Photo: one async method per EXIF field (closes #148)

`Photo` gains thirteen async methods, one per `PhotoExif` field and named after it: `make()`, `model()`, `lensModel()`, `dateTimeOriginal()`, `offsetTimeOriginal()`, `exposureTime()`, `fNumber()`, `iso()`, `focalLength()`, `orientation()`, `gpsLatitude()`, `gpsLongitude()` and `gpsAltitude()`. Each calls `exif()` and returns its one field, or `undefined` when the file lacks it. `exif()` is unchanged.

`Photo` implements a type built from `PhotoExif`'s keys, so the type check fails when a field has no method. Each call reads the original again; a caller that wants several fields calls `exif()` once.

Model: opus-5-5

README.md

@@ -726,7 +726,7 @@ synchronous getters look at the disk and never touch the network:
 - `photo.isLocal` → `boolean` — whether the whole original is at `savePath`. A
   copy only in the cache does not count.
 
-Five async methods may download:
+These async methods may download:
 
 - `await photo.original(opts?)` → `{ path, bytes, videoPath? }` — the
   full-resolution file. For a live photo, `path` and `bytes` are its image's and
@@ -748,6 +748,12 @@ Five async methods may download:
   UTC. EXIF is read from any image format exifreader reads (such as JPEG,
   HEIC/HEIF, AVIF, PNG, WebP and TIFF), a live photo's image included. Any other
   original gives `{}`, and a video gives `{}` without being downloaded.
+- `await photo.make(opts?)`, and likewise `model()`, `lensModel()`,
+  `dateTimeOriginal()`, `offsetTimeOriginal()`, `exposureTime()`, `fNumber()`,
+  `iso()`, `focalLength()`, `orientation()`, `gpsLatitude()`, `gpsLongitude()`
+  and `gpsAltitude()` → one field of `exif()` each, typed as in `PhotoExif`, or
+  `undefined` when the file lacks it. Each calls `exif()` with its `opts`, so
+  each call reads the original again.
 
 They serve from the on-disk content cache when the bytes are present and
 otherwise fetch through the pools; `original()`, `content()` and `exif()` also

TODO.md

@@ -25,6 +25,16 @@ declares one.
 
 # Completed Steps
 
+- 2026-10-01: A `Photo` has one async method for each field of `exif()`, named
+  and typed as in `PhotoExif`: `make()`, `model()`, `lensModel()`,
+  `dateTimeOriginal()`, `offsetTimeOriginal()`, `exposureTime()`, `fNumber()`,
+  `iso()`, `focalLength()`, `orientation()`, `gpsLatitude()`, `gpsLongitude()`
+  and `gpsAltitude()` (issue 148). Each calls `exif()` and returns its one
+  field, or undefined when the file lacks it. `Photo` implements a type with one
+  method per `PhotoExif` field, so the build's type check fails when a field has
+  no method. A test checks, on the JPEG and the HEIC, that each method gives the
+  same value as `exif()`.
+
 - 2026-10-01: Each original's save path is
   `YYYY/YYYY-MM/YYYY-MM-DD/YYYY-MM-DD.<fileID>.<ext>` under the library's
   download directory, which defaults to `photos` in the working directory (issue

src/library/read.ts

@@ -12,11 +12,11 @@
 // plain records are the serializable surface, and `record()` returns one.
 //
 // A `Photo` also fetches its own bytes: `original()`, `thumbnail()`,
-// `download()`, `content()` and `exif()` go through the on-disk content cache
+// `download()`, `content()`, `exif()` and the methods that each return one
-// (issue #46), and are the one place in this module that may touch the
+// field of `exif()` go through the on-disk content cache (issue #46), and are
-// network. A library opened without a content source leaves that cache absent,
+// the one place in this module that may touch the network. A library opened
-// and those methods then throw. `savePath` and `isLocal` look only at the disk
+// without a content source leaves that cache absent, and those methods then
-// and need no cache.
+// throw. `savePath` and `isLocal` look only at the disk and need no cache.
 
 import { readFile } from "node:fs/promises";
 
@@ -42,11 +42,18 @@ const byNewest = (a: PhotoRecord, b: PhotoRecord): number =>
 const byNewestAlbum = (a: AlbumRecord, b: AlbumRecord): number =>
     b.updationTime - a.updationTime || b.collectionID - a.collectionID;
 
+// A method for each `PhotoExif` field, named after it, taking the options
+// `exif()` takes and giving that field. `Photo` implements it, so the build's
+// type check fails when `PhotoExif` has a field `Photo` has no method for.
+type PhotoExifMethods = {
+    [K in keyof PhotoExif]-?: (opts?: ContentOptions) => Promise<PhotoExif[K]>;
+};
+
 // A single photo. Field access mirrors `PhotoRecord`; `record()` returns the
 // underlying plain record for callers that need the IPC-safe value. `file` is
 // the membership the record is read from, so the save path carries the date of
 // `takenAt` and stays known after a refresh removes the file from the library.
-export class Photo {
+export class Photo implements PhotoExifMethods {
     constructor(
         private readonly rec: PhotoRecord,
         private readonly file: EnteFile,
@@ -160,6 +167,65 @@ export class Photo {
         return readPhotoExif(await this.content(opts));
     }
 
+    // One field of `exif()` each, named and typed as in `PhotoExif`, and
+    // undefined when the file lacks it. Each call runs `exif()`, which reads
+    // the original again.
+    async make(opts?: ContentOptions): Promise<PhotoExif["make"]> {
+        return (await this.exif(opts)).make;
+    }
+    async model(opts?: ContentOptions): Promise<PhotoExif["model"]> {
+        return (await this.exif(opts)).model;
+    }
+    async lensModel(opts?: ContentOptions): Promise<PhotoExif["lensModel"]> {
+        return (await this.exif(opts)).lensModel;
+    }
+    async dateTimeOriginal(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["dateTimeOriginal"]> {
+        return (await this.exif(opts)).dateTimeOriginal;
+    }
+    async offsetTimeOriginal(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["offsetTimeOriginal"]> {
+        return (await this.exif(opts)).offsetTimeOriginal;
+    }
+    async exposureTime(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["exposureTime"]> {
+        return (await this.exif(opts)).exposureTime;
+    }
+    async fNumber(opts?: ContentOptions): Promise<PhotoExif["fNumber"]> {
+        return (await this.exif(opts)).fNumber;
+    }
+    async iso(opts?: ContentOptions): Promise<PhotoExif["iso"]> {
+        return (await this.exif(opts)).iso;
+    }
+    async focalLength(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["focalLength"]> {
+        return (await this.exif(opts)).focalLength;
+    }
+    async orientation(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["orientation"]> {
+        return (await this.exif(opts)).orientation;
+    }
+    async gpsLatitude(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["gpsLatitude"]> {
+        return (await this.exif(opts)).gpsLatitude;
+    }
+    async gpsLongitude(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["gpsLongitude"]> {
+        return (await this.exif(opts)).gpsLongitude;
+    }
+    async gpsAltitude(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["gpsAltitude"]> {
+        return (await this.exif(opts)).gpsAltitude;
+    }
+
     private cacheOrThrow(): PhotoContent {
         if (!this.cache) {
             throw new Error(

test/library/content-library.test.ts

@@ -7,7 +7,7 @@
  * a cached path shows up on the projected record. A library opened without a
  * content source leaves those methods throwing rather than silently doing
  * nothing. It also covers a `Photo`'s `savePath`, `isLocal`, `download()`,
- * `content()` and `exif()`.
+ * `content()`, `exif()` and the methods that each return one field of `exif()`.
  */
 
 import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
@@ -644,8 +644,8 @@ describe("Photo save path, local copy, content and EXIF", () => {
         await lib.close();
     });
 
-    // What exif() returns for HEIC_WITH_EXIF, which holds the same values as
+    // What exif() returns for HEIC_WITH_EXIF, and for JPEG_WITH_EXIF, which
-    // JPEG_WITH_EXIF.
+    // holds the same values.
     const heicFields: PhotoExif = {
         make: "Canon",
         model: "EOS R5",
@@ -686,9 +686,35 @@ describe("Photo save path, local copy, content and EXIF", () => {
         await lib.close();
     });
 
+    // The build's type check, not this test, makes sure `Photo` has a method
+    // for every `PhotoExif` field, whatever the fixtures hold: `Photo`
+    // implements a type with one method per field. This test checks that each
+    // method gives the same value as exif().
+    it.each([
+        ["JPEG", JPEG_WITH_EXIF],
+        ["HEIC", HEIC_WITH_EXIF],
+    ])(
+        "has a method for each field exif() returns, giving the same value, for a %s",
+        async (_, bytes) => {
+            const lib = await open({ contentSource: stubSource(bytes) });
+            const photo = lib.photos.byID({ fileID: 1 })!;
+            const exif = await photo.exif();
+            // The file holds every field, so every method is checked.
+            expect(exif).toStrictEqual(heicFields);
+            for (const [field, value] of Object.entries(exif)) {
+                expect(await photo[field as keyof PhotoExif]()).toStrictEqual(
+                    value,
+                );
+            }
+            await lib.close();
+        },
+    );
+
     it("returns no EXIF fields for an original that is not an image", async () => {
         const lib = await open();
-        expect(await lib.photos.byID({ fileID: 1 })!.exif()).toStrictEqual({});
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        expect(await photo.exif()).toStrictEqual({});
+        expect(await photo.dateTimeOriginal()).toBeUndefined();
         await lib.close();
     });