feat: watchConfig utility (#77)

README.md

@@ -16,6 +16,7 @@ Smart Configuration Loader.
 - Reads config from the nearest `package.json` file
 - [Extends configurations](https://github.com/unjs/c12#extending-configuration) from multiple local or git sources
 - Overwrite with [environment-specific configuration](#environment-specific-configuration)
+- Config watcher with auto reload
 
 ## Usage
 
@@ -36,10 +37,10 @@ Import:
 
 ```js
 // ESM
-import { loadConfig } from "c12";
+import { loadConfig, watchConfig } from "c12";
 
 // CommonJS
-const { loadConfig } = require("c12");
+const { loadConfig, watchConfig } = require("c12");
 ```
 
 Load configuration:
@@ -234,6 +235,29 @@ c12 tries to match [`envName`](#envname) and override environment config if spec
 }
 ```
 
+## Watching Configuration
+
+you can use `watchConfig` instead of `loadConfig` to load config and watch for changes, add and removals in all expected configuration paths and auto reload with new config,
+
+```ts
+import { watchConfig } from "c12";
+
+const config = watchConfig({
+  cwd: ".",
+  // chokidarOptions: {}, // Default is { ignoreInitial: true }
+  // debounce: 200 // Default is 100. You can set to fale to disable debounced watcher
+  onChange: ({ config, oldConfig, path, type }) => {
+    console.log("[watcher]", type, path);
+  },
+});
+
+console.log("initial config", config.config, config.layers);
+console.log("watching config files:", config.watchingFiles);
+
+// When exiting process
+await config.unwatch();
+```
+
 ## 💻 Development
 
 - Clone this repository

package.json

@@ -30,12 +30,14 @@
     "test:types": "tsc --noEmit"
   },
   "dependencies": {
+    "chokidar": "^3.5.3",
     "defu": "^6.1.2",
     "dotenv": "^16.0.3",
     "giget": "^1.1.2",
     "jiti": "^1.18.2",
     "mlly": "^1.2.0",
     "pathe": "^1.1.0",
+    "perfect-debounce": "^0.1.3",
     "pkg-types": "^1.0.2",
     "rc9": "^2.1.0"
   },

test/test.ts → playground/load.ts

@@ -4,7 +4,7 @@ import { loadConfig } from "../src";
 const r = (path: string) => fileURLToPath(new URL(path, import.meta.url));
 
 async function main() {
-  const fixtureDir = r("./fixture");
+  const fixtureDir = r("../test/fixture");
   const config = await loadConfig({ cwd: fixtureDir, dotenv: true });
   console.log(config);
 }

playground/watch.ts

@@ -0,0 +1,27 @@
+import { fileURLToPath } from "node:url";
+import { watchConfig } from "../src";
+
+const r = (path: string) => fileURLToPath(new URL(path, import.meta.url));
+
+async function main() {
+  const fixtureDir = r("../test/fixture");
+  const config = await watchConfig({
+    cwd: fixtureDir,
+    dotenv: true,
+    packageJson: ["c12", "c12-alt"],
+    globalRc: true,
+    envName: "test",
+    extend: {
+      extendKey: ["theme", "extends"],
+    },
+    onChange: ({ config, path, type }) => {
+      console.log("[watcher]", type, path);
+      console.log(config.config);
+    },
+  });
+  console.log("initial config", config.config, config.layers);
+  console.log("watching config files:", config.watchingFiles);
+}
+
+// eslint-disable-next-line unicorn/prefer-top-level-await
+main().catch(console.error);

src/index.ts

@@ -1,3 +1,4 @@
 export * from "./dotenv";
 export * from "./loader";
 export * from "./types";
+export * from "./watch";