feat(parser): Add exception for removing unused keys

README.md

@@ -503,6 +503,7 @@ Below are the configuration options with their default values:
     compatibilityJSON: 'v3', // One of: 'v1', 'v2', 'v3', 'v4
     debug: false,
     removeUnusedKeys: false,
+    filterUnusedKeys: false,
     sort: false,
     attr: {
         list: ['data-i18n'],
@@ -574,6 +575,28 @@ Type: `Boolean` Default: `false`
 
 Set to `true` to remove unused translation keys from i18n resource files.
 
+#### filterUnusedKeys
+
+Type: `Object` Default: `false`
+
+If an `Object` is supplied and `removeUnusedKeys` is set to `true`, to leave specific keys you can specify a function like so:
+```js
+filterUnusedKeys: ({ lng, ns, unusedKey }) => {
+  if (ns === 'resource') {
+    const exceptionKeys = ['word', 'key.word', ...];
+    if (exceptionKeys.includes(unusedKey)) {
+      // leave key
+      return true;
+    }
+  }
+  if (ns === 'other_resource') {
+    // leave key
+    return true;
+  }
+  // remove key
+  return false;
+}
+
 #### sort
 
 Type: `Boolean` Default: `false`

src/parser.js

@@ -796,10 +796,40 @@ class Parser {
           const resStoreKeys = flattenObjectKeys(_.get(this.resStore, [lng, ns], {}));
           const resScanKeys = flattenObjectKeys(_.get(this.resScan, [lng, ns], {}));
           const unusedKeys = _.differenceWith(resStoreKeys, resScanKeys, _.isEqual);
+          let filteredKey;
 
           for (let i = 0; i < unusedKeys.length; ++i) {
-            _.unset(resMerged[lng][ns], unusedKeys[i]);
-            this.log(`Removed an unused translation key { ${chalk.red(JSON.stringify(unusedKeys[i]))} from ${chalk.red(JSON.stringify(this.formatResourceLoadPath(lng, ns)))}`);
+            filteredKey = false;
+
+            if (
+              this.options.filterUnusedKeys &&
+              typeof this.options.filterUnusedKeys === 'function'
+            ) {
+              filteredKey = this.options.filterUnusedKeys({
+                lng,
+                ns,
+                unusedKey: unusedKeys[i].toString().replaceAll(',', '.'),
+              });
+            }
+
+            if (!filteredKey) {
+              _.unset(resMerged[lng][ns], unusedKeys[i]);
+              this.log(
+                `Removed an unused translation key { ${chalk.red(
+                  JSON.stringify(unusedKeys[i])
+                )} } from ${chalk.red(
+                  JSON.stringify(this.formatResourceLoadPath(lng, ns))
+                )}`
+              );
+              continue;
+            }
+            this.log(
+              `Skipped removing an unused translation key { ${chalk.yellow(
+                JSON.stringify(unusedKeys[i])
+              )} } from ${chalk.yellow(
+                JSON.stringify(this.formatResourceLoadPath(lng, ns))
+              )}`
+            );
           }
 
           // Omit empty object