feat: Allow for "allowImportingTsExtensions" (#134)

lib/util/get-try-extensions.js

@@ -4,7 +4,26 @@
  */
 "use strict"
 
-const DEFAULT_VALUE = Object.freeze([".js", ".json", ".node", ".mjs", ".cjs"])
+const { getTSConfigForContext } = require("./get-tsconfig")
+const isTypescript = require("./is-typescript")
+
+const DEFAULT_JS_VALUE = Object.freeze([
+    ".js",
+    ".json",
+    ".node",
+    ".mjs",
+    ".cjs",
+])
+const DEFAULT_TS_VALUE = Object.freeze([
+    ".js",
+    ".ts",
+    ".mjs",
+    ".mts",
+    ".cjs",
+    ".cts",
+    ".json",
+    ".node",
+])
 
 /**
  * Gets `tryExtensions` property from a given option object.
@@ -13,7 +32,7 @@ const DEFAULT_VALUE = Object.freeze([".js", ".json", ".node", ".mjs", ".cjs"])
  * @returns {string[]|null} The `tryExtensions` value, or `null`.
  */
 function get(option) {
-    if (option && option.tryExtensions && Array.isArray(option.tryExtensions)) {
+    if (Array.isArray(option?.tryExtensions)) {
         return option.tryExtensions.map(String)
     }
     return null
@@ -24,19 +43,29 @@ function get(option) {
  *
  * 1. This checks `options` property, then returns it if exists.
  * 2. This checks `settings.n` | `settings.node` property, then returns it if exists.
- * 3. This returns `[".js", ".json", ".node"]`.
+ * 3. This returns `[".js", ".json", ".node", ".mjs", ".cjs"]`.
  *
  * @param {RuleContext} context - The rule context.
  * @returns {string[]} A list of extensions.
  */
 module.exports = function getTryExtensions(context, optionIndex = 0) {
-    return (
-        get(context.options && context.options[optionIndex]) ||
-        get(
-            context.settings && (context.settings.n || context.settings.node)
-        ) ||
-        DEFAULT_VALUE
-    )
+    const configured =
+        get(context.options?.[optionIndex]) ??
+        get(context.settings?.n) ??
+        get(context.settings?.node)
+
+    if (configured != null) {
+        return configured
+    }
+
+    if (isTypescript(context)) {
+        const tsconfig = getTSConfigForContext(context)
+        if (tsconfig?.config?.compilerOptions?.allowImportingTsExtensions) {
+            return DEFAULT_TS_VALUE
+        }
+    }
+
+    return DEFAULT_JS_VALUE
 }
 
 module.exports.schema = {

lib/util/get-tsconfig.js

@@ -23,9 +23,27 @@ function getTSConfigForFile(filename) {
     return getTsconfig(filename, "tsconfig.json", fsCache)
 }
 
+/**
+ * Attempts to get the ExtensionMap from the tsconfig of a given file.
+ *
+ * @param {import('eslint').Rule.RuleContext} context - The current eslint context
+ * @returns {import("get-tsconfig").TsConfigResult | null}
+ */
+function getTSConfigForContext(context) {
+    // TODO: remove context.get(PhysicalFilename|Filename) when dropping eslint < v10
+    const filename =
+        context.physicalFilename ??
+        context.getPhysicalFilename?.() ??
+        context.filename ??
+        context.getFilename?.()
+
+    return getTSConfigForFile(filename)
+}
+
 module.exports = {
     getTSConfig,
     getTSConfigForFile,
+    getTSConfigForContext,
 }
 
 module.exports.schema = { type: "string" }

lib/util/get-typescript-extension-map.js

@@ -1,6 +1,6 @@
 "use strict"
 
-const { getTSConfig, getTSConfigForFile } = require("./get-tsconfig")
+const { getTSConfig, getTSConfigForContext } = require("./get-tsconfig")
 
 const DEFAULT_MAPPING = normalise([
     ["", ".js"],
@@ -95,11 +95,11 @@ function get(option) {
 /**
  * Attempts to get the ExtensionMap from the tsconfig of a given file.
  *
- * @param {string} filename - The filename we're getting from
+ * @param {import('eslint').Rule.RuleContext} context - The current file context
  * @returns {ExtensionMap} The `typescriptExtensionMap` value, or `null`.
  */
-function getFromTSConfigFromFile(filename) {
-    return getMappingFromTSConfig(getTSConfigForFile(filename)?.config)
+function getFromTSConfigFromFile(context) {
+    return getMappingFromTSConfig(getTSConfigForContext(context)?.config)
 }
 
 /**
@@ -118,15 +118,10 @@ function getFromTSConfigFromFile(filename) {
  * @returns {ExtensionMap} A list of extensions.
  */
 module.exports = function getTypescriptExtensionMap(context) {
-    const filename =
-        context.physicalFilename ??
-        context.getPhysicalFilename?.() ??
-        context.filename ??
-        context.getFilename?.() // TODO: remove context.get(PhysicalFilename|Filename) when dropping eslint < v10
     return (
         get(context.options?.[0]) ||
         get(context.settings?.n ?? context.settings?.node) ||
-        getFromTSConfigFromFile(filename) ||
+        getFromTSConfigFromFile(context) ||
         PRESERVE_MAPPING
     )
 }

lib/util/import-target.js

@@ -11,7 +11,7 @@ const isBuiltin = require("is-builtin-module")
 const resolver = require("enhanced-resolve")
 
 const isTypescript = require("./is-typescript")
-const { getTSConfigForFile } = require("./get-tsconfig.js")
+const { getTSConfigForContext } = require("./get-tsconfig.js")
 const getTypescriptExtensionMap = require("./get-typescript-extension-map")
 
 function removeTrailWildcard(input) {
@@ -28,16 +28,7 @@ function removeTrailWildcard(input) {
  * @returns {import('enhanced-resolve').ResolveOptions['alias'] | undefined}
  */
 function getTSConfigAliases(context) {
-    const tsConfig = getTSConfigForFile(
-        // eslint ^8
-        context.physicalFilename ??
-            // eslint ^7.28 (deprecated ^8)
-            context.getPhysicalFilename?.() ??
-            // eslint ^8 (if physicalFilename undefined)
-            context.filename ??
-            // eslint ^7 (deprecated ^8)
-            context.getFilename?.()
-    )
+    const tsConfig = getTSConfigForContext(context)
 
     const paths = tsConfig?.config?.compilerOptions?.paths
 

tests/fixtures/file-extension-in-import/ts-allow-extension/tsconfig.json

@@ -0,0 +1,6 @@
+{
+    "compilerOptions": {
+        "noEmit": true,
+        "allowImportingTsExtensions": true
+    }
+}

tests/fixtures/no-missing/ts-allow-extension/tsconfig.json

@@ -0,0 +1,6 @@
+{
+    "compilerOptions": {
+        "noEmit": true,
+        "allowImportingTsExtensions": true
+    }
+}

tests/lib/rules/file-extension-in-import.js

@@ -193,6 +193,17 @@ new RuleTester({
             code: "require('./e.js');",
             settings: { node: { typescriptExtensionMap: tsReactExtensionMap } },
         },
+
+        {
+            filename: fixture("ts-allow-extension/test.ts"),
+            code: "require('./file.js');",
+            env: { node: true },
+        },
+        {
+            filename: fixture("ts-allow-extension/test.ts"),
+            code: "require('./file.ts');",
+            env: { node: true },
+        },
     ],
     invalid: [
         {

tests/lib/rules/no-missing-import.js

@@ -290,6 +290,17 @@ ruleTester.run("no-missing-import", rule, {
             env: { node: true },
         },
 
+        {
+            filename: fixture("ts-allow-extension/test.ts"),
+            code: "import './file.js';",
+            env: { node: true },
+        },
+        {
+            filename: fixture("ts-allow-extension/test.ts"),
+            code: "import './file.ts';",
+            env: { node: true },
+        },
+
         // import()
         ...(DynamicImportSupported
             ? [