fix: clarify invalid config JSON errors

src/config/store.ts

@@ -35,7 +35,19 @@ export function getHistoryPath(): string {
 export async function loadConfig(): Promise<Config> {
   const configPath = getConfigPath();
   const raw = await readFile(configPath, 'utf-8');
-  const parsed = JSON.parse(raw) as Partial<Config>;
+  let parsed: Partial<Config>;
+
+  try {
+    parsed = JSON.parse(raw) as Partial<Config>;
+  } catch (error) {
+    if (error instanceof SyntaxError) {
+      throw new Error(
+        `Invalid JSON in config file: ${configPath}. Fix the JSON syntax or run \`commit-echo init\` to recreate it.`,
+        { cause: error },
+      );
+    }
+    throw error;
+  }
 
   return {
     provider: parsed.provider ?? '',

tests/config-store.test.mjs

@@ -0,0 +1,46 @@
+import assert from "node:assert/strict";
+import { mkdir, mkdtemp, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { dirname } from "node:path";
+import test from "node:test";
+
+import { getConfigPath, loadConfig } from "../dist/config/store.js";
+
+function escapeRegExp(value) {
+  return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+}
+
+test("loadConfig reports invalid JSON with the config path and fix hint", async () => {
+  const originalHome = process.env.HOME;
+  const originalXdgConfigHome = process.env.XDG_CONFIG_HOME;
+  const home = await mkdtemp(`${tmpdir()}/commit-echo-config-`);
+
+  process.env.HOME = home;
+  delete process.env.XDG_CONFIG_HOME;
+
+  try {
+    const configPath = getConfigPath();
+    await mkdir(dirname(configPath), { recursive: true });
+    await writeFile(configPath, "{ invalid json", "utf-8");
+
+    await assert.rejects(loadConfig(), (error) => {
+      assert.equal(error instanceof Error, true);
+      assert.match(error.message, /Invalid JSON in config file:/);
+      assert.match(error.message, new RegExp(escapeRegExp(configPath)));
+      assert.match(error.message, /Fix the JSON syntax or run `commit-echo init` to recreate it\./);
+      return true;
+    });
+  } finally {
+    if (originalHome === undefined) {
+      delete process.env.HOME;
+    } else {
+      process.env.HOME = originalHome;
+    }
+
+    if (originalXdgConfigHome === undefined) {
+      delete process.env.XDG_CONFIG_HOME;
+    } else {
+      process.env.XDG_CONFIG_HOME = originalXdgConfigHome;
+    }
+  }
+});