feat(studio-server): a write receipt names the version the write replaced

packages/studio-server/src/helpers/applyFileMutations.test.ts

@@ -105,6 +105,27 @@ describe("applyFileMutations", () => {
     expectStaleMutation("after", false);
   });
 
+  it("leaves a receipt saying which bytes the write started from", () => {
+    resetFileWriteReceipts();
+    const projectDir = mkdtempSync(join(tmpdir(), "hf-mutation-from-"));
+    const path = join(projectDir, "index.html");
+    try {
+      // Someone else's change lands before the patch reads the file: the receipt names it as the start.
+      writeFileSync(path, "external", "utf8");
+      applyFileMutations(
+        projectDir,
+        [{ sourceFile: "index.html", absPath: path, after: "patched" }],
+        "hand",
+      );
+      expect(identifyFileWrite(path, fileContentVersion("patched"))).toMatchObject({
+        writeToken: "hand",
+        from: fileContentVersion("external"),
+      });
+    } finally {
+      rmSync(projectDir, { recursive: true, force: true });
+    }
+  });
+
   it("clears receipts for writes rolled back after a partial batch", () => {
     resetFileWriteReceipts();
     const projectDir = mkdtempSync(join(tmpdir(), "hf-mutation-rollback-"));

packages/studio-server/src/helpers/fileVersion.test.ts

@@ -109,6 +109,29 @@ describe("file versions and write receipts", () => {
     expect(identifyFileWrite("/project/index.html", first.version)).toEqual(first);
   });
 
+  it("says which version a write replaced when the writer read it, and nothing when it did not", () => {
+    const version = fileContentVersion("<h1>Title!</h1>");
+    recordFileWriteReceipt("/project/index.html", {
+      path: "index.html",
+      version,
+      writeToken: "hand",
+      overwrote: "<h1>Title</h1>",
+    });
+    expect(identifyFileWrite("/project/index.html", version)).toEqual({
+      path: "index.html",
+      version,
+      writeToken: "hand",
+      from: fileContentVersion("<h1>Title</h1>"),
+    });
+    const restored = fileContentVersion("<h1>Old</h1>");
+    recordFileWriteReceipt("/project/index.html", {
+      path: "index.html",
+      version: restored,
+      writeToken: "restore",
+    });
+    expect(identifyFileWrite("/project/index.html", restored)).not.toHaveProperty("from");
+  });
+
   it("labels a repeat of earlier bytes with the newest token, not the spent one", () => {
     const version = fileContentVersion("same bytes");
     const older = { path: "index.html", version, writeToken: "write-older" };

packages/studio-server/src/helpers/fileVersion.ts

@@ -5,6 +5,7 @@ export interface FileWriteReceipt {
   path: string;
   version: string;
   writeToken: string;
+  from?: string;
 }
 
 interface StoredReceipt extends FileWriteReceipt {
@@ -70,7 +71,11 @@ export function recordFileWriteReceipt(
     if (live.length > 0) receipts.set(path, live);
     else receipts.delete(path);
   }
-  receipts.set(absPath, [...(receipts.get(absPath) ?? []), { ...receipt, recordedAt: now }]);
+  const from = overwrote === undefined ? undefined : fileContentVersion(overwrote);
+  receipts.set(absPath, [
+    ...(receipts.get(absPath) ?? []),
+    { ...receipt, ...(from && { from }), recordedAt: now },
+  ]);
 }
 
 export function clearFileWriteReceipt(filePath: string, version: string, writeToken: string): void {
@@ -96,8 +101,8 @@ export function identifyFileWrite(
 ): FileWriteReceipt | null {
   const receipt = newestReceipt(realFilePath(filePath), expectedVersion);
   if (!receipt) return null;
-  const { path, version, writeToken } = receipt;
-  return { path, version, writeToken };
+  const { path, version, writeToken, from } = receipt;
+  return { path, version, writeToken, ...(from && { from }) };
 }
 
 function newestReceipt(absPath: string, expectedVersion: string): StoredReceipt | undefined {

packages/studio-server/src/routes/files.test.ts

@@ -158,6 +158,7 @@ describe("registerFileRoutes", () => {
       path: "index.html",
       version: result.version,
       writeToken: "studio-insert-1",
+      from: fileContentVersion(before),
     });
 
     const committed = result.after;
@@ -428,6 +429,7 @@ describe("registerFileRoutes", () => {
       path: "image.png",
       version: payload.version,
       writeToken: "binary-write",
+      from: fileContentVersion(before),
     });
   });
 
@@ -541,6 +543,7 @@ describe("registerFileRoutes", () => {
       path: "index.html",
       version: payload.version,
       writeToken: "studio-write-1",
+      from: fileContentVersion("before"),
     });
     expect(payload.backupPath).toMatch(/^\.hyperframes\/backup\//);
     expect(readFileSync(join(projectDir, payload.backupPath!), "utf-8")).toBe("before");
@@ -734,6 +737,7 @@ describe("registerFileRoutes", () => {
       path: "index.html",
       version,
       writeToken: "studio-patch-1",
+      from: fileContentVersion('<div id="title">Before</div>'),
     });
   });
 
@@ -780,6 +784,7 @@ describe("registerFileRoutes", () => {
       path: "index.html",
       version,
       writeToken: "studio-layer-order-1",
+      from: fileContentVersion(original),
     });
     expect(readdirSync(join(projectDir, ".hyperframes", "backup"))).toHaveLength(1);
   });
@@ -884,6 +889,7 @@ describe("registerFileRoutes", () => {
         path: file.sourceFile,
         version,
         writeToken: "studio-group-drag-1",
+        from: fileContentVersion(`<div id="${file.sourceFile.replace(".html", "")}">Before</div>`),
       });
     }
   });
@@ -1105,6 +1111,7 @@ describe("registerFileRoutes", () => {
       path: "index.html",
       version: payload.files[0].version,
       writeToken: "cut-test",
+      from: fileContentVersion(before),
     });
   });