util: display a present-but-undefined error cause

ljharb · ljharb · commit 29c7b481621d · 2021-12-19T15:32:46.000-08:00
See #41097 (comment)
diff --git a/lib/internal/util/inspect.js b/lib/internal/util/inspect.js
@@ -1282,7 +1282,7 @@ function formatError(err, constructor, tag, ctx, keys) {
 
   removeDuplicateErrorKeys(ctx, keys, err, stack);
 
-  if (err.cause !== undefined &&
+  if ('cause' in err &&
       (keys.length === 0 || !keys.includes('cause'))) {
     keys.push('cause');
   }
diff --git a/test/message/util-inspect-error-cause.js b/test/message/util-inspect-error-cause.js
@@ -22,6 +22,9 @@ const cause5 = new Error('Object cause', {
            '    at Module._compile (node:internal/modules/cjs/loader:827:30)'
   }
 });
+const cause6 = new Error('undefined cause', {
+  cause: undefined
+});
 
 console.log(cause4);
 console.log(cause5);
diff --git a/test/message/util-inspect-error-cause.out b/test/message/util-inspect-error-cause.out
@@ -23,6 +23,17 @@ Error: Object cause
       '    at Module._compile (node:internal/modules/cjs/loader:827:30)'
   }
 }
+Error: undefined cause
+    at *
+    at *
+    at *
+    at *
+    at *
+    at *
+    at * {
+  [cause]: undefined
+  }
+}
 RangeError: New Stack Frames
     at *
 *[90m    at *[39m {
diff --git a/test/parallel/test-util-inspect.js b/test/parallel/test-util-inspect.js
@@ -665,9 +665,12 @@ assert.strictEqual(util.inspect(-5e-324), '-5e-324');
   delete falsyCause1.stack;
   const falsyCause2 = new Error(undefined, { cause: null });
   falsyCause2.stack = '';
+  const undefinedCause = new Error('', { cause: undefined });
+  undefinedCause.stack = '';
 
   assert.strictEqual(util.inspect(falsyCause1), '[Error] { [cause]: false }');
   assert.strictEqual(util.inspect(falsyCause2), '[Error] { [cause]: null }');
+  assert.strictEqual(util.inspect(undefinedCause), '[Error] { [cause]: undefined }');
 }
 
 {

Original file line number	Diff line number	Diff line change
`@@ -1282,7 +1282,7 @@ function formatError(err, constructor, tag, ctx, keys) {`
`1282`	`1282`
`1283`	`1283`	`removeDuplicateErrorKeys(ctx, keys, err, stack);`
`1284`	`1284`
`1285`		`- if (err.cause !== undefined &&`
	`1285`	`+ if ('cause' in err &&`
`1286`	`1286`	`(keys.length === 0 \|\| !keys.includes('cause'))) {`
`1287`	`1287`	`keys.push('cause');`
`1288`	`1288`	`}`
Original file line number	Diff line number	Diff line change
`@@ -22,6 +22,9 @@ const cause5 = new Error('Object cause', {`
`22`	`22`	`' at Module._compile (node:internal/modules/cjs/loader:827:30)'`
`23`	`23`	`}`
`24`	`24`	`});`
	`25`	`+const cause6 = new Error('undefined cause', {`
	`26`	`+ cause: undefined`
	`27`	`+});`
`25`	`28`
`26`	`29`	`console.log(cause4);`
`27`	`30`	`console.log(cause5);`
Original file line number	Diff line number	Diff line change
`@@ -665,9 +665,12 @@ assert.strictEqual(util.inspect(-5e-324), '-5e-324');`
`665`	`665`	`delete falsyCause1.stack;`
`666`	`666`	`const falsyCause2 = new Error(undefined, { cause: null });`
`667`	`667`	`falsyCause2.stack = '';`
	`668`	`+ const undefinedCause = new Error('', { cause: undefined });`
	`669`	`+ undefinedCause.stack = '';`
`668`	`670`
`669`	`671`	`assert.strictEqual(util.inspect(falsyCause1), '[Error] { [cause]: false }');`
`670`	`672`	`assert.strictEqual(util.inspect(falsyCause2), '[Error] { [cause]: null }');`
	`673`	`+ assert.strictEqual(util.inspect(undefinedCause), '[Error] { [cause]: undefined }');`
`671`	`674`	`}`
`672`	`675`
`673`	`676`	`{`