feat: add an argument to limit the length of commit message

commitizen/cli.py

@@ -154,6 +154,12 @@ def __call__(
                         "action": "store_true",
                         "help": "Tell the command to automatically stage files that have been modified and deleted, but new files you have not told Git about are not affected.",
                     },
+                    {
+                        "name": ["-l", "--message-length-limit"],
+                        "type": int,
+                        "default": 0,
+                        "help": "length limit of the commit message; 0 for no limit",
+                    },
                 ],
             },
             {

commitizen/commands/commit.py

@@ -12,6 +12,7 @@
 from commitizen.cz.utils import get_backup_file_path
 from commitizen.exceptions import (
     CommitError,
+    CommitMessageLengthExceededError,
     CustomError,
     DryRunExit,
     NoAnswersError,
@@ -61,7 +62,16 @@ def prompt_commit_questions(self) -> str:
 
         if not answers:
             raise NoAnswersError()
-        return cz.message(answers)
+
+        message = cz.message(answers)
+        message_len = len(message.partition("\n")[0].strip())
+        message_length_limit: int = self.arguments.get("message_length_limit", 0)
+        if message_length_limit > 0 and message_len > message_length_limit:
+            raise CommitMessageLengthExceededError(
+                f"Length of commit message exceeds limit ({message_len}/{message_length_limit})"
+            )
+
+        return message
 
     def __call__(self):
         dry_run: bool = self.arguments.get("dry_run")

commitizen/cz/jira/jira.py

@@ -44,7 +44,7 @@ def questions(self) -> Questions:
         ]
         return questions
 
-    def message(self, answers) -> str:
+    def message(self, answers: dict) -> str:
         return " ".join(
             filter(
                 bool,

commitizen/exceptions.py

@@ -36,6 +36,7 @@ class ExitCode(enum.IntEnum):
     CHANGELOG_FORMAT_UNKNOWN = 29
     CONFIG_FILE_NOT_FOUND = 30
     CONFIG_FILE_IS_EMPTY = 31
+    COMMIT_MESSAGE_LENGTH_LIMIT_EXCEEDED = 32
 
 
 class CommitizenException(Exception):
@@ -201,3 +202,8 @@ class ConfigFileNotFound(CommitizenException):
 class ConfigFileIsEmpty(CommitizenException):
     exit_code = ExitCode.CONFIG_FILE_IS_EMPTY
     message = "Config file is empty, please check your file path again."
+
+
+class CommitMessageLengthExceededError(CommitizenException):
+    exit_code = ExitCode.COMMIT_MESSAGE_LENGTH_LIMIT_EXCEEDED
+    message = "Length of commit message exceeds the given limit."

docs/commit.md

@@ -36,3 +36,14 @@ You can use `cz commit --retry` to reuse the last commit message when the previo
 To automatically retry when running `cz commit`, you can set the `retry_after_failure`
 configuration option to `true`. Running `cz commit --no-retry` makes commitizen ignore `retry_after_failure`, forcing
 a new commit message to be prompted.
+
+### Commit message length limit
+
+The argument `-l` (or `--message-length-limit`) followed by a positive number can limit the length of commit messages.
+An exception would be raised when the message length exceeds the limit.
+For example, `cz commit -l 72` will limit the length of commit messages to 72 characters.
+By default the limit is set to 0, which means no limit on the length.
+
+**Note that the limit applies only to the first line of the message.**
+Specifically, for `ConventionalCommitsCz` the length only counts from the type of change to the subject,
+while the body and the footer are not counted.

tests/commands/test_commit_command.py

@@ -9,6 +9,7 @@
 from commitizen.cz.utils import get_backup_file_path
 from commitizen.exceptions import (
     CommitError,
+    CommitMessageLengthExceededError,
     CustomError,
     DryRunExit,
     NoAnswersError,
@@ -379,3 +380,29 @@ def test_commit_command_with_extra_args(config, mocker: MockFixture):
     commands.Commit(config, {"extra_cli_args": "-- -extra-args1 -extra-arg2"})()
     commit_mock.assert_called_once_with(ANY, args="-- -extra-args1 -extra-arg2")
     success_mock.assert_called_once()
+
+
+@pytest.mark.usefixtures("staging_is_clean")
+def test_commit_command_with_message_length_limit(config, mocker: MockFixture):
+    prompt_mock = mocker.patch("questionary.prompt")
+    prefix = "feat"
+    subject = "random subject"
+    message_length = len(prefix) + len(": ") + len(subject)
+    prompt_mock.return_value = {
+        "prefix": prefix,
+        "subject": subject,
+        "scope": "",
+        "is_breaking_change": False,
+        "body": "random body",
+        "footer": "random footer",
+    }
+
+    commit_mock = mocker.patch("commitizen.git.commit")
+    commit_mock.return_value = cmd.Command("success", "", b"", b"", 0)
+    success_mock = mocker.patch("commitizen.out.success")
+
+    commands.Commit(config, {"message_length_limit": message_length})()
+    success_mock.assert_called_once()
+
+    with pytest.raises(CommitMessageLengthExceededError):
+        commands.Commit(config, {"message_length_limit": message_length - 1})()

tests/test_cz_base.py

@@ -7,7 +7,7 @@ class DummyCz(BaseCommitizen):
     def questions(self):
         return [{"type": "input", "name": "commit", "message": "Initial commit:\n"}]
 
-    def message(self, answers):
+    def message(self, answers: dict):
         return answers["commit"]