Support tsconfig.json & jsconfig.json aliases (#1747)

* Resolve paths from tsconfig or jsconfig

https://code.visualstudio.com/docs/languages/jsconfig
https://nextjs.org/docs/advanced-features/module-path-aliases

* edit: rename plugin to `@astrojs/vite-plugin-tsconfig-alias`

Co-authored-by: Nate Moore <natemoo-re@users.noreply.github.com>

* edit: switch from `ps` to `path.posix`

* edit: move sanitization of paths to loop

* edit: rename `resolveConfigPaths` to `configAliasVitePlugin`

* edit: update implementation based on feedback

* prettier

* edit: rename `matchTailingAsterisk` to `matchTrailingAsterisk`

* edit: cleanup with comments

* edit: spellcheck `condition` to `conditionally`

* edit: refactor based on feedback

* edit: Update README.md

* edit: cleanup baseUrl transformation and add explainer comments

* edit: cleanup resolutions and add commenting

* yarn lint

Co-authored-by: Nate Moore <natemoo-re@users.noreply.github.com>

5 files changed, 154 insertions, 3 deletions

diff --git a/packages/astro/package.json b/packages/astro/package.json
index c43e6a9d5..a84b295e3 100644
--- a/packages/astro/package.json
+++ b/packages/astro/package.json
@@ -96,6 +96,7 @@
     "strip-indent": "^4.0.0",
     "supports-esm": "^1.0.0",
     "tiny-glob": "^0.2.8",
+    "tsconfig-resolver": "^3.0.1",
     "vite": "^2.6.10",
     "yargs-parser": "^20.2.9",
     "zod": "^3.8.1"
diff --git a/packages/astro/src/core/create-vite.ts b/packages/astro/src/core/create-vite.ts
index b49f664dc..c883333da 100644
--- a/packages/astro/src/core/create-vite.ts
+++ b/packages/astro/src/core/create-vite.ts
@@ -6,6 +6,7 @@ import { fileURLToPath } from 'url';
 import vite from './vite.js';
 import astroVitePlugin from '../vite-plugin-astro/index.js';
 import astroPostprocessVitePlugin from '../vite-plugin-astro-postprocess/index.js';
+import configAliasVitePlugin from '../vite-plugin-config-alias/index.js';
 import markdownVitePlugin from '../vite-plugin-markdown/index.js';
 import jsxVitePlugin from '../vite-plugin-jsx/index.js';
 import fetchVitePlugin from '../vite-plugin-fetch/index.js';
@@ -47,6 +48,7 @@ export async function createVite(inlineConfig: ViteConfigWithSSR, { astroConfig,
       entries: ['src/**/*'], // Try and scan a user’s project (won’t catch everything),
     },
     plugins: [
+      configAliasVitePlugin({ config: astroConfig }),
       astroVitePlugin({ config: astroConfig, devServer }),
       markdownVitePlugin({ config: astroConfig, devServer }),
       jsxVitePlugin({ config: astroConfig, logging }),
diff --git a/packages/astro/src/vite-plugin-config-alias/README.md b/packages/astro/src/vite-plugin-config-alias/README.md
new file mode 100644
index 000000000..85971c90a
--- /dev/null
+++ b/packages/astro/src/vite-plugin-config-alias/README.md
@@ -0,0 +1,26 @@
+# vite-plugin-config-alias
+
+This adds aliasing support to Vite from `tsconfig.json` or `jsconfig.json` files.
+
+Consider the following example configuration:
+
+```
+{
+  "compilerOptions": {
+    "baseUrl": "src",
+    "paths": {
+      "components:*": ["components/*.astro"]
+    }
+  }
+}
+```
+
+With this configuration, the following imports would map to the same location.
+
+```js
+import Test from '../components/Test.astro'
+
+import Test from 'components/Test.astro'
+
+import Test from 'components:Test'
+```
diff --git a/packages/astro/src/vite-plugin-config-alias/index.ts b/packages/astro/src/vite-plugin-config-alias/index.ts
new file mode 100644
index 000000000..8154730f4
--- /dev/null
+++ b/packages/astro/src/vite-plugin-config-alias/index.ts
@@ -0,0 +1,105 @@
+import * as tsr from 'tsconfig-resolver';
+import * as path from 'path';
+import * as url from 'url';
+
+import type * as vite from 'vite';
+
+/** Result of successfully parsed tsconfig.json or jsconfig.json. */
+export declare interface Alias {
+  find: RegExp;
+  replacement: string;
+}
+
+/** Returns a path with its slashes replaced with posix slashes. */
+const normalize = (pathname: string) => String(pathname).split(path.sep).join(path.posix.sep);
+
+/** Returns the results of a config file if it exists, otherwise null. */
+const getExistingConfig = (searchName: string, cwd: string | undefined): tsr.TsConfigResultSuccess | null => {
+  const config = tsr.tsconfigResolverSync({ cwd, searchName });
+
+  return config.exists ? config : null;
+};
+
+/** Returns a list of compiled aliases. */
+const getConfigAlias = (cwd: string | undefined): Alias[] | null => {
+  /** Closest tsconfig.json or jsconfig.json */
+  const config = getExistingConfig('tsconfig.json', cwd) || getExistingConfig('jsconfig.json', cwd);
+
+  // if no config was found, return null
+  if (!config) return null;
+
+  /** Compiler options from tsconfig.json or jsconfig.json. */
+  const compilerOptions = Object(config.config.compilerOptions);
+
+  // if no compilerOptions.baseUrl was defined, return null
+  if (!compilerOptions.baseUrl) return null;
+
+  // resolve the base url from the configuration file directory
+  const baseUrl = path.posix.resolve(path.posix.dirname(normalize(config.path)), normalize(compilerOptions.baseUrl));
+
+  /** List of compiled alias expressions. */
+  const aliases: Alias[] = [];
+
+  // compile any alias expressions and push them to the list
+  for (let [alias, values] of Object.entries(Object(compilerOptions.paths) as { [key: string]: string[] })) {
+    values = [].concat(values as never);
+
+    /** Regular Expression used to match a given path. */
+    const find = new RegExp(`^${[...alias].map((segment) => (segment === '*' ? '(.+)' : segment.replace(/[\\^$*+?.()|[\]{}]/, '\\$&'))).join('')}$`);
+
+    /** Internal index used to calculate the matching id in a replacement. */
+    let matchId = 0;
+
+    for (let value of values) {
+      /** String used to replace a matched path. */
+      const replacement = [...path.posix.resolve(baseUrl, value)].map((segment) => (segment === '*' ? `$${++matchId}` : segment === '$' ? '$$' : segment)).join('');
+
+      aliases.push({ find, replacement });
+    }
+  }
+
+  // compile the baseUrl expression and push it to the list
+  // - `baseUrl` changes the way non-relative specifiers are resolved
+  // - if `baseUrl` exists then all non-relative specifiers are resolved relative to it
+  aliases.push({
+    find: /^(?!\.*\/)(.+)$/,
+    replacement: `${[...baseUrl].map((segment) => (segment === '$' ? '$$' : segment)).join('')}/$1`,
+  });
+
+  return aliases;
+};
+
+/** Returns a Vite plugin used to alias pathes from tsconfig.json and jsconfig.json. */
+export default function configAliasVitePlugin(astroConfig: { projectRoot?: URL; [key: string]: unknown }): vite.PluginOption {
+  /** Aliases from the tsconfig.json or jsconfig.json configuration. */
+  const configAlias = getConfigAlias(astroConfig.projectRoot && url.fileURLToPath(astroConfig.projectRoot));
+
+  // if no config alias was found, bypass this plugin
+  if (!configAlias) return {} as vite.PluginOption;
+
+  return {
+    name: '@astrojs/vite-plugin-config-alias',
+    enforce: 'pre',
+    async resolveId(sourceId: string, importer, options) {
+      /** Resolved ID conditionally handled by any other resolver. (this gives priority to all other resolvers) */
+      const resolvedId = await this.resolve(sourceId, importer, { skipSelf: true, ...options });
+
+      // if any other resolver handles the file, return that resolution
+      if (resolvedId) return resolvedId;
+
+      // conditionally resolve the source ID from any matching alias or baseUrl
+      for (const alias of configAlias) {
+        if (alias.find.test(sourceId)) {
+          /** Processed Source ID with our alias applied. */
+          const aliasedSourceId = sourceId.replace(alias.find, alias.replacement);
+
+          /** Resolved ID conditionally handled by any other resolver. (this also gives priority to all other resolvers) */
+          const resolvedAliasedId = await this.resolve(aliasedSourceId, importer, { skipSelf: true, ...options });
+
+          // if the existing resolvers find the file, return that resolution
+          if (resolvedAliasedId) return resolvedAliasedId;
+        }
+      }
+    },
+  };
+}
diff --git a/yarn.lock b/yarn.lock
index 5de4d7366..e0d2acfd9 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1898,6 +1898,11 @@
   resolved "https://registry.yarnpkg.com/@types/json-schema/-/json-schema-7.0.9.tgz#97edc9037ea0c38585320b28964dde3b39e4660d"
   integrity sha512-qcUXuemtEu+E5wZSJHNxUXeCZhAfXKQ41D+duX+VYPde7xyEVZci+/oXKJL13tnRs9lR2pr4fod59GT6/X1/yQ==
 
+"@types/json5@^0.0.30":
+  version "0.0.30"
+  resolved "https://registry.yarnpkg.com/@types/json5/-/json5-0.0.30.tgz#44cb52f32a809734ca562e685c6473b5754a7818"
+  integrity sha512-sqm9g7mHlPY/43fcSNrCYfOeX9zkTTK+euO5E6+CVijSMm5tTjkVdwdqRkY3ljjIAf8679vps5jKUoJBCLsMDA==
+
 "@types/mdast@^3.0.0", "@types/mdast@^3.0.3":
   version "3.0.10"
   resolved "https://registry.yarnpkg.com/@types/mdast/-/mdast-3.0.10.tgz#4724244a82a4598884cbbe9bcfd73dff927ee8af"
@@ -1990,7 +1995,7 @@
   dependencies:
     "@types/node" "*"
 
-"@types/resolve@^1.20.1":
+"@types/resolve@^1.17.0", "@types/resolve@^1.20.1":
   version "1.20.1"
   resolved "https://registry.yarnpkg.com/@types/resolve/-/resolve-1.20.1.tgz#3727e48042fda81e374f5d5cf2fa92288bf698f8"
   integrity sha512-Ku5+GPFa12S3W26Uwtw+xyrtIpaZsGYHH6zxNbZlstmlvMYSZRzOwzwsXbxlVUbHyUucctSyuFtu6bNxwYomIw==
@@ -6458,7 +6463,7 @@ json5@^0.5.1:
   resolved "https://registry.yarnpkg.com/json5/-/json5-0.5.1.tgz#1eade7acc012034ad84e2396767ead9fa5495821"
   integrity sha1-Hq3nrMASA0rYTiOWdn6tn6VJWCE=
 
-json5@^2.1.2:
+json5@^2.1.2, json5@^2.1.3:
   version "2.2.0"
   resolved "https://registry.yarnpkg.com/json5/-/json5-2.2.0.tgz#2dfefe720c6ba525d9ebd909950f0515316c89a3"
   integrity sha512-f+8cldu7X/y7RAJurMEJmdoKXGB/X550w2Nr3tTbezL6RwEE/iMcm+tZnXeoZtKuOq6ft8+CqzEkrIgx1fPoQA==
@@ -9527,7 +9532,7 @@ resolve-path@^1.4.0:
     http-errors "~1.6.2"
     path-is-absolute "1.0.1"
 
-resolve@^1.10.0, resolve@^1.10.1, resolve@^1.11.0, resolve@^1.13.1, resolve@^1.20.0, resolve@^1.3.2:
+resolve@^1.10.0, resolve@^1.10.1, resolve@^1.11.0, resolve@^1.13.1, resolve@^1.17.0, resolve@^1.20.0, resolve@^1.3.2:
   version "1.20.0"
   resolved "https://registry.yarnpkg.com/resolve/-/resolve-1.20.0.tgz#629a013fb3f70755d6f0b7935cc1c2c5378b1975"
   integrity sha512-wENBPt4ySzg4ybFQW2TT1zMQucPK95HSh/nq2CFTZVOGut2+pQvSsgtda4d26YrYcr067wjbmzOG8byDPBX63A==
@@ -10608,6 +10613,18 @@ ts-morph@^12.0.0:
     "@ts-morph/common" "~0.11.0"
     code-block-writer "^10.1.1"
 
+tsconfig-resolver@^3.0.1:
+  version "3.0.1"
+  resolved "https://registry.yarnpkg.com/tsconfig-resolver/-/tsconfig-resolver-3.0.1.tgz#c9e62e328ecfbeaae4a4f1131a92cdbed12350c4"
+  integrity sha512-ZHqlstlQF449v8glscGRXzL6l2dZvASPCdXJRWG4gHEZlUVx2Jtmr+a2zeVG4LCsKhDXKRj5R3h0C/98UcVAQg==
+  dependencies:
+    "@types/json5" "^0.0.30"
+    "@types/resolve" "^1.17.0"
+    json5 "^2.1.3"
+    resolve "^1.17.0"
+    strip-bom "^4.0.0"
+    type-fest "^0.13.1"
+
 tslib@^1.8.1, tslib@^1.9.0:
   version "1.14.1"
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.14.1.tgz#cf2d38bdc34a134bcaf1091c41f6619e2f672d00"