fix(prisma): inherit database region from the project's default region

packages/alchemy/src/Prisma/Database.ts

@@ -6,6 +6,7 @@ import {
   deleteDatabase,
   getDatabases,
   getDatabase,
+  getProject,
   getProjectBranches,
   getProjectDatabases,
   updateDatabase,
@@ -136,7 +137,8 @@ export interface DatabaseProps {
    */
   name?: string;
   /**
-   * Region for the database.
+   * Region for the database. `"inherit"` uses the project's default region,
+   * or the default database's region when the project has none.
    *
    * @default "us-east-1"
    */
@@ -437,12 +439,16 @@ const resolveDatabaseRegion = Effect.fn(function* (
   if (region !== "inherit") {
     return (region ?? "us-east-1") as PrismaRegionId;
   }
+  const project = yield* getProject({ id: projectId });
+  if (project.data.defaultRegion !== null) {
+    return project.data.defaultRegion as PrismaRegionId;
+  }
   const database = yield* findDefaultDatabase(projectId);
   const inherited = database?.region?.id;
   if (inherited === undefined) {
     return yield* Effect.fail(
       new Error(
-        `Cannot resolve Prisma database region 'inherit' because project '${projectId}' has no default database region. Create or promote a default database first, or specify an explicit region.`,
+        `Cannot resolve Prisma database region 'inherit' because project '${projectId}' has no default region and no default database region. Create or promote a default database first, or specify an explicit region.`,
       ),
     );
   }

packages/alchemy/test/Prisma/Database.test.ts

@@ -365,3 +365,55 @@ test.provider(
   }),
   { tags: logicalIdTags, timeout: 180_000 },
 );
+
+test.provider(
+  "region inherit uses the project default region when the project has no default database",
+  Effect.fn(function* (stack: Test.ScratchStack) {
+    yield* stack.destroy();
+
+    const resources = Effect.gen(function* () {
+      const project = yield* Prisma.Project("Project", {
+        createDatabase: false,
+        region: "eu-central-1",
+      });
+      const database = yield* Prisma.Database("Inherited", { project, region: "inherit" });
+      return { project, database };
+    });
+
+    const initial = yield* stack.deploy(resources);
+    expect((yield* getProject({ id: initial.project.projectId })).data.defaultRegion).toBe(
+      "eu-central-1",
+    );
+    expect(initial.database.region).toBe("eu-central-1");
+    expect((yield* observeDatabase(initial.database.databaseId)).region?.id).toBe("eu-central-1");
+
+    const repeated = yield* stack.deploy(resources);
+    expect(repeated.database.databaseId).toBe(initial.database.databaseId);
+
+    yield* stack.destroy();
+    yield* expectDatabaseGone(initial.database.databaseId);
+    yield* expectProjectGone(initial.project.projectId);
+  }),
+  { tags: logicalIdTags, timeout: 180_000 },
+);
+
+test.provider(
+  "region inherit fails before creating anything when the project has no region",
+  Effect.fn(function* (stack: Test.ScratchStack) {
+    yield* stack.destroy();
+
+    const failure = yield* failureOf(
+      stack.deploy(
+        Effect.gen(function* () {
+          const project = yield* Prisma.Project("Project", { createDatabase: false });
+          const database = yield* Prisma.Database("Inherited", { project, region: "inherit" });
+          return { project, database };
+        }),
+      ),
+    );
+    expect(failure.text).toContain("has no default region and no default database region");
+
+    yield* stack.destroy();
+  }),
+  { tags: logicalIdTags, timeout: 180_000 },
+);

packages/alchemy/test/Prisma/ManagementLifecycle.test.ts

@@ -956,11 +956,16 @@ const apiDatabase = (
 const makeDatabaseCloud = () => {
   const databases = new Map<string, ApiDatabase>();
   const calls: Array<[string, unknown?]> = [];
+  const project = { defaultRegion: null as string | null };
   let nextId = 1;
   // The same in-memory cloud, served over the wire for the Database resource.
   const fake = makeFakeManagementApi((request) => {
     const segments = request.pathname.split("/").filter((s) => s.length > 0);
 
+    if (segments.length === 3 && segments[1] === "projects" && request.method === "GET") {
+      return data(toWireProject(apiProject(segments[2]!, "app", project.defaultRegion)));
+    }
+
     if (request.pathname === "/v1/databases" && request.method === "GET") {
       return page(Array.from(databases.values()).map(toWireDatabase));
     }
@@ -1048,7 +1053,7 @@ const makeDatabaseCloud = () => {
     return unhandled(request);
   });
 
-  return { fake, calls, databases };
+  return { fake, calls, databases, project };
 };
 
 const generatedDatabaseRecoveryCloud = makeDatabaseCloud();
@@ -1258,7 +1263,7 @@ const inheritedRegionCloud = makeDatabaseCloud();
 const inheritedRegion = Test.make({ providers: databaseLayer(inheritedRegionCloud.fake) });
 
 inheritedRegion.test.provider(
-  "Database region inherit is stable and follows the project default region",
+  "Database region inherit falls back to the default database region",
   (stack) =>
     Effect.gen(function* () {
       inheritedRegionCloud.databases.clear();