Feature/722 nox session check and compare to file

doc/changes/unreleased.md

@@ -5,3 +5,7 @@
 ## Bugfix
 
 * #840: Added `export` plugin installation within `dependency-update.yml`
+
+## Feature
+
+* #722: Added check in `workflow:generate` to compare the generated and existing content before writing out

exasol/toolbox/util/workflows/workflow.py

@@ -1,3 +1,4 @@
+import difflib
 from collections.abc import Mapping
 from pathlib import Path
 from typing import (
@@ -41,38 +42,62 @@
 class Workflow(BaseModel):
     model_config = ConfigDict(frozen=True, arbitrary_types_allowed=True)
 
+    template_path: Path
+    output_path: Path
     content: str
 
     @classmethod
     def load_from_template(
         cls,
-        file_path: Path,
+        template_path: Path,
+        output_directory: Path,
         github_template_dict: dict[str, Any],
         patch_yaml: WorkflowCommentedMap | None = None,
     ):
-        with bound_contextvars(template_file_name=file_path.name):
-            logger.debug("Load workflow template: %s", file_path.name)
+        with bound_contextvars(template_file_name=template_path.name):
+            logger.debug("Load workflow template: %s", template_path.name)
 
-            if not file_path.exists():
-                raise FileNotFoundError(file_path)
+            if not template_path.exists():
+                raise FileNotFoundError(template_path)
 
             try:
                 workflow_renderer = WorkflowRenderer(
                     github_template_dict=github_template_dict,
-                    file_path=file_path,
+                    file_path=template_path,
                     patch_yaml=patch_yaml,
                 )
-                workflow = workflow_renderer.render()
-                return cls(content=workflow)
+                return cls(
+                    template_path=template_path,
+                    output_path=output_directory / template_path.name,
+                    content=workflow_renderer.render(),
+                )
             except (YamlError, YamlKeyError) as ex:
                 raise ex
             except Exception as ex:
                 # Wrap all other "non-special" exceptions
-                raise ValueError(f"Error rendering file: {file_path}") from ex
+                raise ValueError(f"Error rendering file: {template_path}") from ex
+
+    def compare_to_file(self) -> str:
+        existing_content = (
+            self.output_path.read_text().strip() if self.output_path.exists() else ""
+        )
+        generated_content = self.content.strip()
+
+        diff = difflib.unified_diff(
+            existing_content.splitlines(),
+            generated_content.splitlines(),
+            fromfile=f"existing: {self.output_path.name}",
+            tofile="generated",
+            lineterm="",
+        )
+        return "\n".join(diff)
 
-    def write_to_file(self, file_path: Path) -> None:
-        logger.info("Write workflow file %s", file_path.name)
-        file_path.write_text(self.content + "\n")
+    def write_to_file(self) -> None:
+        if self.compare_to_file() == "":
+            logger.debug("Skip up-to-date workflow file %s", self.output_path.name)
+            return
+        logger.info("Write workflow file %s", self.output_path.name)
+        self.output_path.write_text(self.content + "\n")
 
 
 def _select_workflow_template(workflow_name: WorkflowChoice) -> Mapping[str, Path]:
@@ -119,12 +144,12 @@ def update_workflow(workflow_choice: WorkflowChoice, config: BaseConfig) -> None
 
         try:
             workflow = Workflow.load_from_template(
-                file_path=workflow_dict[workflow_name],
+                template_path=workflow_dict[workflow_name],
+                output_directory=config.github_workflow_directory,
                 github_template_dict=config.github_template_dict,
                 patch_yaml=patch_yaml,
             )
-            file_path = config.github_workflow_directory / f"{workflow_name}.yml"
-            workflow.write_to_file(file_path=file_path)
+            workflow.write_to_file()
         except YamlKeyError as ex:
             raise InvalidWorkflowPatcherEntryError(
                 file_path=config.github_workflow_patcher_yaml, entry=ex.entry  # type: ignore

test/unit/util/workflows/workflow_test.py

@@ -1,4 +1,5 @@
 from inspect import cleandoc
+from pathlib import Path
 from unittest.mock import patch
 
 import pytest
@@ -47,23 +48,78 @@ def test_works_as_expected(tmp_path, project_config):
         input_file_path.write_text(content)
 
         workflow = Workflow.load_from_template(
-            file_path=input_file_path,
+            template_path=input_file_path,
+            output_directory=tmp_path,
             github_template_dict=project_config.github_template_dict,
         )
         output_file_path = tmp_path / f"{input_file_path.name}"
-        workflow.write_to_file(file_path=output_file_path)
+        assert workflow.template_path == input_file_path
+        assert workflow.output_path == output_file_path
+        workflow.write_to_file()
 
         assert output_file_path.read_text() == cleandoc(expected_yaml) + "\n"
 
+    @staticmethod
+    def test_compare_to_file_accepts_matching_content(tmp_path):
+        content = "line 1\nline 2"
+        file_path = tmp_path / "workflow.yml"
+        file_path.write_text(f"\n{content}\n")
+
+        workflow = Workflow(
+            template_path=file_path,
+            output_path=file_path,
+            content=f"\n{content}\n",
+        )
+
+        assert workflow.compare_to_file() == ""
+
+    @staticmethod
+    def test_compare_to_file_reports_diff(tmp_path):
+        file_path = tmp_path / "workflow.yml"
+        file_path.write_text("line 1\nline 3\n")
+        workflow = Workflow(
+            template_path=file_path,
+            output_path=file_path,
+            content="line 1\nline 2",
+        )
+
+        diff = workflow.compare_to_file()
+
+        assert diff == (
+            f"--- existing: {file_path.name}\n"
+            "+++ generated\n"
+            "@@ -1,2 +1,2 @@\n"
+            " line 1\n"
+            "-line 3\n"
+            "+line 2"
+        )
+
+    @staticmethod
+    def test_write_to_file_skips_up_to_date_file(tmp_path):
+        file_path = tmp_path / "workflow.yml"
+        file_path.write_text("line 1\nline 2\n")
+        workflow = Workflow(
+            template_path=file_path,
+            output_path=file_path,
+            content="line 1\nline 2",
+        )
+
+        with patch.object(Path, "write_text") as write_text:
+            workflow.write_to_file()
+
+        write_text.assert_not_called()
+        assert file_path.read_text() == "line 1\nline 2\n"
+
     @staticmethod
     @pytest.mark.parametrize("template_path", WORKFLOW_TEMPLATE_OPTIONS.values())
     def test_works_for_all_templates(tmp_path, project_config, template_path):
         workflow = Workflow.load_from_template(
-            file_path=template_path,
+            template_path=template_path,
+            output_directory=tmp_path,
             github_template_dict=project_config.github_template_dict,
         )
         file_path = tmp_path / f"{template_path.name}"
-        workflow.write_to_file(file_path=file_path)
+        workflow.write_to_file()
 
         assert file_path.read_text() != ""
 
@@ -72,7 +128,8 @@ def test_fails_when_yaml_does_not_exist(tmp_path, project_config):
         file_path = tmp_path / "test.yaml"
         with pytest.raises(FileNotFoundError, match="test.yaml"):
             Workflow.load_from_template(
-                file_path=file_path,
+                template_path=file_path,
+                output_directory=tmp_path,
                 github_template_dict=project_config.github_template_dict,
             )
 
@@ -89,7 +146,8 @@ def test_raises_custom_exceptions(tmp_path, project_config, raised_exc):
         ):
             with pytest.raises(raised_exc):
                 Workflow.load_from_template(
-                    file_path=file_path,
+                    template_path=file_path,
+                    output_directory=tmp_path,
                     github_template_dict=project_config.github_template_dict,
                 )
 
@@ -103,7 +161,8 @@ def test_other_exceptions_raised_as_valuerror(tmp_path, project_config):
         ):
             with pytest.raises(ValueError):
                 Workflow.load_from_template(
-                    file_path=file_path,
+                    template_path=file_path,
+                    output_directory=tmp_path,
                     github_template_dict=project_config.github_template_dict,
                 )