fix(gitlab): merge messages drop agent credits

packages/source-control-gitlab/src/server/GitLabPullRequestCli.test.ts

@@ -437,6 +437,164 @@ layer("GitLabPullRequestCli.layer", (it) => {
       }),
   );
 
+  it.effect.each([
+    {
+      mergeMethod: "squash",
+      squashOnMerge: false,
+      squash: "Add thing\n\nCo-authored-by: Codex <noreply@openai.com>",
+      flags: [
+        "--squash",
+        "--sha",
+        "head",
+        "--message",
+        "Merge branch 'feature' into 'main'\n\nAdd thing\n\nCo-authored-by: Ada <ada@example.com>",
+        "--squash-message",
+        "Add thing",
+      ],
+    },
+    {
+      mergeMethod: "merge",
+      squashOnMerge: false,
+      squash: "Add thing\n\nCo-authored-by: Codex <noreply@openai.com>",
+      flags: [
+        "--sha",
+        "head",
+        "--message",
+        "Merge branch 'feature' into 'main'\n\nAdd thing\n\nCo-authored-by: Ada <ada@example.com>",
+      ],
+    },
+    {
+      mergeMethod: "merge",
+      squashOnMerge: true,
+      squash: "Add thing\n\nCo-authored-by: Codex <noreply@openai.com>",
+      flags: [
+        "--sha",
+        "head",
+        "--message",
+        "Merge branch 'feature' into 'main'\n\nAdd thing\n\nCo-authored-by: Ada <ada@example.com>",
+        "--squash",
+        "--squash-message",
+        "Add thing",
+      ],
+    },
+    {
+      mergeMethod: "squash",
+      squashOnMerge: false,
+      squash: "Co-authored-by: Codex <noreply@openai.com>",
+      flags: [
+        "--squash",
+        "--sha",
+        "head",
+        "--message",
+        "Merge branch 'feature' into 'main'\n\nAdd thing\n\nCo-authored-by: Ada <ada@example.com>",
+        "--squash-message",
+        "Add thing",
+      ],
+    },
+  ] as const)(
+    "removes agent credits from GitLab's default messages for a $mergeMethod (squash on merge: $squashOnMerge)",
+    ({ mergeMethod, squashOnMerge, squash, flags }) =>
+      Effect.gen(function* () {
+        const credits =
+          "Co-authored-by: Ada <ada@example.com>\nCo-authored-by: Claude <noreply@anthropic.com>";
+        mockedExecute.mockImplementation(({ args }) =>
+          Effect.succeed(
+            output(
+              args[1] === "graphql"
+                ? JSON.stringify({
+                    data: {
+                      project: {
+                        mergeRequest: {
+                          title: "Add thing",
+                          squashOnMerge,
+                          defaultMergeCommitMessage: `Merge branch 'feature' into 'main'\n\nAdd thing\n\n${credits}`,
+                          defaultSquashCommitMessage: squash,
+                        },
+                      },
+                    },
+                  })
+                : args[0] === "api"
+                  ? mergeRequestJson({
+                      diff_refs: { base_sha: "base", head_sha: "head", start_sha: "start" },
+                    })
+                  : "",
+            ),
+          ),
+        );
+        const cli = yield* GitLabPullRequestCli.GitLabPullRequestCli;
+
+        yield* cli.runMergeRequestAction({
+          cwd: "/w",
+          repository: "acme/web",
+          number: 7,
+          action: "merge",
+          mergeMethod,
+          removeAgentCreditsOnMerge: true,
+        });
+
+        expect(mockedExecute.mock.calls.at(-1)?.[0].args).toEqual([
+          "mr",
+          "merge",
+          "7",
+          "--repo",
+          "acme/web",
+          "--auto-merge=false",
+          "--yes",
+          ...flags,
+        ]);
+      }),
+  );
+
+  it.effect("keeps GitLab's merge messages when they carry no agent credits", () =>
+    Effect.gen(function* () {
+      mockedExecute.mockImplementation(({ args }) =>
+        Effect.succeed(
+          output(
+            args[1] === "graphql"
+              ? JSON.stringify({
+                  data: {
+                    project: {
+                      mergeRequest: {
+                        defaultMergeCommitMessage: "Merge branch 'feature' into 'main'",
+                        defaultSquashCommitMessage: "Add thing",
+                      },
+                    },
+                  },
+                })
+              : args[0] === "api"
+                ? mergeRequestJson({
+                    diff_refs: { base_sha: "base", head_sha: "head", start_sha: "start" },
+                  })
+                : "",
+          ),
+        ),
+      );
+      const cli = yield* GitLabPullRequestCli.GitLabPullRequestCli;
+
+      yield* cli.runMergeRequestAction({
+        cwd: "/w",
+        repository: "acme/web",
+        number: 7,
+        action: "enable-auto-merge",
+        mergeMethod: "squash",
+        removeAgentCreditsOnMerge: true,
+      });
+
+      expect(mockedExecute.mock.calls.at(-1)?.[0].args).toEqual([
+        "mr",
+        "merge",
+        "7",
+        "--repo",
+        "acme/web",
+        "--auto-merge=true",
+        "--yes",
+        "--squash",
+        "--sha",
+        "head",
+      ]);
+    }),
+  );
+
   it.effect.each(["merge", "enable-auto-merge"] as const)(
     "does not run %s when GitLab has no diff revisions",
     (action) =>

packages/source-control-gitlab/src/server/GitLabPullRequestCli.ts

@@ -1,3 +1,4 @@
+import { removeAgentCredits } from "@t3tools/source-control-core/server/mergeMessage";
 import { isCommitSha } from "@t3tools/source-control-core/server/pullRequestUtils";
 import * as Context from "effect/Context";
 import * as Effect from "effect/Effect";
@@ -35,6 +36,7 @@ import {
   decodeCommitsJson,
   decodeDiffRefsJson,
   decodeDiscussionsJson,
+  decodeMergeMessagesJson,
   decodeMergeRequestDetailJson,
   decodeMergeRequestDiffsJson,
   decodeMergeRequestChangesJson,
@@ -51,6 +53,7 @@ import {
   decodeTriggerJobChecksJson,
   decodeViewerJson,
   gitLabAwardName,
+  MERGE_MESSAGES_GRAPHQL_QUERY,
   MERGE_REQUEST_FILE_STATS_GRAPHQL_QUERY,
   MERGE_REQUEST_STATS_GRAPHQL_QUERY,
   REPOSITORY_BLOBS_GRAPHQL_QUERY,
@@ -386,6 +389,7 @@ export class GitLabPullRequestCli extends Context.Service<
       readonly number: number;
       readonly action: PullRequestAction;
       readonly mergeMethod?: PullRequestMergeMethod;
+      readonly removeAgentCreditsOnMerge?: boolean;
     }) => Effect.Effect<void, GitLabPullRequestCliError>;
 
     readonly updateMergeRequest: (input: {
@@ -1672,6 +1676,32 @@ export const make = Effect.gen(function* () {
           }
           const refs = yield* getDiffRefs(input);
           flags.push("--sha", refs.headSha);
+          if (input.removeAgentCreditsOnMerge === true) {
+            // Read after the SHA guard, so a push since then fails the merge instead of
+            // merging commits whose credits these messages don't cover.
+            const messages = yield* graphqlRead({
+              cwd: input.cwd,
+              host: input.host,
+              operation: "getMergeMessages",
+              query: MERGE_MESSAGES_GRAPHQL_QUERY,
+              variables: { fullPath: input.repository, iid: String(input.number) },
+              decode: decodeMergeMessagesJson,
+            });
+            // glab drops an empty message, which would bring the credits back.
+            const clean = (message: string) => {
+              const cleaned = removeAgentCredits(message);
+              return cleaned.trim() === "" ? (messages.title ?? message) : cleaned;
+            };
+            const merge = messages.merge === null ? null : clean(messages.merge);
+            if (merge !== null && merge !== messages.merge) flags.push("--message", merge);
+            const squashes = input.mergeMethod === "squash" || messages.squashOnMerge;
+            const squash = messages.squash === null || !squashes ? null : clean(messages.squash);
+            if (squash !== null && squash !== messages.squash) {
+              // glab takes a squash message only alongside --squash, which changes nothing here.
+              if (!flags.includes("--squash")) flags.push("--squash");
+              flags.push("--squash-message", squash);
+            }
+          }
         }
         yield* executeMr(subcommand!, ...flags);
       },

packages/source-control-gitlab/src/server/GitLabPullRequestProvider.ts

@@ -1,3 +1,4 @@
+import { removeAgentCredits } from "@t3tools/source-control-core/server/mergeMessage";
 import { SourceControlProviderKind } from "@t3tools/contracts";
 import * as Cache from "effect/Cache";
 import * as Duration from "effect/Duration";
@@ -221,6 +222,7 @@ export const make = Effect.gen(function* () {
   const provider: PullRequestProviderApi = {
     kind: SourceControlProviderKind.make("gitlab"),
     capabilities: CAPABILITIES,
+    mergeMessageRewrite: removeAgentCredits,
     unavailableRequirement: UNAVAILABLE_REQUIREMENT,
 
     getViewer: (input) => cli.getViewerUsername(input).pipe(Effect.mapError(fail("getViewer"))),
@@ -441,6 +443,7 @@ export const make = Effect.gen(function* () {
           number: input.number,
           action: input.action,
           ...(input.mergeMethod === undefined ? {} : { mergeMethod: input.mergeMethod }),
+          ...(input.removeAgentCreditsOnMerge === true ? { removeAgentCreditsOnMerge: true } : {}),
         })
         .pipe(Effect.mapError(fail("runAction"))),
     ),

packages/source-control-gitlab/src/server/gitLabMergeRequestJson.test.ts

@@ -5,6 +5,7 @@ import {
   decodeAwardEmojiJson,
   decodeRepositoryBlobsJson,
   decodeCommitsJson,
+  decodeMergeMessagesJson,
   decodeMergeRequestDetailJson,
   decodeMergeRequestDiffsJson,
   decodeMergeRequestListJson,
@@ -790,3 +791,18 @@ describe("decodeMergeRequestStatsJson", () => {
     expect(read(2).truncated).toBe(true);
   });
 });
+
+describe("decodeMergeMessagesJson", () => {
+  it("fails a partial response instead of reading errored fields as absent templates", () => {
+    const decoded = decodeMergeMessagesJson(
+      JSON.stringify({
+        errors: [{ message: "Internal server error", path: ["project", "mergeRequest"] }],
+        data: {
+          project: { mergeRequest: { title: "Add thing", defaultMergeCommitMessage: null } },
+        },
+      }),
+    );
+
+    expect(Result.isFailure(decoded)).toBe(true);
+  });
+});

packages/source-control-gitlab/src/server/gitLabMergeRequestJson.ts

@@ -997,6 +997,56 @@ export function decodeRepositoryBlobsJson(
   return Result.succeed(blobs);
 }
 
+export const MERGE_MESSAGES_GRAPHQL_QUERY = `query($fullPath: ID!, $iid: String!) {
+  project(fullPath: $fullPath) {
+    mergeRequest(iid: $iid) { title squashOnMerge defaultMergeCommitMessage defaultSquashCommitMessage }
+  }
+}`;
+
+const RawMergeMessagesSchema = Schema.Struct({
+  // A field that errored reads as null, which must not pass for an absent template.
+  errors: Schema.optionalKey(Schema.Never),
+  data: Schema.Struct({
+    project: Schema.NullOr(
+      Schema.Struct({
+        mergeRequest: Schema.NullOr(
+          Schema.Struct({
+            title: Schema.optional(Schema.NullOr(Schema.String)),
+            squashOnMerge: Schema.optional(Schema.NullOr(Schema.Boolean)),
+            defaultMergeCommitMessage: Schema.optional(Schema.NullOr(Schema.String)),
+            defaultSquashCommitMessage: Schema.optional(Schema.NullOr(Schema.String)),
+          }),
+        ),
+      }),
+    ),
+  }),
+});
+
+const decodeMergeMessages = decodeJsonResult(RawMergeMessagesSchema);
+
+export interface GitLabMergeMessages {
+  readonly title: string | null;
+  readonly merge: string | null;
+  readonly squash: string | null;
+  /** GitLab squashes when the project always does or the merge request asks to. */
+  readonly squashOnMerge: boolean;
+}
+
+/** The messages GitLab would write from the project's merge and squash templates. */
+export function decodeMergeMessagesJson(
+  raw: string,
+): Result.Result<GitLabMergeMessages, DecodeFailure> {
+  return Result.map(decodeMergeMessages(raw), (decoded) => {
+    const mergeRequest = decoded.data.project?.mergeRequest;
+    return {
+      title: mergeRequest?.title ?? null,
+      merge: mergeRequest?.defaultMergeCommitMessage ?? null,
+      squash: mergeRequest?.defaultSquashCommitMessage ?? null,
+      squashOnMerge: mergeRequest?.squashOnMerge === true,
+    };
+  });
+}
+
 export const REVIEW_DECISIONS_GRAPHQL_QUERY = `query($fullPath: ID!, $iids: [String!]) {
   metadata { enterprise }
   project(fullPath: $fullPath) {