feat(linter): add typescript/no-generated-empty-object-type (#26958)

Adds `typescript/no-generated-empty-object-type` as a suspicious type-aware rule, reporting type operations such as `Pick<Data, never>` that resolve to `{}`. Type analysis stays in TSGolint; the rule has no options, fixes, or suggestions.

Requires a backend containing https://github.com/oxc-project/tsgolint/pull/1229. The shared type-aware snapshots were validated against a local build of that implementation. This PR leaves the pinned backend package unchanged.

apps/oxlint/fixtures/cli/tsgolint/.oxlintrc.json

@@ -14,6 +14,7 @@
     "typescript/no-duplicate-type-constituents": "error",
     "typescript/no-floating-promises": "error",
     "typescript/no-for-in-array": "error",
+    "typescript/no-generated-empty-object-type": "error",
     "typescript/no-implied-eval": "error",
     "typescript/no-meaningless-void-operator": "error",
     "typescript/no-misused-spread": "error",

apps/oxlint/fixtures/cli/tsgolint/no-generated-empty-object-type.ts

@@ -0,0 +1,15 @@
+type Data = { name: string; value: number };
+// These operations resolve to the empty object type.
+type EmptyOmit = Omit<Data, "name" | "value">;
+type EmptyPick = Pick<Data, never>;
+type EmptyNonNullable = NonNullable<unknown>;
+type EmptyIntersection = Omit<Data, "name" | "value"> & Omit<Data, "name" | "value">;
+// These operations retain properties.
+type WithValue = Omit<Data, "name">;
+type WithOther = Omit<Data, "name" | "value"> & { other: string };
+
+type Keys<T> = T extends infer U ? keyof U : never;
+type Mapped<T extends object> = { [Key in Keys<T>]: Key };
+type Referenced<T extends object> = Mapped<T>;
+
+export {};

apps/oxlint/src-js/package/config.generated.ts

@@ -1457,6 +1457,7 @@ export interface DummyRuleMap {
   "typescript/no-extraneous-class"?: RuleNoConfig | [AllowWarnDeny, NoExtraneousClass];
   "typescript/no-floating-promises"?: RuleNoConfig | [AllowWarnDeny, NoFloatingPromisesConfig];
   "typescript/no-for-in-array"?: RuleNoConfig;
+  "typescript/no-generated-empty-object-type"?: RuleNoConfig;
   "typescript/no-implied-eval"?: RuleNoConfig;
   "typescript/no-import-type-side-effects"?: RuleNoConfig;
   "typescript/no-inferrable-types"?: RuleNoConfig | [AllowWarnDeny, NoInferrableTypes];

apps/oxlint/src/snapshots/fixtures__cli__tsgolint_--type-aware --silent@oxlint.snap

@@ -6,8 +6,8 @@ arguments: --type-aware --silent
 working directory: fixtures/cli/tsgolint
 ----------
 
-Found 0 warnings and 81 errors.
-Finished in <variable>ms on 60 files with 59 rules using 1 threads.
+Found 0 warnings and 86 errors.
+Finished in <variable>ms on 61 files with 60 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------

apps/oxlint/src/snapshots/fixtures__cli__tsgolint_--type-aware -c config-test.json@oxlint.snap

@@ -42,7 +42,7 @@ working directory: fixtures/cli/tsgolint
   help: Remove the debugger statement
 
 Found 2 warnings and 2 errors.
-Finished in <variable>ms on 60 files with 2 rules using 1 threads.
+Finished in <variable>ms on 61 files with 2 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------

apps/oxlint/src/snapshots/fixtures__cli__tsgolint_--type-aware test.svelte@oxlint.snap

@@ -16,7 +16,7 @@ working directory: fixtures/cli/tsgolint
   help: Remove the debugger statement
 
 Found 0 warnings and 1 error.
-Finished in <variable>ms on 1 file with 59 rules using 1 threads.
+Finished in <variable>ms on 1 file with 60 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------

apps/oxlint/src/snapshots/fixtures__cli__tsgolint_--type-aware@oxlint.snap

@@ -113,6 +113,47 @@ working directory: fixtures/cli/tsgolint
    `----
   help: Use a more robust iteration method such as for-of or array.forEach instead.
 
+  x typescript(no-generated-empty-object-type): This type resolves to `{}`, the empty object type. This was likely not intentional.
+   ,-[no-generated-empty-object-type.ts:3:18]
+ 2 | // These operations resolve to the empty object type.
+ 3 | type EmptyOmit = Omit<Data, "name" | "value">;
+   :                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ 4 | type EmptyPick = Pick<Data, never>;
+   `----
+
+  x typescript(no-generated-empty-object-type): This type resolves to `{}`, the empty object type. This was likely not intentional.
+   ,-[no-generated-empty-object-type.ts:4:18]
+ 3 | type EmptyOmit = Omit<Data, "name" | "value">;
+ 4 | type EmptyPick = Pick<Data, never>;
+   :                  ^^^^^^^^^^^^^^^^^
+ 5 | type EmptyNonNullable = NonNullable<unknown>;
+   `----
+
+  x typescript(no-generated-empty-object-type): This type resolves to `{}`, the empty object type. This was likely not intentional.
+   ,-[no-generated-empty-object-type.ts:5:25]
+ 4 | type EmptyPick = Pick<Data, never>;
+ 5 | type EmptyNonNullable = NonNullable<unknown>;
+   :                         ^^^^^^^^^^^^^^^^^^^^
+ 6 | type EmptyIntersection = Omit<Data, "name" | "value"> & Omit<Data, "name" | "value">;
+   `----
+
+  x typescript(no-duplicate-type-constituents): Intersection type constituent is duplicated with  Omit<Data, "name" | "value">.
+   ,-[no-generated-empty-object-type.ts:6:57]
+ 5 | type EmptyNonNullable = NonNullable<unknown>;
+ 6 | type EmptyIntersection = Omit<Data, "name" | "value"> & Omit<Data, "name" | "value">;
+   :                          ^^^^^^^^^^^^^^|^^^^^^^^^^^^^   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   :                                        `-- Type 'Omit<Data, "name" | "value">' is first declared here.
+ 7 | // These operations retain properties.
+   `----
+
+  x typescript(no-generated-empty-object-type): This type resolves to `{}`, the empty object type. This was likely not intentional.
+   ,-[no-generated-empty-object-type.ts:6:26]
+ 5 | type EmptyNonNullable = NonNullable<unknown>;
+ 6 | type EmptyIntersection = Omit<Data, "name" | "value"> & Omit<Data, "name" | "value">;
+   :                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ 7 | // These operations retain properties.
+   `----
+
   x typescript(no-implied-eval): Implied eval.
    ,-[no-implied-eval.ts:1:12]
  1 | setTimeout('alert("Hi!");', 100);
@@ -694,8 +735,8 @@ working directory: fixtures/cli/tsgolint
    `----
   help: If your function does not access `this`, you can annotate it with `this: void`, or consider using an arrow function instead.
 
-Found 0 warnings and 81 errors.
-Finished in <variable>ms on 60 files with 59 rules using 1 threads.
+Found 0 warnings and 86 errors.
+Finished in <variable>ms on 61 files with 60 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------

apps/oxlint/src/snapshots/fixtures__cli__tsgolint_-c config-type-aware.json@oxlint.snap

@@ -42,7 +42,7 @@ working directory: fixtures/cli/tsgolint
   help: Remove the debugger statement
 
 Found 2 warnings and 2 errors.
-Finished in <variable>ms on 60 files with 2 rules using 1 threads.
+Finished in <variable>ms on 61 files with 2 rules using 1 threads.
 ----------
 CLI result: LintFoundErrors
 ----------

crates/oxc_linter/src/generated/rule_runner_impls.rs

@@ -1748,6 +1748,13 @@ impl RuleRunner for crate::rules::typescript::no_for_in_array::NoForInArray {
     const RUN_FUNCTIONS: RuleRunFunctionsImplemented = RuleRunFunctionsImplemented::Unknown;
 }
 
+impl RuleRunner
+    for crate::rules::typescript::no_generated_empty_object_type::NoGeneratedEmptyObjectType
+{
+    const NODE_TYPES: Option<&AstTypesBitset> = None;
+    const RUN_FUNCTIONS: RuleRunFunctionsImplemented = RuleRunFunctionsImplemented::Unknown;
+}
+
 impl RuleRunner for crate::rules::typescript::no_implied_eval::NoImpliedEval {
     const NODE_TYPES: Option<&AstTypesBitset> = None;
     const RUN_FUNCTIONS: RuleRunFunctionsImplemented = RuleRunFunctionsImplemented::Unknown;

crates/oxc_linter/src/rules.rs

@@ -267,6 +267,7 @@ pub(crate) mod typescript {
     pub mod no_extraneous_class;
     pub mod no_floating_promises;
     pub mod no_for_in_array;
+    pub mod no_generated_empty_object_type;
     pub mod no_implied_eval;
     pub mod no_import_type_side_effects;
     pub mod no_inferrable_types;

crates/oxc_linter/src/rules/typescript/no_generated_empty_object_type.rs

@@ -0,0 +1,51 @@
+use oxc_macros::declare_oxc_lint;
+
+use crate::rule::Rule;
+
+#[derive(Debug, Default, Clone)]
+pub struct NoGeneratedEmptyObjectType;
+
+declare_oxc_lint!(
+    /// ### What it does
+    ///
+    /// Disallows type operations that resolve to the empty object type `{}`.
+    /// This includes generic type references and intersections, but excludes
+    /// mapped types whose keys have not yet been resolved.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// The empty object type `{}` accepts any non-nullish value, including
+    /// primitives such as strings and numbers. Accidentally producing this type
+    /// with a utility type can therefore allow values that were not intended.
+    ///
+    /// This rule checks generated types. Use `typescript/no-empty-object-type`
+    /// to disallow explicitly written empty object types.
+    ///
+    /// ### Examples
+    ///
+    /// Examples of **incorrect** code for this rule:
+    /// ```ts
+    /// type Data = { name: string; value: number };
+    /// type Empty = Omit<Data, 'name' | 'value'>;
+    /// type NoProperties = Pick<Data, never>;
+    /// type NonNullish = NonNullable<unknown>;
+    /// ```
+    ///
+    /// Examples of **correct** code for this rule:
+    /// ```ts
+    /// type Data = { name: string; value: number };
+    /// type WithValue = Omit<Data, 'name'>;
+    /// type WithOther = Omit<Data, 'name' | 'value'> & { other: string };
+    ///
+    /// type Keys<T> = T extends infer U ? keyof U : never;
+    /// type Mapped<T extends object> = { [Key in Keys<T>]: Key };
+    /// type Referenced<T extends object> = Mapped<T>;
+    /// ```
+    NoGeneratedEmptyObjectType(tsgolint),
+    typescript,
+    suspicious,
+    version = "next",
+    short_description = "Disallow type operations that resolve to the empty object type.",
+);
+
+impl Rule for NoGeneratedEmptyObjectType {}

npm/oxlint/configuration_schema.json

@@ -8042,6 +8042,9 @@
         "typescript/no-for-in-array": {
           "$ref": "#/definitions/RuleNoConfig"
         },
+        "typescript/no-generated-empty-object-type": {
+          "$ref": "#/definitions/RuleNoConfig"
+        },
         "typescript/no-implied-eval": {
           "$ref": "#/definitions/RuleNoConfig"
         },