From 01db549c7cddb9a4e2ebe4477ff440abbd5940b8 Mon Sep 17 00:00:00 2001
From: Felipe Cabrera <me@felieppe.com>
Date: Wed, 5 Aug 2026 20:53:30 -0300
Subject: [PATCH] fix(web): flag metadata fields missing from only some
 duplicates

---
 web/src/lib/utils/duplicate-utils.spec.ts | 89 +++++++++++++++++++++++
 web/src/lib/utils/duplicate-utils.ts      |  9 ++-
 2 files changed, 95 insertions(+), 3 deletions(-)
 create mode 100644 web/src/lib/utils/duplicate-utils.spec.ts

diff --git a/web/src/lib/utils/duplicate-utils.spec.ts b/web/src/lib/utils/duplicate-utils.spec.ts
new file mode 100644
index 0000000000..846b22f6e2
--- /dev/null
+++ b/web/src/lib/utils/duplicate-utils.spec.ts
@@ -0,0 +1,89 @@
+import type { AssetResponseDto, ExifResponseDto } from '@immich/sdk';
+import { computeDifferingMetadataFields, countDifferingMetadataItems } from '$lib/utils/duplicate-utils';
+import { assetFactory } from '@test-data/factories/asset-factory';
+
+// Derives both assets from a single base so that everything except `exifInfo` is identical,
+// leaving the field under test as the only possible difference.
+const buildPair = (first: ExifResponseDto, second: ExifResponseDto): AssetResponseDto[] => {
+  const base = assetFactory.build();
+  return [
+    { ...base, id: 'first-asset', exifInfo: first },
+    { ...base, id: 'second-asset', exifInfo: second },
+  ];
+};
+
+describe('computeDifferingMetadataFields', () => {
+  it('flags coordinates when only one asset has them', () => {
+    const assets = buildPair({ latitude: 48.8583, longitude: 2.2944 }, {});
+
+    const diffs = computeDifferingMetadataFields(assets);
+
+    expect(diffs.latitude).toBe(true);
+    expect(diffs.longitude).toBe(true);
+  });
+
+  it('does not flag coordinates when neither asset has them', () => {
+    const assets = buildPair({}, {});
+
+    const diffs = computeDifferingMetadataFields(assets);
+
+    expect(diffs.latitude).toBe(false);
+    expect(diffs.longitude).toBe(false);
+  });
+
+  it('does not flag coordinates when both assets share them', () => {
+    const coordinates = { latitude: 48.8583, longitude: 2.2944 };
+    const assets = buildPair(coordinates, { ...coordinates });
+
+    const diffs = computeDifferingMetadataFields(assets);
+
+    expect(diffs.latitude).toBe(false);
+    expect(diffs.longitude).toBe(false);
+  });
+
+  it('flags coordinates when the assets disagree', () => {
+    const assets = buildPair({ latitude: 48.8583, longitude: 2.2944 }, { latitude: 41.8902, longitude: 12.4922 });
+
+    const diffs = computeDifferingMetadataFields(assets);
+
+    expect(diffs.latitude).toBe(true);
+    expect(diffs.longitude).toBe(true);
+  });
+
+  it('treats an explicit null the same as an absent field', () => {
+    const assets = buildPair({ description: null }, {});
+
+    const diffs = computeDifferingMetadataFields(assets);
+
+    expect(diffs.description).toBe(false);
+  });
+
+  it('treats an empty string the same as an absent field', () => {
+    const assets = buildPair({ description: '' }, { description: null });
+
+    const diffs = computeDifferingMetadataFields(assets);
+
+    expect(diffs.description).toBe(false);
+  });
+
+  it('flags other nullable fields present on only one asset', () => {
+    const assets = buildPair({ rating: 4, lensModel: 'EF24-70mm f/2.8L II USM', make: 'Canon' }, {});
+
+    const diffs = computeDifferingMetadataFields(assets);
+
+    expect(diffs.rating).toBe(true);
+    expect(diffs.lensModel).toBe(true);
+    expect(diffs.make).toBe(true);
+  });
+});
+
+describe('countDifferingMetadataItems', () => {
+  it('counts a field that only one asset has', () => {
+    const assets = buildPair({ latitude: 48.8583, longitude: 2.2944 }, {});
+
+    const diffs = computeDifferingMetadataFields(assets);
+
+    // latitude and longitude belong to the single "gps" field
+    expect(countDifferingMetadataItems(diffs)).toBe(1);
+  });
+});
diff --git a/web/src/lib/utils/duplicate-utils.ts b/web/src/lib/utils/duplicate-utils.ts
index 86b221906f..fb6dd44b11 100644
--- a/web/src/lib/utils/duplicate-utils.ts
+++ b/web/src/lib/utils/duplicate-utils.ts
@@ -27,6 +27,11 @@ import type { MessageFormatter } from 'svelte-i18n';
 import { getAssetResolution, getFileSize } from '$lib/utils/asset-utils';
 import { fromISODateTime, fromISODateTimeUTC } from '$lib/utils/timeline-util';
 
+// Stands in for a value that is absent, so that "present on one asset, absent on another" counts as a difference.
+// Every value below collapses to it, since the metadata renderers fall back to "unknown" for each of them.
+const MISSING = Symbol('missing');
+const MISSING_VALUES = new Set<unknown>([undefined, null, '']);
+
 const truncateMiddle = (path: string, maxLength = 50): string => {
   if (path.length <= maxLength) {
     return path;
@@ -289,9 +294,7 @@ export const computeDifferingMetadataFields = (assets: AssetResponseDto[]): Diff
 
     for (const asset of assets) {
       const value = getValueForAsset(asset, key);
-      if (value !== undefined && value !== null) {
-        uniqueValues.add(normalizeForComparison(key, value));
-      }
+      uniqueValues.add(MISSING_VALUES.has(value) ? MISSING : normalizeForComparison(key, value));
     }
 
     diffs[key] = uniqueValues.size > 1;