Add Python Black formatter

shell.nix

@@ -33,6 +33,7 @@ in
 
     (pkgs.python3.withPackages (ps: [
       ps.pytest
+      ps.black
     ]))
 
   ];

tests/test_eval.py

@@ -30,10 +30,10 @@ def common_test(extra_args: List[str]) -> None:
         assert built_job["name"] == "job1"
         assert built_job["outputs"]["out"].startswith("/nix/store")
         assert built_job["drvPath"].endswith(".drv")
-        assert built_job["meta"]['broken'] is False
+        assert built_job["meta"]["broken"] is False
 
         dotted_job = results[1]
-        assert dotted_job["attr"] == "\"dotted.attr\""
+        assert dotted_job["attr"] == '"dotted.attr"'
         assert dotted_job["attrPath"] == ["dotted.attr"]
 
         recurse_drv = results[2]
@@ -46,7 +46,7 @@ def common_test(extra_args: List[str]) -> None:
         substituted_job = results[4]
         assert substituted_job["attr"] == "substitutedJob"
         assert substituted_job["name"].startswith("hello-")
-        assert substituted_job["meta"]['broken'] is False
+        assert substituted_job["meta"]["broken"] is False
 
 
 def test_flake() -> None:

treefmt.toml

@@ -15,3 +15,7 @@ includes = ["*.nix"]
 command = "prettier"
 options = ["--write"]
 includes = ["*.toml"]
+
+[formatter.python]
+command = "black"
+includes = ["*.py"]