pr: add GitHub approval upon success with --approve-pr

nixpkgs_review/cli/__init__.py

@@ -165,6 +165,11 @@ def common_flags() -> list[CommonFlag]:
             action="store_true",
             help="Only evaluate and build without executing nix-shell",
         ),
+        CommonFlag(
+            "--approve-pr",
+            action="store_true",
+            help="Approve PR on review success",
+        ),
         CommonFlag(
             "-p",
             "--package",

nixpkgs_review/cli/pr.py

@@ -63,7 +63,7 @@ def pr_command(args: argparse.Namespace) -> str:
         CheckoutOption.MERGE if args.checkout == "merge" else CheckoutOption.COMMIT
     )
 
-    if args.post_result:
+    if args.post_result or args.approve_pr:
         ensure_github_token(args.token)
     if args.system:
         warn("Warning: The `--system` is deprecated. Use `--systems` instead.")
@@ -119,7 +119,9 @@ def pr_command(args: argparse.Namespace) -> str:
         assert review is not None
 
         all_succeeded = all(
-            review.start_review(attrs, path, pr, args.post_result, args.print_result)
+            review.start_review(
+                attrs, path, pr, args.post_result, args.print_result, args.approve_pr
+            )
             for pr, path, attrs in contexts
         )
 

nixpkgs_review/github.py

@@ -9,7 +9,7 @@
 from pathlib import Path
 from typing import IO, Any, override
 
-from .utils import System
+from .utils import System, warn
 
 
 def pr_url(pr: int) -> str:
@@ -80,13 +80,24 @@ def comment_issue(self, pr: int, msg: str) -> Any:
             f"/repos/NixOS/nixpkgs/issues/{pr}/comments", data={"body": msg}
         )
 
-    def approve_pr(self, pr: int) -> Any:
-        "Approve a PR"
+    def approve_pr(self, pr: int, comment: str = "") -> Any:
+        "Approve a PR with an optional comment"
         print(f"Approving {pr_url(pr)}")
-        return self.post(
-            f"/repos/NixOS/nixpkgs/pulls/{pr}/reviews",
-            data={"event": "APPROVE"},
-        )
+        data = {"event": "APPROVE"}
+        if comment:
+            data["body"] = comment
+        try:
+            return self.post(
+                f"/repos/NixOS/nixpkgs/pulls/{pr}/reviews",
+                data=data,
+            )
+        except urllib.error.HTTPError as e:
+            if e.code == 422:
+                warn(
+                    "Sorry, unable to process request. You may have tried to approve your own PR, which is unsupported by GitHub"
+                )
+            else:
+                raise
 
     def merge_pr(self, pr: int) -> Any:
         "Merge a PR. Requires maintainer access to NixPkgs"

nixpkgs_review/review.py

@@ -391,6 +391,7 @@ def start_review(
         pr: int | None = None,
         post_result: bool | None = False,
         print_result: bool = False,
+        approve_pr: bool = False,
     ) -> bool:
         os.environ.pop("NIXPKGS_CONFIG", None)
         os.environ["NIXPKGS_REVIEW_ROOT"] = str(path)
@@ -409,9 +410,17 @@ def start_review(
         report.print_console(pr)
         report.write(path, pr)
 
+        success = report.succeeded()
+
         if pr and post_result:
             self.github_client.comment_issue(pr, report.markdown(pr))
 
+        if pr and approve_pr and success:
+            self.github_client.approve_pr(
+                pr,
+                "Approved automatically following the successful run of `nixpkgs-review`.",
+            )
+
         if print_result:
             print(report.markdown(pr))
 
@@ -428,7 +437,7 @@ def start_review(
                 self.sandbox,
             )
 
-        return report.succeeded()
+        return success
 
     def review_commit(
         self,
@@ -437,12 +446,14 @@ def review_commit(
         reviewed_commit: str | None,
         staged: bool = False,
         print_result: bool = False,
+        approve_pr: bool = False,
     ) -> None:
         branch_rev = fetch_refs(self.remote, branch)[0]
         self.start_review(
             self.build_commit(branch_rev, reviewed_commit, staged),
             path,
             print_result=print_result,
+            approve_pr=approve_pr,
         )