process: suggest --trace-warnings when printing warning

Suggest using `--trace-warnings` or `--trace-deprecation` the first
time a warning is emitted without a stack trace, similar to how
we suggest `--trace-uncaught` when printing uncaught exceptions
without a stack trace.

PR-URL: #32797
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: David Carlier <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>

Author: addaleax

lib/internal/process/warning.js

@@ -58,6 +58,7 @@ function doEmitWarning(warning) {
   return () => process.emit('warning', warning);
 }
 
+let traceWarningHelperShown = false;
 function onWarning(warning) {
   if (!(warning instanceof Error)) return;
   const isDeprecation = warning.name === 'DeprecationWarning';
@@ -78,6 +79,13 @@ function onWarning(warning) {
   if (typeof warning.detail === 'string') {
     msg += `\n${warning.detail}`;
   }
+  if (!trace && !traceWarningHelperShown) {
+    const flag = isDeprecation ? '--trace-deprecation' : '--trace-warnings';
+    const argv0 = require('path').basename(process.argv0 || 'node', '.exe');
+    msg += `\n(Use \`${argv0} ${flag} ...\` to show where the warning ` +
+           'was created)';
+    traceWarningHelperShown = true;
+  }
   const warningFile = lazyOption();
   if (warningFile) {
     return writeToFile(msg);

test/message/async_error_sync_esm.out

@@ -1,4 +1,5 @@
 (node:*) ExperimentalWarning: The ESM module loader is experimental.
+(Use `node --trace-warnings ...` to show where the warning was created)
 Error: test
     at one (*fixtures*async-error.js:4:9)
     at two (*fixtures*async-error.js:17:9)

test/message/esm_display_syntax_error.out

@@ -1,4 +1,5 @@
 (node:*) ExperimentalWarning: The ESM module loader is experimental.
+(Use `node --trace-warnings ...` to show where the warning was created)
 file:///*/test/message/esm_display_syntax_error.mjs:2
 await async () => 0;
 ^^^^^

test/message/esm_display_syntax_error_import.out

@@ -1,4 +1,5 @@
 (node:*) ExperimentalWarning: The ESM module loader is experimental.
+(Use `node --trace-warnings ...` to show where the warning was created)
 file:///*/test/message/esm_display_syntax_error_import.mjs:5
   notfound
   ^^^^^^^^

test/message/esm_display_syntax_error_import_module.out

@@ -1,4 +1,5 @@
 (node:*) ExperimentalWarning: The ESM module loader is experimental.
+(Use `node --trace-warnings ...` to show where the warning was created)
 file:///*/test/fixtures/es-module-loaders/syntax-error-import.mjs:1
 import { foo, notfound } from './module-named-exports.mjs';
               ^^^^^^^^

test/message/esm_display_syntax_error_module.out

@@ -1,7 +1,8 @@
 (node:*) ExperimentalWarning: The ESM module loader is experimental.
+(Use `node --trace-warnings ...` to show where the warning was created)
 file:///*/test/fixtures/es-module-loaders/syntax-error.mjs:2
 await async () => 0;
 ^^^^^
 
 SyntaxError: Unexpected reserved word
-    at Loader.moduleStrategy (internal/modules/esm/translators.js:*:*)
+    at Loader.moduleStrategy (internal/modules/esm/translators.js:*:*)

test/message/esm_loader_not_found.out

@@ -1,4 +1,5 @@
 (node:*) ExperimentalWarning: The ESM module loader is experimental.
+(Use `node --trace-warnings ...` to show where the warning was created)
 (node:*) ExperimentalWarning: --experimental-loader is an experimental feature. This feature could change at any time
 internal/modules/run_main.js:*
     internalBinding('errors').triggerUncaughtException(

test/message/esm_loader_syntax_error.out

@@ -1,4 +1,5 @@
 (node:*) ExperimentalWarning: The ESM module loader is experimental.
+(Use `node --trace-warnings ...` to show where the warning was created)
 (node:*) ExperimentalWarning: --experimental-loader is an experimental feature. This feature could change at any time
 file://*/test/fixtures/es-module-loaders/syntax-error.mjs:2
 await async () => 0;

test/message/v8_warning.out

@@ -1 +1,2 @@
 (node:*) V8: *v8_warning.js:* Invalid asm.js: Invalid return type
+(Use `node --trace-warnings ...` to show where the warning was created)

test/parallel/test-debugger-pid.js

@@ -29,9 +29,12 @@ interfacer.on('line', function(line) {
     case 1:
       expected =
         new RegExp(`^\\(node:${pid}\\) \\[DEP0068\\] DeprecationWarning: `);
-      assert.ok(expected.test(line), `expected regexp match for ${line}`);
+      assert.match(line, expected);
       break;
     case 2:
+      assert.match(line, /Use `node --trace-deprecation \.\.\.` to show where /);
+      break;
+    case 3:
       // Doesn't currently work on Windows.
       if (!common.isWindows) {
         expected = "Target process: 655555 doesn't exist.";
@@ -48,6 +51,6 @@ interfacer.on('line', function(line) {
 interfacer.on('exit', function(code, signal) {
   assert.strictEqual(code, 1, `Got unexpected code: ${code}`);
   if (!common.isWindows) {
-    assert.strictEqual(lineCount, 2);
+    assert.strictEqual(lineCount, 3);
   }
 });