feat(eslint,oxlint)!: enforce type imports with inline specifiers

eslint/__snapshots__/typescript-node.json

@@ -206,6 +206,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [2],
     "@typescript-eslint/consistent-type-definitions": [1, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -437,6 +444,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],
@@ -2107,6 +2115,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [2],
     "@typescript-eslint/consistent-type-definitions": [0, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -2338,6 +2353,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],
@@ -4010,6 +4026,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [0],
     "@typescript-eslint/consistent-type-definitions": [1, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -4241,6 +4264,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],

eslint/__snapshots__/typescript-react.json

@@ -514,6 +514,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [2],
     "@typescript-eslint/consistent-type-definitions": [1, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -745,6 +752,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],
@@ -2656,6 +2664,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [2],
     "@typescript-eslint/consistent-type-definitions": [1, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -2887,6 +2902,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],
@@ -4881,6 +4897,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [0],
     "@typescript-eslint/consistent-type-definitions": [1, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -5112,6 +5135,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],
@@ -7026,6 +7050,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [0],
     "@typescript-eslint/consistent-type-definitions": [1, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -7257,6 +7288,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],

eslint/__snapshots__/typescript.json

@@ -206,6 +206,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [2],
     "@typescript-eslint/consistent-type-definitions": [1, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -437,6 +444,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],
@@ -2107,6 +2115,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [2],
     "@typescript-eslint/consistent-type-definitions": [0, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -2338,6 +2353,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],
@@ -4010,6 +4026,13 @@
     "@typescript-eslint/consistent-indexed-object-style": [2],
     "@typescript-eslint/consistent-type-assertions": [0],
     "@typescript-eslint/consistent-type-definitions": [1, "type"],
+    "@typescript-eslint/consistent-type-imports": [
+      1,
+      {
+        "disallowTypeAnnotations": false,
+        "fixStyle": "inline-type-imports"
+      }
+    ],
     "@typescript-eslint/dot-notation": [
       2,
       {
@@ -4241,6 +4264,7 @@
     "@typescript-eslint/no-for-in-array": [2],
     "@typescript-eslint/no-generated-empty-object-type": [2],
     "@typescript-eslint/no-implied-eval": [2],
+    "@typescript-eslint/no-import-type-side-effects": [1],
     "@typescript-eslint/no-inferrable-types": [2],
     "@typescript-eslint/no-invalid-void-type": [2],
     "@typescript-eslint/no-meaningless-void-operator": [2],

eslint/presets/typescript.test/type-imports.ts

@@ -0,0 +1,16 @@
+// Should be an error: Channel is only used as a type
+// eslint-disable-next-line @typescript-eslint/consistent-type-imports
+import { Channel } from "./type-imports/channel.ts";
+// Types and values from the same module can be imported in one statement
+import { type Message, createMessage } from "./type-imports/message.ts";
+// Imports that only contain types should use a top-level `import type`
+import type { Recipient } from "./type-imports/recipient.ts";
+// Should be an error: with verbatimModuleSyntax this compiles to a side-effect import
+// eslint-disable-next-line @typescript-eslint/no-import-type-side-effects
+import { type Sender } from "./type-imports/sender.ts";
+
+export const send = (sender: Sender, recipient: Recipient, channel: Channel): Message =>
+  createMessage(`${sender.name} → ${recipient.name} via ${channel.name}`);
+
+// import() type annotations are allowed since they are always erased
+export type MessageModule = typeof import("./type-imports/message.ts");

eslint/presets/typescript.test/type-imports/channel.ts

@@ -0,0 +1,3 @@
+export type Channel = {
+  name: string;
+};

eslint/presets/typescript.test/type-imports/message.ts

@@ -0,0 +1,5 @@
+export type Message = {
+  text: string;
+};
+
+export const createMessage = (text: string): Message => ({ text });

eslint/presets/typescript.test/type-imports/recipient.ts

@@ -0,0 +1,3 @@
+export type Recipient = {
+  name: string;
+};

eslint/presets/typescript.test/type-imports/sender.ts

@@ -0,0 +1,3 @@
+export type Sender = {
+  name: string;
+};

eslint/rules/typescript.js

@@ -40,6 +40,16 @@ export const typescript =
           ],
           "@typescript-eslint/class-literal-property-style": "off", // https://typescript-eslint.io/rules/class-literal-property-style
           "@typescript-eslint/consistent-type-definitions": ["warn", "type"], // https://typescript-eslint.io/rules/consistent-type-definitions
+          // Inline type specifiers avoid a second import statement from the same module.
+          // Combined with no-import-type-side-effects, imports that only contain types
+          // still use `import type` so that they are fully erased under verbatimModuleSyntax.
+          // `import("a").A` type annotations are allowed since they are always erased
+          // and are commonly used in test mocks, e.g. `importOriginal<typeof import("a")>()`.
+          "@typescript-eslint/consistent-type-imports": [
+            // https://typescript-eslint.io/rules/consistent-type-imports
+            "warn",
+            { disallowTypeAnnotations: false, fixStyle: "inline-type-imports" },
+          ],
           "@typescript-eslint/explicit-member-accessibility": [
             // https://typescript-eslint.io/rules/explicit-member-accessibility
             "warn",
@@ -69,6 +79,9 @@ export const typescript =
           ],
           "@typescript-eslint/no-empty-function": "off", // https://typescript-eslint.io/rules/no-empty-function
           "@typescript-eslint/no-empty-interface": "off", // https://typescript-eslint.io/rules/no-empty-interface
+          // With verbatimModuleSyntax, `import { type A } from "a"` is compiled to `import "a"`
+          // which keeps the module (and its side-effects) in the bundle.
+          "@typescript-eslint/no-import-type-side-effects": "warn", // https://typescript-eslint.io/rules/no-import-type-side-effects
           // `any` is sometimes useful for small and abstract functions.
           // Should only be used in isolated parts of the codebase.
           // Appropriate usage can only be checked in a PR review.

oxlint/__snapshots__/typescript-node.json

@@ -223,6 +223,15 @@
     "typescript/class-literal-property-style": "allow",
     "typescript/consistent-return": "warn",
     "typescript/consistent-type-definitions": ["warn", ["type"]],
+    "typescript/consistent-type-imports": [
+      "warn",
+      [
+        {
+          "disallowTypeAnnotations": false,
+          "fixStyle": "inline-type-imports"
+        }
+      ]
+    ],
     "typescript/explicit-member-accessibility": [
       "warn",
       [
@@ -249,6 +258,7 @@
     "typescript/no-floating-promises": "warn",
     "typescript/no-for-in-array": "warn",
     "typescript/no-implied-eval": "warn",
+    "typescript/no-import-type-side-effects": "warn",
     "typescript/no-meaningless-void-operator": "warn",
     "typescript/no-misused-new": "warn",
     "typescript/no-misused-spread": "warn",
@@ -567,6 +577,15 @@
     "typescript/class-literal-property-style": "allow",
     "typescript/consistent-return": "warn",
     "typescript/consistent-type-definitions": "allow",
+    "typescript/consistent-type-imports": [
+      "warn",
+      [
+        {
+          "disallowTypeAnnotations": false,
+          "fixStyle": "inline-type-imports"
+        }
+      ]
+    ],
     "typescript/explicit-member-accessibility": [
       "warn",
       [
@@ -593,6 +612,7 @@
     "typescript/no-floating-promises": "warn",
     "typescript/no-for-in-array": "warn",
     "typescript/no-implied-eval": "warn",
+    "typescript/no-import-type-side-effects": "warn",
     "typescript/no-meaningless-void-operator": "warn",
     "typescript/no-misused-new": "warn",
     "typescript/no-misused-spread": "warn",
@@ -919,6 +939,15 @@
     "typescript/consistent-return": "warn",
     "typescript/consistent-type-assertions": "allow",
     "typescript/consistent-type-definitions": ["warn", ["type"]],
+    "typescript/consistent-type-imports": [
+      "warn",
+      [
+        {
+          "disallowTypeAnnotations": false,
+          "fixStyle": "inline-type-imports"
+        }
+      ]
+    ],
     "typescript/explicit-member-accessibility": [
       "warn",
       [
@@ -945,6 +974,7 @@
     "typescript/no-floating-promises": "warn",
     "typescript/no-for-in-array": "warn",
     "typescript/no-implied-eval": "warn",
+    "typescript/no-import-type-side-effects": "warn",
     "typescript/no-meaningless-void-operator": "warn",
     "typescript/no-misused-new": "warn",
     "typescript/no-misused-spread": "warn",