fix: bump changelog for prerelease without commits

generate changelog for a new version without new commits when the current version is a prerelease. This matches current behaviour for bump command

commitizen/changelog.py

@@ -90,10 +90,12 @@ def generate_tree_from_commits(
     pat = re.compile(changelog_pattern)
     map_pat = re.compile(commit_parser, re.MULTILINE)
     body_map_pat = re.compile(commit_parser, re.MULTILINE | re.DOTALL)
+    current_tag: Optional[GitTag] = None
 
     # Check if the latest commit is not tagged
-    latest_commit = commits[0]
-    current_tag: Optional[GitTag] = get_commit_tag(latest_commit, tags)
+    if commits:
+        latest_commit = commits[0]
+        current_tag = get_commit_tag(latest_commit, tags)
 
     current_tag_name: str = unreleased_version or "Unreleased"
     current_tag_date: str = ""

commitizen/commands/changelog.py

@@ -3,6 +3,8 @@
 from operator import itemgetter
 from typing import Callable, Dict, List, Optional
 
+from packaging.version import parse
+
 from commitizen import bump, changelog, defaults, factory, git, out, version_types
 from commitizen.config import BaseConfig
 from commitizen.exceptions import (
@@ -36,6 +38,13 @@ def __init__(self, config: BaseConfig, args):
             "changelog_incremental"
         )
         self.dry_run = args["dry_run"]
+
+        self.current_version = (
+            args.get("current_version") or self.config.settings.get("version") or ""
+        )
+        self.current_version_instance = (
+            parse(self.current_version) if self.current_version else None
+        )
         self.unreleased_version = args["unreleased_version"]
         self.change_type_map = (
             self.config.settings.get("change_type_map") or self.cz.change_type_map
@@ -155,7 +164,10 @@ def __call__(self):
             )
 
         commits = git.get_commits(start=start_rev, end=end_rev, args="--topo-order")
-        if not commits:
+        if not commits and (
+            self.current_version_instance is None
+            or not self.current_version_instance.is_prerelease
+        ):
             raise NoCommitsFoundError("No commits found")
 
         tree = changelog.generate_tree_from_commits(

tests/commands/test_changelog_command.py

@@ -1,3 +1,4 @@
+import itertools
 import sys
 from datetime import datetime
 
@@ -660,6 +661,36 @@ def test_changelog_incremental_with_release_candidate_version(
     file_regression.check(out, extension=".md")
 
 
+@pytest.mark.parametrize(
+    "from_pre,to_pre", itertools.product(["alpha", "beta", "rc"], repeat=2)
+)
+@pytest.mark.usefixtures("tmp_commitizen_project")
+@pytest.mark.freeze_time("2021-06-11")
+def test_changelog_incremental_with_prerelease_version_to_prerelease_version(
+    mocker: MockFixture, changelog_path, file_regression, from_pre, to_pre
+):
+    with open(changelog_path, "w") as f:
+        f.write(KEEP_A_CHANGELOG)
+    create_file_and_commit("irrelevant commit")
+    git.tag("1.0.0", annotated=True)
+
+    create_file_and_commit("feat: add new output")
+    create_file_and_commit("fix: output glitch")
+
+    testargs = ["cz", "bump", "--changelog", "--prerelease", from_pre, "--yes"]
+    mocker.patch.object(sys, "argv", testargs)
+    cli.main()
+
+    testargs = ["cz", "bump", "--changelog", "--prerelease", to_pre, "--yes"]
+    mocker.patch.object(sys, "argv", testargs)
+    cli.main()
+
+    with open(changelog_path, "r") as f:
+        out = f.read()
+
+    file_regression.check(out, extension=".md")
+
+
 @pytest.mark.parametrize("test_input", ["rc", "alpha", "beta"])
 @pytest.mark.usefixtures("tmp_commitizen_project")
 def test_changelog_release_candidate_version_with_merge_prerelease(

tests/commands/test_changelog_command/test_changelog_incremental_with_prerelease_version_to_prerelease_version_alpha_alpha_.md

@@ -0,0 +1,32 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.2.0a1 (2021-06-11)
+
+## 0.2.0a0 (2021-06-11)
+
+### Feat
+
+- add new output
+
+### Fix
+
+- output glitch
+
+## [1.0.0] - 2017-06-20
+### Added
+- New visual identity by [@tylerfortune8](https://github.com/tylerfortune8).
+- Version navigation.
+
+### Changed
+- Start using "changelog" over "change log" since it's the common usage.
+
+### Removed
+- Section about "changelog" vs "CHANGELOG".
+
+## [0.3.0] - 2015-12-03
+### Added
+- RU translation from [@aishek](https://github.com/aishek).

tests/commands/test_changelog_command/test_changelog_incremental_with_prerelease_version_to_prerelease_version_alpha_beta_.md

@@ -0,0 +1,32 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.2.0b0 (2021-06-11)
+
+## 0.2.0a0 (2021-06-11)
+
+### Feat
+
+- add new output
+
+### Fix
+
+- output glitch
+
+## [1.0.0] - 2017-06-20
+### Added
+- New visual identity by [@tylerfortune8](https://github.com/tylerfortune8).
+- Version navigation.
+
+### Changed
+- Start using "changelog" over "change log" since it's the common usage.
+
+### Removed
+- Section about "changelog" vs "CHANGELOG".
+
+## [0.3.0] - 2015-12-03
+### Added
+- RU translation from [@aishek](https://github.com/aishek).

tests/commands/test_changelog_command/test_changelog_incremental_with_prerelease_version_to_prerelease_version_alpha_rc_.md

@@ -0,0 +1,32 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.2.0rc0 (2021-06-11)
+
+## 0.2.0a0 (2021-06-11)
+
+### Feat
+
+- add new output
+
+### Fix
+
+- output glitch
+
+## [1.0.0] - 2017-06-20
+### Added
+- New visual identity by [@tylerfortune8](https://github.com/tylerfortune8).
+- Version navigation.
+
+### Changed
+- Start using "changelog" over "change log" since it's the common usage.
+
+### Removed
+- Section about "changelog" vs "CHANGELOG".
+
+## [0.3.0] - 2015-12-03
+### Added
+- RU translation from [@aishek](https://github.com/aishek).

tests/commands/test_changelog_command/test_changelog_incremental_with_prerelease_version_to_prerelease_version_beta_alpha_.md

@@ -0,0 +1,32 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.2.0a0 (2021-06-11)
+
+## 0.2.0b0 (2021-06-11)
+
+### Feat
+
+- add new output
+
+### Fix
+
+- output glitch
+
+## [1.0.0] - 2017-06-20
+### Added
+- New visual identity by [@tylerfortune8](https://github.com/tylerfortune8).
+- Version navigation.
+
+### Changed
+- Start using "changelog" over "change log" since it's the common usage.
+
+### Removed
+- Section about "changelog" vs "CHANGELOG".
+
+## [0.3.0] - 2015-12-03
+### Added
+- RU translation from [@aishek](https://github.com/aishek).

tests/commands/test_changelog_command/test_changelog_incremental_with_prerelease_version_to_prerelease_version_beta_beta_.md

@@ -0,0 +1,32 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.2.0b1 (2021-06-11)
+
+## 0.2.0b0 (2021-06-11)
+
+### Feat
+
+- add new output
+
+### Fix
+
+- output glitch
+
+## [1.0.0] - 2017-06-20
+### Added
+- New visual identity by [@tylerfortune8](https://github.com/tylerfortune8).
+- Version navigation.
+
+### Changed
+- Start using "changelog" over "change log" since it's the common usage.
+
+### Removed
+- Section about "changelog" vs "CHANGELOG".
+
+## [0.3.0] - 2015-12-03
+### Added
+- RU translation from [@aishek](https://github.com/aishek).

tests/commands/test_changelog_command/test_changelog_incremental_with_prerelease_version_to_prerelease_version_beta_rc_.md

@@ -0,0 +1,32 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.2.0rc0 (2021-06-11)
+
+## 0.2.0b0 (2021-06-11)
+
+### Feat
+
+- add new output
+
+### Fix
+
+- output glitch
+
+## [1.0.0] - 2017-06-20
+### Added
+- New visual identity by [@tylerfortune8](https://github.com/tylerfortune8).
+- Version navigation.
+
+### Changed
+- Start using "changelog" over "change log" since it's the common usage.
+
+### Removed
+- Section about "changelog" vs "CHANGELOG".
+
+## [0.3.0] - 2015-12-03
+### Added
+- RU translation from [@aishek](https://github.com/aishek).

tests/commands/test_changelog_command/test_changelog_incremental_with_prerelease_version_to_prerelease_version_rc_alpha_.md

@@ -0,0 +1,32 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.2.0a0 (2021-06-11)
+
+## 0.2.0rc0 (2021-06-11)
+
+### Feat
+
+- add new output
+
+### Fix
+
+- output glitch
+
+## [1.0.0] - 2017-06-20
+### Added
+- New visual identity by [@tylerfortune8](https://github.com/tylerfortune8).
+- Version navigation.
+
+### Changed
+- Start using "changelog" over "change log" since it's the common usage.
+
+### Removed
+- Section about "changelog" vs "CHANGELOG".
+
+## [0.3.0] - 2015-12-03
+### Added
+- RU translation from [@aishek](https://github.com/aishek).

tests/commands/test_changelog_command/test_changelog_incremental_with_prerelease_version_to_prerelease_version_rc_beta_.md

@@ -0,0 +1,32 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.2.0b0 (2021-06-11)
+
+## 0.2.0rc0 (2021-06-11)
+
+### Feat
+
+- add new output
+
+### Fix
+
+- output glitch
+
+## [1.0.0] - 2017-06-20
+### Added
+- New visual identity by [@tylerfortune8](https://github.com/tylerfortune8).
+- Version navigation.
+
+### Changed
+- Start using "changelog" over "change log" since it's the common usage.
+
+### Removed
+- Section about "changelog" vs "CHANGELOG".
+
+## [0.3.0] - 2015-12-03
+### Added
+- RU translation from [@aishek](https://github.com/aishek).

tests/commands/test_changelog_command/test_changelog_incremental_with_prerelease_version_to_prerelease_version_rc_rc_.md

@@ -0,0 +1,32 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.2.0rc1 (2021-06-11)
+
+## 0.2.0rc0 (2021-06-11)
+
+### Feat
+
+- add new output
+
+### Fix
+
+- output glitch
+
+## [1.0.0] - 2017-06-20
+### Added
+- New visual identity by [@tylerfortune8](https://github.com/tylerfortune8).
+- Version navigation.
+
+### Changed
+- Start using "changelog" over "change log" since it's the common usage.
+
+### Removed
+- Section about "changelog" vs "CHANGELOG".
+
+## [0.3.0] - 2015-12-03
+### Added
+- RU translation from [@aishek](https://github.com/aishek).