From 79f978ddebcac0686fb26d26c4e424ef60fe0390 Mon Sep 17 00:00:00 2001
From: Daniel Dietzler <36593685+danieldietzler@users.noreply.github.com>
Date: Thu, 19 Mar 2026 18:17:56 +0100
Subject: [PATCH] fix: writing empty exif tags (#27025)

---
 .../src/repositories/metadata.repository.ts   |  6 +-
 server/src/services/metadata.service.ts       |  2 +-
 .../repositories/metadata.repository.spec.ts  | 75 +++++++++++++++++++
 3 files changed, 81 insertions(+), 2 deletions(-)
 create mode 100644 server/test/medium/specs/repositories/metadata.repository.spec.ts

diff --git a/server/src/repositories/metadata.repository.ts b/server/src/repositories/metadata.repository.ts
index fc00d44b3f..57c688cac2 100644
--- a/server/src/repositories/metadata.repository.ts
+++ b/server/src/repositories/metadata.repository.ts
@@ -119,8 +119,12 @@ export class MetadataRepository {
   }
 
   async writeTags(path: string, tags: Partial<Tags>): Promise<void> {
+    // If exiftool assigns a field with ^= instead of =, empty values will be written too.
+    // Since exiftool-vendored doesn't support an option for this, we append the ^ to the name of the tag instead.
+    // https://exiftool.org/exiftool_pod.html#:~:text=is%20used%20to%20write%20an%20empty%20string
+    const tagsToWrite = Object.fromEntries(Object.entries(tags).map(([key, value]) => [`${key}^`, value]));
     try {
-      await this.exiftool.write(path, tags);
+      await this.exiftool.write(path, tagsToWrite);
     } catch (error) {
       this.logger.warn(`Error writing exif data (${path}): ${error}`);
     }
diff --git a/server/src/services/metadata.service.ts b/server/src/services/metadata.service.ts
index d2467ae6d9..7b87ea06a6 100644
--- a/server/src/services/metadata.service.ts
+++ b/server/src/services/metadata.service.ts
@@ -467,7 +467,7 @@ export class MetadataService extends BaseService {
         GPSLatitude: latitude,
         GPSLongitude: longitude,
         Rating: rating,
-        TagsList: tags?.length ? tags : undefined,
+        TagsList: tags,
       },
       _.isUndefined,
     );
diff --git a/server/test/medium/specs/repositories/metadata.repository.spec.ts b/server/test/medium/specs/repositories/metadata.repository.spec.ts
new file mode 100644
index 0000000000..976f33695e
--- /dev/null
+++ b/server/test/medium/specs/repositories/metadata.repository.spec.ts
@@ -0,0 +1,75 @@
+import { Kysely } from 'kysely';
+import { mkdtempSync, readFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { LoggingRepository } from 'src/repositories/logging.repository';
+import { MetadataRepository } from 'src/repositories/metadata.repository';
+import { DB } from 'src/schema';
+import { BaseService } from 'src/services/base.service';
+import { newMediumService } from 'test/medium.factory';
+import { newDate } from 'test/small.factory';
+import { getKyselyDB } from 'test/utils';
+
+let database: Kysely<DB>;
+
+const setup = () => {
+  const { ctx } = newMediumService(BaseService, {
+    database,
+    real: [],
+    mock: [LoggingRepository],
+  });
+  return { ctx, sut: ctx.get(MetadataRepository) };
+};
+
+beforeAll(async () => {
+  database = await getKyselyDB();
+});
+
+describe(MetadataRepository.name, () => {
+  describe('writeTags', () => {
+    it('should write an empty description', async () => {
+      const { sut } = setup();
+      const dir = mkdtempSync(join(tmpdir(), 'metadata-medium-write-tags'));
+      const sidecarFile = join(dir, 'sidecar.xmp');
+
+      await sut.writeTags(sidecarFile, { Description: '' });
+      expect(readFileSync(sidecarFile).toString()).toEqual(expect.stringContaining('rdf:Description'));
+    });
+
+    it('should write an empty tags list', async () => {
+      const { sut } = setup();
+      const dir = mkdtempSync(join(tmpdir(), 'metadata-medium-write-tags'));
+      const sidecarFile = join(dir, 'sidecar.xmp');
+
+      await sut.writeTags(sidecarFile, { TagsList: [] });
+      const fileContent = readFileSync(sidecarFile).toString();
+      expect(fileContent).toEqual(expect.stringContaining('digiKam:TagsList'));
+      expect(fileContent).toEqual(expect.stringContaining('<rdf:li/>'));
+    });
+  });
+
+  it('should write tags', async () => {
+    const { sut } = setup();
+    const dir = mkdtempSync(join(tmpdir(), 'metadata-medium-write-tags'));
+    const sidecarFile = join(dir, 'sidecar.xmp');
+
+    await sut.writeTags(sidecarFile, {
+      Description: 'my-description',
+      ImageDescription: 'my-image-description',
+      DateTimeOriginal: newDate().toISOString(),
+      GPSLatitude: 42,
+      GPSLongitude: 69,
+      Rating: 3,
+      TagsList: ['tagA'],
+    });
+
+    const fileContent = readFileSync(sidecarFile).toString();
+    expect(fileContent).toEqual(expect.stringContaining('my-description'));
+    expect(fileContent).toEqual(expect.stringContaining('my-image-description'));
+    expect(fileContent).toEqual(expect.stringContaining('exif:DateTimeOriginal'));
+    expect(fileContent).toEqual(expect.stringContaining('<exif:GPSLatitude>42,0.0N</exif:GPSLatitude>'));
+    expect(fileContent).toEqual(expect.stringContaining('<exif:GPSLongitude>69,0.0E</exif:GPSLongitude>'));
+    expect(fileContent).toEqual(expect.stringContaining('<xmp:Rating>3</xmp:Rating>'));
+    expect(fileContent).toEqual(expect.stringContaining('tagA'));
+  });
+});