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

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
-    // JPEG_WITH_EXIF.
+    // What exif() returns for HEIC_WITH_EXIF, and for JPEG_WITH_EXIF, which
+    // 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();
     });