lib/internal/source_map/source_map_cache.js
index 593c2c8277f..b64af7eed6e 100644
--- a/lib/internal/source_map/source_map_cache.js
+++ b/lib/internal/source_map/source_map_cache.js
@@ -37,6 +37,7 @@ const cjsSourceMapCache = new WeakMap();
 const esmSourceMapCache = new Map();
 const { fileURLToPath, URL } = require('url');
 let Module;
+let SourceMap;
 
 let experimentalSourceMaps;
 function maybeCacheSourceMap(filename, content, cjsModuleInstance) {
@@ -222,8 +223,13 @@ function appendCJSCache(obj) {
 
 // Attempt to lookup a source map, which is either attached to a file URI, or
 // keyed on an error instance.
+// TODO(bcoe): once WeakRefs are available in Node.js, refactor to drop
+// requirement of error parameter.
 function findSourceMap(uri, error) {
   if (!Module) Module = require('internal/modules/cjs/loader').Module;
+  if (!SourceMap) {
+    SourceMap = require('internal/source_map/source_map').SourceMap;
+  }
   let sourceMap = cjsSourceMapCache.get(Module._cache[uri]);
   if (!uri.startsWith('file://')) uri = normalizeReferrerURL(uri);
   if (sourceMap === undefined) {
@@ -235,7 +241,11 @@ function findSourceMap(uri, error) {
       sourceMap = candidateSourceMap;
     }
   }
-  return sourceMap;
+  if (sourceMap && sourceMap.data) {
+    return new SourceMap(sourceMap.data);
+  } else {
+    return undefined;
+  }
 }
 
 module.exports = {