feat!: Allow ts paths aliases (#84)

Author: scagood

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

@@ -15,14 +15,14 @@ const visitImport = require("../util/visit-import")
  * @returns {string[]} File extensions.
  */
 function getExistingExtensions(filePath) {
-    const basename = path.basename(filePath, path.extname(filePath))
+    const directory = path.dirname(filePath)
+    const extension = path.extname(filePath)
+    const basename = path.basename(filePath, extension)
+
     try {
         return fs
-            .readdirSync(path.dirname(filePath))
-            .filter(
-                filename =>
-                    path.basename(filename, path.extname(filename)) === basename
-            )
+            .readdirSync(directory)
+            .filter(filename => filename.startsWith(`${basename}.`))
             .map(filename => path.extname(filename))
     } catch (_error) {
         return []
@@ -74,47 +74,56 @@ module.exports = {
             }
 
             // Get extension.
-            const originalExt = path.extname(name)
-            const existingExts = getExistingExtensions(filePath)
-            const ext = path.extname(filePath) || existingExts.join(" or ")
-            const style = overrideStyle[ext] || defaultStyle
+            const currentExt = path.extname(name)
+            const actualExt = path.extname(filePath)
+            const style = overrideStyle[actualExt] || defaultStyle
+
+            const expectedExt = mapTypescriptExtension(
+                context,
+                filePath,
+                actualExt
+            )
 
             // Verify.
-            if (style === "always" && ext !== originalExt) {
-                const fileExtensionToAdd = mapTypescriptExtension(
-                    context,
-                    filePath,
-                    ext
-                )
+            if (style === "always" && currentExt !== expectedExt) {
                 context.report({
                     node,
                     messageId: "requireExt",
-                    data: { ext: fileExtensionToAdd },
+                    data: { ext: expectedExt },
                     fix(fixer) {
-                        if (existingExts.length !== 1) {
-                            return null
-                        }
                         const index = node.range[1] - 1
                         return fixer.insertTextBeforeRange(
                             [index, index],
-                            fileExtensionToAdd
+                            expectedExt
                         )
                     },
                 })
-            } else if (style === "never" && ext === originalExt) {
+            }
+
+            if (
+                style === "never" &&
+                currentExt !== "" &&
+                expectedExt !== "" &&
+                currentExt === expectedExt
+            ) {
+                const otherExtensions = getExistingExtensions(filePath)
+
+                let fix = fixer => {
+                    const index = name.lastIndexOf(currentExt)
+                    const start = node.range[0] + 1 + index
+                    const end = start + currentExt.length
+                    return fixer.removeRange([start, end])
+                }
+
+                if (otherExtensions.length > 1) {
+                    fix = undefined
+                }
+
                 context.report({
                     node,
                     messageId: "forbidExt",
-                    data: { ext },
-                    fix(fixer) {
-                        if (existingExts.length !== 1) {
-                            return null
-                        }
-                        const index = name.lastIndexOf(ext)
-                        const start = node.range[0] + 1 + index
-                        const end = start + ext.length
-                        return fixer.removeRange([start, end])
-                    },
+                    data: { ext: currentExt },
+                    fix,
                 })
             }
         }

lib/util/check-existence.js

@@ -10,6 +10,21 @@ const getAllowModules = require("./get-allow-modules")
 const isTypescript = require("./is-typescript")
 const mapTypescriptExtension = require("../util/map-typescript-extension")
 
+/**
+ * Reports a missing file from ImportTarget
+ * @param {RuleContext} context - A context to report.
+ * @param {import('../util/import-target.js')} target - A list of target information to check.
+ * @returns {void}
+ */
+function markMissing(context, target) {
+    context.report({
+        node: target.node,
+        loc: target.node.loc,
+        messageId: "notFound",
+        data: target,
+    })
+}
+
 /**
  * Checks whether or not each requirement target exists.
  *
@@ -24,36 +39,43 @@ exports.checkExistence = function checkExistence(context, targets) {
     const allowed = new Set(getAllowModules(context))
 
     for (const target of targets) {
-        const missingModule =
+        if (
             target.moduleName != null &&
             !allowed.has(target.moduleName) &&
             target.filePath == null
+        ) {
+            markMissing(context, target)
+            continue
+        }
+
+        if (target.moduleName != null) {
+            continue
+        }
+
+        let missingFile =
+            target.filePath == null ? false : !exists(target.filePath)
 
-        let missingFile = target.moduleName == null && !exists(target.filePath)
         if (missingFile && isTypescript(context)) {
             const parsed = path.parse(target.filePath)
+            const pathWithoutExt = path.resolve(parsed.dir, parsed.name)
+
             const reversedExts = mapTypescriptExtension(
                 context,
                 target.filePath,
                 parsed.ext,
                 true
             )
             const reversedPaths = reversedExts.map(
-                reversedExt =>
-                    path.resolve(parsed.dir, parsed.name) + reversedExt
+                reversedExt => pathWithoutExt + reversedExt
             )
             missingFile = reversedPaths.every(
                 reversedPath =>
                     target.moduleName == null && !exists(reversedPath)
             )
         }
-        if (missingModule || missingFile) {
-            context.report({
-                node: target.node,
-                loc: target.node.loc,
-                messageId: "notFound",
-                data: target,
-            })
+
+        if (missingFile) {
+            markMissing(context, target)
         }
     }
 }

lib/util/get-try-extensions.js

@@ -4,7 +4,7 @@
  */
 "use strict"
 
-const DEFAULT_VALUE = Object.freeze([".js", ".json", ".node"])
+const DEFAULT_VALUE = Object.freeze([".js", ".json", ".node", ".mjs", ".cjs"])
 
 /**
  * Gets `tryExtensions` property from a given option object.

lib/util/get-tsconfig.js

@@ -17,7 +17,7 @@ function getTSConfig(filename) {
  * Attempts to get the ExtensionMap from the tsconfig of a given file.
  *
  * @param {string} filename - The path to the file we need to find the tsconfig.json of
- * @returns {import("get-tsconfig").TsConfigResult}
+ * @returns {import("get-tsconfig").TsConfigResult | null}
  */
 function getTSConfigForFile(filename) {
     return getTsconfig(filename, "tsconfig.json", fsCache)

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

@@ -32,9 +32,14 @@ const tsConfigMapping = {
  * @property {Record<string, string[]>} backward Convert from javascript to typescript
  */
 
+/**
+ * @param {Record<string, string>} typescriptExtensionMap A forward extension mapping
+ * @returns {ExtensionMap}
+ */
 function normalise(typescriptExtensionMap) {
     const forward = {}
     const backward = {}
+
     for (const [typescript, javascript] of typescriptExtensionMap) {
         forward[typescript] = javascript
         if (!typescript) {
@@ -43,6 +48,7 @@ function normalise(typescriptExtensionMap) {
         backward[javascript] ??= []
         backward[javascript].push(typescript)
     }
+
     return { forward, backward }
 }
 
@@ -109,7 +115,7 @@ function getFromTSConfigFromFile(filename) {
  * 8. This returns `PRESERVE_MAPPING`.
  *
  * @param {import("eslint").Rule.RuleContext} context - The rule context.
- * @returns {string[]} A list of extensions.
+ * @returns {ExtensionMap} A list of extensions.
  */
 module.exports = function getTypescriptExtensionMap(context) {
     return (