new setupcfg writer

src/codemodder/dependency_management/dependency_manager.py

@@ -8,6 +8,7 @@
 from codemodder.dependency_management.setup_py_writer import (
     SetupPyWriter,
 )
+from codemodder.dependency_management.setupcfg_writer import SetupCfgWriter
 
 from codemodder.project_analysis.file_parsers.package_store import (
     PackageStore,
@@ -43,4 +44,8 @@ def write(
                 return SetupPyWriter(
                     self.dependencies_store, self.parent_directory
                 ).write(dependencies, dry_run)
+            case FileType.SETUP_CFG:
+                return SetupCfgWriter(
+                    self.dependencies_store, self.parent_directory
+                ).write(dependencies, dry_run)
         return None

src/codemodder/dependency_management/setupcfg_writer.py

@@ -0,0 +1,124 @@
+import configparser
+
+from typing import Optional
+from codemodder.dependency import Dependency
+from codemodder.change import ChangeSet
+from codemodder.dependency_management.base_dependency_writer import DependencyWriter
+from codemodder.diff import create_diff_and_linenums
+from codemodder.logging import logger
+
+
+import re
+
+
+def find_leading_whitespace(s):
+    match = re.match(r"(\s+)", s)
+    if match:
+        return match.group(1)
+    return ""
+
+
+def added_line_nums_strategy(lines, i):
+    return lines[i]
+
+
+class SetupCfgWriter(DependencyWriter):
+    def add_to_file(
+        self, dependencies: list[Dependency], dry_run: bool = False
+    ) -> Optional[ChangeSet]:
+        config = configparser.ConfigParser()
+
+        try:
+            config.read(self.path)
+        except configparser.ParsingError:
+            logger.debug("Unable to parse setup.cfg file.")
+            return None
+
+        if "options" not in config or not (
+            defined_dependencies := config["options"].get("install_requires", "")
+        ):
+            logger.debug("Unable to add dependencies to setup.cfg file.")
+            return None
+
+        with open(self.path, "r", encoding="utf-8") as f:
+            original_lines = f.readlines()
+
+        new_lines = self.build_new_lines(
+            original_lines, defined_dependencies, dependencies
+        )
+        if not new_lines:
+            logger.debug("Unable to add dependencies to setup.cfg file.")
+            return None
+
+        if not dry_run:
+            try:
+                with open(self.path, "w", encoding="utf-8") as f:
+                    f.writelines(new_lines)
+            except Exception:
+                logger.debug("Unable to add dependencies to setup.cfg file.")
+                return None
+
+        diff, added_line_nums = create_diff_and_linenums(original_lines, new_lines)
+
+        changes = self.build_changes(
+            dependencies, added_line_nums_strategy, added_line_nums
+        )
+        return ChangeSet(
+            str(self.path.relative_to(self.parent_directory)),
+            diff,
+            changes=changes,
+        )
+
+    def build_new_lines(
+        self,
+        original_lines: list[str],
+        defined_dependencies: str,
+        dependencies_to_add: list[Dependency],
+    ) -> Optional[list[str]]:
+        """
+        configparser does not retain formatting or comment lines, so we have to build
+        the output newline manually.
+        """
+        clean_lines = list(map(lambda s: s.strip(), original_lines))
+
+        newline_separated = len(defined_dependencies.split("\n")) > 1
+        if newline_separated:
+            last_dep_line = defined_dependencies.split("\n")[-1]
+            dep_sep = "\n"
+        else:
+            # deps are in same line as install_requires key separated by commas
+            last_dep_line = [
+                line for line in clean_lines if line.endswith(defined_dependencies)
+            ][-1]
+            dep_sep = ","
+
+        try:
+            last_dep_idx = clean_lines.index(last_dep_line)
+        except ValueError:
+            # we were unable to find the last req line due to some formatting issue
+            logger.debug("Unable to add dependencies to setup.cfg file.")
+            return None
+
+        if newline_separated:
+            formatting = find_leading_whitespace(original_lines[last_dep_idx])
+            new_deps = [
+                f"{formatting}{dep.requirement}{dep_sep}" for dep in dependencies_to_add
+            ]
+            new_lines = (
+                original_lines[: last_dep_idx + 1]
+                + new_deps
+                + original_lines[last_dep_idx + 1 :]
+            )
+        else:
+            # new_deps added to existing deps line
+            new_dep = ",".join(
+                [f"{dep.requirement}{dep_sep}" for dep in dependencies_to_add]
+            )
+            new_dep_line = f"{original_lines[last_dep_idx].rstrip()}, {new_dep}\n"
+            new_lines = (
+                original_lines[:last_dep_idx]
+                + [new_dep_line]
+                + original_lines[last_dep_idx + 1 :]
+            )
+
+        return new_lines

src/codemodder/project_analysis/file_parsers/setup_cfg_file_parser.py

@@ -6,6 +6,7 @@
 import configparser
 
 from .base_parser import BaseParser
+from codemodder.logging import logger
 
 
 class SetupCfgParser(BaseParser):
@@ -15,13 +16,17 @@ def file_type(self):
 
     def _parse_file(self, file: Path) -> PackageStore | None:
         config = configparser.ConfigParser()
-        config.read(file)
+        try:
+            config.read(file)
+        except configparser.ParsingError:
+            logger.debug("Unable to parse setup.cfg file.")
+            return None
 
-        if not (options := config["options"]):
+        if "options" not in config:
             return None
 
-        dependency_lines = options.get("install_requires", "").split("\n")
-        python_requires = options.get("python_requires", "")
+        dependency_lines = config["options"].get("install_requires", "").split("\n")
+        python_requires = config["options"].get("python_requires", "")
 
         return PackageStore(
             type=self.file_type,

tests/dependency_management/test_pyproject_writer.py

@@ -169,6 +169,7 @@ def test_dont_add_existing_dependency(tmpdir):
             "libcst~=1.1.0",
             "pylint~=3.0.0",
             "PyYAML~=6.0.0",
+            "security~=1.2.0",
         ]
     """