util: highlight stack frames

Using `util.inspect` on errors is going to highlight userland and
node_module stack frames from now on. This is done by marking Node.js
core frames grey and frames that contain `node_modules` in their path
yellow.

That way it's easy to grasp what frames belong to what code.

PR-URL: https://github.com/nodejs/node/pull/27052
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/util.md

@@ -638,15 +638,16 @@ via the `util.inspect.styles` and `util.inspect.colors` properties.
 
 The default styles and associated colors are:
 
- * `number` - `yellow`
+* `number` - `yellow`
- * `boolean` - `yellow`
+* `boolean` - `yellow`
- * `string` - `green`
+* `string` - `green`
- * `date` - `magenta`
+* `date` - `magenta`
- * `regexp` - `red`
+* `module` - `underline`
- * `null` - `bold`
+* `regexp` - `red`
- * `undefined` - `grey`
+* `null` - `bold`
- * `special` - `cyan` (only applied to functions at this time)
+* `undefined` - `grey`
- * `name` - (no styling)
+* `special` - `cyan` (only applied to functions at this time)
+* `name` - (no styling)
 
 The predefined color codes are: `white`, `grey`, `black`, `blue`, `cyan`,
 `green`, `magenta`, `red` and `yellow`. There are also `bold`, `italic`,

lib/internal/util/inspect.js

@@ -86,6 +86,8 @@ const {
 
 const assert = require('internal/assert');
 
+const { NativeModule } = require('internal/bootstrap/loaders');
+
 let hexSlice;
 
 const inspectDefaultOptions = Object.seal({
@@ -115,6 +117,9 @@ const strEscapeSequencesReplacerSingle = /[\x00-\x1f\x5c]/g;
 const keyStrRegExp = /^[a-zA-Z_][a-zA-Z_0-9]*$/;
 const numberRegExp = /^(0|[1-9][0-9]*)$/;
 
+const coreModuleRegExp = /^    at (?:[^/\\(]+ \(|)((?<![/\\]).+)\.js:\d+:\d+\)?$/;
+const nodeModulesRegExp = /[/\\]node_modules[/\\](.+?)(?=[/\\])/g;
+
 const readableRegExps = {};
 
 const kMinLineLength = 16;
@@ -253,7 +258,8 @@ inspect.styles = Object.assign(Object.create(null), {
   symbol: 'green',
   date: 'magenta',
   // "name": intentionally not styling
-  regexp: 'red'
+  regexp: 'red',
+  module: 'underline'
 });
 
 function addQuotes(str, quotes) {
@@ -838,10 +844,37 @@ function formatError(err, constructor, tag, ctx) {
       }
     }
   }
+  // Ignore the error message if it's contained in the stack.
+  let pos = err.message && stack.indexOf(err.message) || -1;
+  if (pos !== -1)
+    pos += err.message.length;
   // Wrap the error in brackets in case it has no stack trace.
-  const stackStart = stack.indexOf('\n    at');
+  const stackStart = stack.indexOf('\n    at', pos);
   if (stackStart === -1) {
     stack = `[${stack}]`;
+  } else if (ctx.colors) {
+    // Highlight userland code and node modules.
+    let newStack = stack.slice(0, stackStart);
+    const lines = stack.slice(stackStart + 1).split('\n');
+    for (const line of lines) {
+      const core = line.match(coreModuleRegExp);
+      if (core !== null && NativeModule.exists(core[1])) {
+        newStack += `\n${ctx.stylize(line, 'undefined')}`;
+      } else {
+        // This adds underscores to all node_modules to quickly identify them.
+        let nodeModule;
+        newStack += '\n';
+        let pos = 0;
+        while (nodeModule = nodeModulesRegExp.exec(line)) {
+          // '/node_modules/'.length === 14
+          newStack += line.slice(pos, nodeModule.index + 14);
+          newStack += ctx.stylize(nodeModule[1], 'module');
+          pos = nodeModule.index + nodeModule[0].length;
+        }
+        newStack += pos === 0 ? line : line.slice(pos);
+      }
+    }
+    stack = newStack;
   }
   // The message and the stack have to be indented as well!
   if (ctx.indentationLvl !== 0) {

test/fixtures/node_modules/node_modules/bar.js

@@ -19,6 +19,4 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-console.error(__filename);
-console.error(module.paths.join('\n') + '\n');
 throw new Error('Should not ever get here.');

test/parallel/test-util-inspect.js

@@ -2311,3 +2311,43 @@ assert.strictEqual(
 
   assert.strictEqual(out, expected);
 }
+
+{
+  // Use a fake stack to verify the expected colored outcome.
+  const stack = [
+    'TypedError: Wonderful message!',
+    '    at A.<anonymous> (/test/node_modules/foo/node_modules/bar/baz.js:2:7)',
+    '    at Module._compile (internal/modules/cjs/loader.js:827:30)',
+    '    at Fancy (vm.js:697:32)',
+    // This file is not an actual Node.js core file.
+    '    at tryModuleLoad (internal/modules/cjs/foo.js:629:12)',
+    '    at Function.Module._load (internal/modules/cjs/loader.js:621:3)',
+    // This file is not an actual Node.js core file.
+    '    at Module.require [as weird/name] (internal/aaaaaa/loader.js:735:19)',
+    '    at require (internal/modules/cjs/helpers.js:14:16)',
+    '    at /test/test-util-inspect.js:2239:9',
+    '    at getActual (assert.js:592:5)'
+  ];
+  const isNodeCoreFile = [
+    false, false, true, true, false, true, false, true, false, true
+  ];
+  const err = new TypeError('Wonderful message!');
+  err.stack = stack.join('\n');
+  util.inspect(err, { colors: true }).split('\n').forEach((line, i) => {
+    let actual = stack[i].replace(/node_modules\/([a-z]+)/g, (a, m) => {
+      return `node_modules/\u001b[4m${m}\u001b[24m`;
+    });
+    if (isNodeCoreFile[i]) {
+      actual = `\u001b[90m${actual}\u001b[39m`;
+    }
+    assert.strictEqual(actual, line);
+  });
+}
+
+{
+  // Cross platform checks.
+  const err = new Error('foo');
+  util.inspect(err, { colors: true }).split('\n').forEach((line, i) => {
+    assert(i < 2 || line.startsWith('\u001b[90m'));
+  });
+}

test/pseudo-tty/console_colors.js

@@ -1,5 +1,6 @@
 'use strict';
 require('../common');
+const vm = require('vm');
 // Make this test OS-independent by overriding stdio getColorDepth().
 process.stdout.getColorDepth = () => 8;
 process.stderr.getColorDepth = () => 8;
@@ -7,3 +8,15 @@ process.stderr.getColorDepth = () => 8;
 console.log({ foo: 'bar' });
 console.log('%s q', 'string');
 console.log('%o with object format param', { foo: 'bar' });
+
+console.log(
+  new Error('test\n    at abc (../fixtures/node_modules/bar.js:4:4)\nfoobar')
+);
+
+try {
+  require('../fixtures/node_modules/node_modules/bar.js');
+} catch (err) {
+  console.log(err);
+}
+
+vm.runInThisContext('console.log(new Error())');

test/pseudo-tty/console_colors.out

@@ -1,3 +1,38 @@
 { foo: *[32m'bar'*[39m }
 string q
 { foo: *[32m'bar'*[39m } with object format param
+
+Error: test
+at abc (../fixtures/node_modules/bar.js:4:4)
+foobar
+at * (*console_colors.js:*:*)
+*[90m    at * (internal*:*:*)*[39m
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+
+Error: Should not ever get here.
+at * (*node_modules*[4m*node_modules*[24m*bar.js:*:*)
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+at * (*console_colors.js:*:*)
+*[90m    at *[39m
+*[90m    at *[39m
+
+Error
+at evalmachine.<anonymous>:*:*
+*[90m    at Script.runInThisContext (vm.js:*:*)*[39m
+*[90m    at Object.runInThisContext (vm.js:*:*)*[39m
+at * (*console_colors.js:*:*)
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m
+*[90m    at *[39m