fix(eslint-plugin): [switch-exhaustiveness-check] add support for covering a missing property with undefined (typescript-eslint#10232)

ronami · auvred · web-flow · commit f83a5910569a · 2024-11-04T09:03:05.000-05:00
* don't report on the 'missing' undefined type if it's covered with an undefined type

* projectService: false

* projectService: false on valid test too

* Update packages/eslint-plugin/src/rules/switch-exhaustiveness-check.ts

Co-authored-by: auvred &lt;61150013+auvred@users.noreply.github.com&gt;

* add relevant test

---------

Co-authored-by: auvred &lt;61150013+auvred@users.noreply.github.com&gt;
diff --git a/packages/eslint-plugin/src/rules/switch-exhaustiveness-check.ts b/packages/eslint-plugin/src/rules/switch-exhaustiveness-check.ts
@@ -155,6 +155,15 @@ export default createRule<Options, MessageIds>({
             continue;
           }
 
+          // "missing", "optional" and "undefined" types are different runtime objects,
+          // but all of them have TypeFlags.Undefined type flag
+          if (
+            [...caseTypes].some(tsutils.isIntrinsicUndefinedType) &&
+            tsutils.isIntrinsicUndefinedType(intersectionPart)
+          ) {
+            continue;
+          }
+
           missingLiteralBranchTypes.push(intersectionPart);
         }
       }
diff --git a/packages/eslint-plugin/tests/rules/switch-exhaustiveness-check.test.ts b/packages/eslint-plugin/tests/rules/switch-exhaustiveness-check.test.ts
@@ -912,6 +912,48 @@ switch (value) {
         },
       ],
     },
+    {
+      code: `
+function foo(x: string[]) {
+  switch (x[0]) {
+    case 'hi':
+      break;
+    case undefined:
+      break;
+  }
+}
+      `,
+      languageOptions: {
+        parserOptions: {
+          project: './tsconfig.noUncheckedIndexedAccess.json',
+          projectService: false,
+          tsconfigRootDir: rootPath,
+        },
+      },
+    },
+    {
+      code: `
+function foo(x: string[], y: string | undefined) {
+  const a = x[0];
+  if (typeof a === 'string') {
+    return;
+  }
+  switch (y) {
+    case 'hi':
+      break;
+    case a:
+      break;
+  }
+}
+      `,
+      languageOptions: {
+        parserOptions: {
+          project: './tsconfig.noUncheckedIndexedAccess.json',
+          projectService: false,
+          tsconfigRootDir: rootPath,
+        },
+      },
+    },
   ],
   invalid: [
     {
@@ -2717,5 +2759,43 @@ switch (value) {
         },
       ],
     },
+    {
+      code: `
+function foo(x: string[]) {
+  switch (x[0]) {
+    case 'hi':
+      break;
+  }
+}
+      `,
+      errors: [
+        {
+          column: 11,
+          line: 3,
+          messageId: 'switchIsNotExhaustive',
+          suggestions: [
+            {
+              messageId: 'addMissingCases',
+              output: `
+function foo(x: string[]) {
+  switch (x[0]) {
+    case 'hi':
+      break;
+    case undefined: { throw new Error('Not implemented yet: undefined case') }
+  }
+}
+      `,
+            },
+          ],
+        },
+      ],
+      languageOptions: {
+        parserOptions: {
+          project: './tsconfig.noUncheckedIndexedAccess.json',
+          projectService: false,
+          tsconfigRootDir: rootPath,
+        },
+      },
+    },
   ],
 });

Original file line number	Diff line number	Diff line change
`@@ -155,6 +155,15 @@ export default createRule<Options, MessageIds>({`
`155`	`155`	`continue;`
`156`	`156`	`}`
`157`	`157`
	`158`	`+ // "missing", "optional" and "undefined" types are different runtime objects,`
	`159`	`+ // but all of them have TypeFlags.Undefined type flag`
	`160`	`+ if (`
	`161`	`+ [...caseTypes].some(tsutils.isIntrinsicUndefinedType) &&`
	`162`	`+ tsutils.isIntrinsicUndefinedType(intersectionPart)`
	`163`	`+ ) {`
	`164`	`+ continue;`
	`165`	`+ }`
	`166`	`+`
`158`	`167`	`missingLiteralBranchTypes.push(intersectionPart);`
`159`	`168`	`}`
`160`	`169`	`}`