core: add session diff API to show file changes between snapshots

packages/opencode/test/snapshot/snapshot.test.ts

@@ -33,7 +33,9 @@ test("tracks deleted files correctly", async () => {
 
       await $`rm ${tmp.path}/a.txt`.quiet()
 
-      expect((await Snapshot.patch(before!)).files).toContain(`${tmp.path}/a.txt`)
+      expect((await Snapshot.patch(before!)).files).toContain(
+        `${tmp.path}/a.txt`,
+      )
     },
   })
 })
@@ -91,11 +93,15 @@ test("multiple file operations", async () => {
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/a.txt`).text()).toBe(tmp.extra.aContent)
+      expect(await Bun.file(`${tmp.path}/a.txt`).text()).toBe(
+        tmp.extra.aContent,
+      )
       expect(await Bun.file(`${tmp.path}/c.txt`).exists()).toBe(false)
       // Note: revert currently only removes files, not directories
       // The empty directory will remain
-      expect(await Bun.file(`${tmp.path}/b.txt`).text()).toBe(tmp.extra.bContent)
+      expect(await Bun.file(`${tmp.path}/b.txt`).text()).toBe(
+        tmp.extra.bContent,
+      )
     },
   })
 })
@@ -123,7 +129,10 @@ test("binary file handling", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/image.png`, new Uint8Array([0x89, 0x50, 0x4e, 0x47]))
+      await Bun.write(
+        `${tmp.path}/image.png`,
+        new Uint8Array([0x89, 0x50, 0x4e, 0x47]),
+      )
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(`${tmp.path}/image.png`)
@@ -144,7 +153,9 @@ test("symlink handling", async () => {
 
       await $`ln -s ${tmp.path}/a.txt ${tmp.path}/link.txt`.quiet()
 
-      expect((await Snapshot.patch(before!)).files).toContain(`${tmp.path}/link.txt`)
+      expect((await Snapshot.patch(before!)).files).toContain(
+        `${tmp.path}/link.txt`,
+      )
     },
   })
 })
@@ -159,7 +170,9 @@ test("large file handling", async () => {
 
       await Bun.write(`${tmp.path}/large.txt`, "x".repeat(1024 * 1024))
 
-      expect((await Snapshot.patch(before!)).files).toContain(`${tmp.path}/large.txt`)
+      expect((await Snapshot.patch(before!)).files).toContain(
+        `${tmp.path}/large.txt`,
+      )
     },
   })
 })
@@ -177,7 +190,9 @@ test("nested directory revert", async () => {
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/level1/level2/level3/deep.txt`).exists()).toBe(false)
+      expect(
+        await Bun.file(`${tmp.path}/level1/level2/level3/deep.txt`).exists(),
+      ).toBe(false)
     },
   })
 })
@@ -211,7 +226,9 @@ test("revert with empty patches", async () => {
       expect(Snapshot.revert([])).resolves.toBeUndefined()
 
       // Should not crash with patches that have empty file lists
-      expect(Snapshot.revert([{ hash: "dummy", files: [] }])).resolves.toBeUndefined()
+      expect(
+        Snapshot.revert([{ hash: "dummy", files: [] }]),
+      ).resolves.toBeUndefined()
     },
   })
 })
@@ -526,9 +543,13 @@ test("restore function", async () => {
       await Snapshot.restore(before!)
 
       expect(await Bun.file(`${tmp.path}/a.txt`).exists()).toBe(true)
-      expect(await Bun.file(`${tmp.path}/a.txt`).text()).toBe(tmp.extra.aContent)
+      expect(await Bun.file(`${tmp.path}/a.txt`).text()).toBe(
+        tmp.extra.aContent,
+      )
       expect(await Bun.file(`${tmp.path}/new.txt`).exists()).toBe(true) // New files should remain
-      expect(await Bun.file(`${tmp.path}/b.txt`).text()).toBe(tmp.extra.bContent)
+      expect(await Bun.file(`${tmp.path}/b.txt`).text()).toBe(
+        tmp.extra.bContent,
+      )
     },
   })
 })
@@ -580,7 +601,66 @@ test("revert preserves file that existed in snapshot when deleted then recreated
 
       expect(await Bun.file(`${tmp.path}/newfile.txt`).exists()).toBe(false)
       expect(await Bun.file(`${tmp.path}/existing.txt`).exists()).toBe(true)
-      expect(await Bun.file(`${tmp.path}/existing.txt`).text()).toBe("original content")
+      expect(await Bun.file(`${tmp.path}/existing.txt`).text()).toBe(
+        "original content",
+      )
+    },
+  })
+})
+
+test("diffFull function", async () => {
+  await using tmp = await bootstrap()
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const before = await Snapshot.track()
+      expect(before).toBeTruthy()
+
+      await Bun.write(`${tmp.path}/new.txt`, "new content")
+      await Bun.write(`${tmp.path}/b.txt`, "modified content")
+
+      const after = await Snapshot.track()
+      expect(after).toBeTruthy()
+
+      const diffs = await Snapshot.diffFull(before!, after!)
+      expect(diffs.length).toBe(2)
+
+      const newFileDiff = diffs.find((d) => d.file === "new.txt")
+      expect(newFileDiff).toBeDefined()
+      expect(newFileDiff!.left).toBe("")
+      expect(newFileDiff!.right).toBe("new content")
+
+      const modifiedFileDiff = diffs.find((d) => d.file === "b.txt")
+      expect(modifiedFileDiff).toBeDefined()
+      expect(modifiedFileDiff!.left).toBe(tmp.extra.bContent)
+      expect(modifiedFileDiff!.right).toBe("modified content")
+    },
+  })
+
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const before = await Snapshot.track()
+      expect(before).toBeTruthy()
+
+      await Bun.write(`${tmp.path}/added.txt`, "added content")
+      await $`rm ${tmp.path}/a.txt`.quiet()
+
+      const after = await Snapshot.track()
+      expect(after).toBeTruthy()
+
+      const diffs = await Snapshot.diffFull(before!, after!)
+      expect(diffs.length).toBe(2)
+
+      const addedFileDiff = diffs.find((d) => d.file === "added.txt")
+      expect(addedFileDiff).toBeDefined()
+      expect(addedFileDiff!.left).toBe("")
+      expect(addedFileDiff!.right).toBe("added content")
+
+      const removedFileDiff = diffs.find((d) => d.file === "a.txt")
+      expect(removedFileDiff).toBeDefined()
+      expect(removedFileDiff!.left).toBe(tmp.extra.aContent)
+      expect(removedFileDiff!.right).toBe("")
     },
   })
 })