Add totals report

.flake8

@@ -0,0 +1,8 @@
+# This file is not used by anything in the repo.
+# It is here as a convenience to developers who use flake8 locally.
+
+[flake8]
+ignore =
+    E203  # whitespace before ':' - conflicts with black
+    E501  # line too long - black takes care of this for us
+    W503  # line break before binary operator - this is what black does

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Add `help` command to print out usage information.
+- Add `totals` command to quantify the errors recorded in a file.
 - Use GA version of Python 3.11 in test matrix.
 
 ## v0.1.3 [2022-09-07]

mypy_json_report.py

@@ -12,16 +12,64 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import argparse
 import json
+import pathlib
 import sys
 from collections import Counter, defaultdict
 from dataclasses import dataclass
-from typing import Counter as CounterType
-from typing import Dict, Iterator
+from typing import Counter as CounterType, Dict, Iterator
+
+from typing_extensions import Protocol
+
+
+def parser_command(args: object) -> None:
+    report_errors()
+
+
+class TotalsArgs(Protocol):
+    filepath: str
+
+
+def totals_command(args: TotalsArgs) -> None:
+    summarize_errors(filepath=args.filepath)
 
 
 def main() -> None:
-    print(produce_errors_report(sys.stdin))
+    parser = argparse.ArgumentParser()
+    subparsers = parser.add_subparsers(title="command")
+    # If no command is defined, default to the parser command.
+    # This preserves legacy behavior.
+    parser.set_defaults(func=parser_command)
+
+    parse_parser = subparsers.add_parser(
+        "parse", help="Transform Mypy output into JSON."
+    )
+    parse_parser.set_defaults(func=parser_command)
+
+    totals_parser = subparsers.add_parser(
+        "totals", help="Summarizes the errors in _file_ in JSON format."
+    )
+    totals_parser.add_argument("filepath", type=pathlib.Path)
+    totals_parser.set_defaults(func=totals_command)
+
+    args = sys.argv[1:]
+    parsed = parser.parse_args(args)
+    parsed.func(parsed)
+
+
+def report_errors() -> None:
+    errors = produce_errors_report(sys.stdin)
+    error_json = json.dumps(errors, sort_keys=True, indent=2)
+    print(error_json)
+
+
+def summarize_errors(*, filepath: str) -> None:
+    errors_json = pathlib.Path(filepath).read_text()
+    errors = json.loads(errors_json)
+    summary = produce_errors_summary(errors)
+    summary_json = json.dumps(summary, sort_keys=True)
+    print(summary_json)
 
 
 @dataclass(frozen=True)
@@ -30,12 +78,18 @@ class MypyError:
     message: str
 
 
-def produce_errors_report(input_lines: Iterator[str]) -> str:
+def produce_errors_summary(errors: Dict[str, Dict[str, int]]) -> Dict[str, int]:
+    total_errors = sum(sum(file_errors.values()) for file_errors in errors.values())
+    files_with_errors = len(errors.keys())
+    return {"files_with_errors": files_with_errors, "total_errors": total_errors}
+
+
+def produce_errors_report(input_lines: Iterator[str]) -> Dict[str, Dict[str, int]]:
     """Given lines from mypy's output, return a JSON summary of error frequencies by file."""
     errors = _extract_errors(input_lines)
     error_frequencies = _count_errors(errors)
     structured_errors = _structure_errors(error_frequencies)
-    return json.dumps(structured_errors, sort_keys=True, indent=2)
+    return structured_errors
 
 
 def _extract_errors(lines: Iterator[str]) -> Iterator[MypyError]:

pyproject.toml

@@ -38,3 +38,9 @@ mypy-json-report = "mypy_json_report:main"
 [build-system]
 requires = ["poetry-core>=1.0.0"]
 build-backend = "poetry.core.masonry.api"
+
+[tool.isort]
+combine_as_imports = true
+known_first_party = ["mypy_json_report"]
+lines_after_imports = 2
+profile = "black"

tests/test_mypy_json_report.py

@@ -1,7 +1,7 @@
-import json
 from io import StringIO
 
-from mypy_json_report import produce_errors_report
+from mypy_json_report import produce_errors_report, produce_errors_summary
+
 
 EXAMPLE_MYPY_STDOUT = """\
 mypy_json_report.py:8: error: Function is missing a return type annotation
@@ -10,12 +10,29 @@
 Found 2 errors in 1 file (checked 3 source files)"""
 
 
-def test_report() -> None:
+def test_errors_report() -> None:
     report = produce_errors_report(StringIO(EXAMPLE_MYPY_STDOUT))
 
-    assert json.loads(report) == {
+    assert report == {
         "mypy_json_report.py": {
             'Call to untyped function "main" in typed context': 1,
             "Function is missing a return type annotation": 1,
         }
     }
+
+
+def test_errors_summary() -> None:
+    errors = {
+        "file.py": {
+            'Call to untyped function "main" in typed context': 1,
+            "Function is missing a return type annotation": 2,
+        },
+        "another_file.py": {
+            'Call to untyped function "test" in typed context': 1,
+            "Function is missing a return type annotation": 1,
+        },
+    }
+
+    totals = produce_errors_summary(errors)
+
+    assert totals == {"files_with_errors": 2, "total_errors": 5}