Fix MyPy type errors in comparator and walker

- Add explicit type annotation for children list in walker.py (list[DirInfo | FileInfo])
- Add explicit type annotations for va/vb in sort.py comparator (float | str)
- Add type: ignore[operator] comments for safe comparisons with union types

The code uses isinstance checks to safely narrow types at runtime before comparisons,
but MyPy cannot infer this narrowing across union types in all cases.

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

Author: elifarley

src/cedarmapper/cli/main.py

@@ -4,16 +4,15 @@
 
 import sys
 from pathlib import Path
-from typing import Optional, Tuple
 
 import click
 
 from cedarmapper.core.walker import walk_directory
-from cedarmapper.render.tree import render_tree
 from cedarmapper.render.flat import render_flat
+from cedarmapper.render.tree import render_tree
 
 
-def run_cli(argv: Optional[list[str]] = None) -> Tuple[int, str]:
+def run_cli(argv: list[str] | None = None) -> tuple[int, str]:
     """
     Programmatic entrypoint used by tests.
 
@@ -167,7 +166,7 @@ def cli(
 
 
 # Keep a small compatibility alias for direct calls (tests should use run_cli)
-def main(argv: Optional[list[str]] = None) -> int:
+def main(argv: list[str] | None = None) -> int:
     code, _ = run_cli(argv)
     return code
 

src/cedarmapper/core/analyzer.py

@@ -2,12 +2,10 @@
 
 from __future__ import annotations
 
-import os
 import subprocess
 from datetime import datetime
 from pathlib import Path
 from shutil import which
-from typing import Optional
 
 from .model import FileInfo
 
@@ -16,7 +14,7 @@ def _tool_exists(name: str) -> bool:
     return which(name) is not None
 
 
-def is_binary_by_file_tool(path: Path) -> Optional[bool]:
+def is_binary_by_file_tool(path: Path) -> bool | None:
     """Return True if binary, False if text; None if tool missing or error."""
     if not _tool_exists("file"):
         return None
@@ -37,7 +35,7 @@ def is_binary_by_file_tool(path: Path) -> Optional[bool]:
         return None
 
 
-def count_words_with_wc(path: Path) -> Optional[int]:
+def count_words_with_wc(path: Path) -> int | None:
     """Return word count (int) or None if wc missing or error."""
     if not _tool_exists("wc"):
         return None

src/cedarmapper/core/model.py

@@ -5,16 +5,15 @@
 from dataclasses import dataclass, field
 from datetime import datetime
 from pathlib import Path
-from typing import List, Optional, Union
 
 
 @dataclass
 class FileInfo:
     path: Path
     size_bytes: int
-    word_count: Optional[int]  # None for binary or skipped
+    word_count: int | None  # None for binary or skipped
     mtime: datetime
-    error: Optional[str] = None  # store error strings (permissions/tool missing)
+    error: str | None = None  # store error strings (permissions/tool missing)
 
 
 @dataclass
@@ -23,5 +22,5 @@ class DirInfo:
     size_bytes: int
     word_count: int  # sum of non-binary file word_counts (binary files contribute 0)
     mtime: datetime  # most recent modification time among contained files
-    children: List[Union["DirInfo", FileInfo]] = field(default_factory=list)
-    error: Optional[str] = None
+    children: list[DirInfo | FileInfo] = field(default_factory=list)
+    error: str | None = None

src/cedarmapper/core/walker.py

@@ -4,7 +4,6 @@
 
 from datetime import datetime
 from pathlib import Path
-from typing import Set, Union
 
 from .analyzer import get_file_info
 from .model import DirInfo, FileInfo
@@ -15,13 +14,13 @@ def walk_directory(
 ) -> DirInfo:
     """Traverse directory tree, always fully descend for aggregation."""
     root = root.resolve()
-    seen_inodes: Set[tuple[int, int]] = set()  # (st_dev, st_ino)
+    seen_inodes: set[tuple[int, int]] = set()  # (st_dev, st_ino)
 
     def _walk(p: Path) -> DirInfo:
         total_bytes = 0
         total_words = 0
         most_recent = datetime.fromtimestamp(0)
-        children = []
+        children: list[DirInfo | FileInfo] = []
 
         try:
             for entry in sorted(p.iterdir(), key=lambda x: x.name):

src/cedarmapper/render/flat.py

@@ -3,11 +3,10 @@
 from __future__ import annotations
 
 from datetime import datetime
-from typing import List, Union
+from functools import cmp_to_key
 
 from cedarmapper.core.model import DirInfo, FileInfo
-from cedarmapper.render.sort import parse_sort_spec, make_comparator
-from functools import cmp_to_key
+from cedarmapper.render.sort import make_comparator, parse_sort_spec
 
 
 def _fmt_count(c: int | None) -> str:
@@ -59,9 +58,9 @@ def render_flat(
     - date_mode: 'seconds' | 'day' | 'none'
     - sort_spec: string describing sorting like 'wi-sd'
     """
-    rows: List[_DisplayRow] = []
+    rows: list[_DisplayRow] = []
 
-    def _render_node(node: Union[DirInfo, FileInfo], depth: int, parent_path: str) -> None:
+    def _render_node(node: DirInfo | FileInfo, depth: int, parent_path: str) -> None:
         display_path = (
             f"{parent_path}{node.path.name}"
             if isinstance(node, FileInfo)
@@ -108,7 +107,7 @@ def _render_node(node: Union[DirInfo, FileInfo], depth: int, parent_path: str) -
         rows.sort(key=cmp_to_key(comp))
 
     # Build lines
-    lines: List[str] = []
+    lines: list[str] = []
     for r in rows:
         date_str = _fmt_mtime(r.mtime, date_mode)
         if date_mode == "none":

src/cedarmapper/render/sort.py

@@ -18,9 +18,8 @@
 
 from __future__ import annotations
 
+from collections.abc import Callable, Iterable
 from dataclasses import dataclass
-from functools import cmp_to_key
-from typing import Callable, Iterable, List, Tuple, Union
 from datetime import datetime
 
 
@@ -31,9 +30,9 @@ class SortSpec:
     reverse: bool = False
 
 
-def parse_sort_spec(spec: str) -> List[SortSpec]:
+def parse_sort_spec(spec: str) -> list[SortSpec]:
     """Parse a spec string like 'wi-sd' into [SortSpec(...), ...]."""
-    specs: List[SortSpec] = []
+    specs: list[SortSpec] = []
     if not spec:
         return specs
     negate = False
@@ -48,7 +47,7 @@ def parse_sort_spec(spec: str) -> List[SortSpec]:
     return specs
 
 
-def _safe_num(v: Union[int, None]) -> float:
+def _safe_num(v: int | None) -> float:
     """Normalize numeric values; treat None as -inf so that present numbers sort after absent ones."""
     if v is None:
         return float("-inf")
@@ -76,6 +75,9 @@ def _cmp(a, b) -> int:
             key = s.key
             rev = -1 if s.reverse else 1
 
+            va: float | str
+            vb: float | str
+
             if key == "w":
                 va = _safe_num(a.word_count)
                 vb = _safe_num(b.word_count)
@@ -105,9 +107,9 @@ def _cmp(a, b) -> int:
                     return 1 * rev
             else:
                 # string comparison
-                if va < vb:
+                if va < vb:  # type: ignore[operator]
                     return -1 * rev
-                if va > vb:
+                if va > vb:  # type: ignore[operator]
                     return 1 * rev
             # else equal -> continue to next spec
         return 0

src/cedarmapper/render/tree.py

@@ -3,11 +3,10 @@
 from __future__ import annotations
 
 from datetime import datetime
-from typing import List, Union
+from functools import cmp_to_key
 
 from cedarmapper.core.model import DirInfo, FileInfo
-from cedarmapper.render.sort import parse_sort_spec, make_comparator
-from functools import cmp_to_key
+from cedarmapper.render.sort import make_comparator, parse_sort_spec
 
 
 def _fmt_count(c: int | None) -> str:
@@ -43,7 +42,7 @@ def render_tree(
     - numbered_indent: if True, prefix each entry with the node depth number instead of indent chars.
     - sort_spec: sort string passed to parse_sort_spec
     """
-    lines: List[str] = []
+    lines: list[str] = []
 
     # Characters used for branches (similar to `tree` command)
     VERTICAL = "│"
@@ -58,18 +57,18 @@ def render_tree(
         comparator = make_comparator(specs)
 
     def _render_node(
-        node: Union[DirInfo, FileInfo],
+        node: DirInfo | FileInfo,
         depth: int,
-        is_last_stack: List[bool],  # stack indicating whether current ancestor is last
+        is_last_stack: list[bool],  # stack indicating whether current ancestor is last
         parent_display_path: str,
     ) -> None:
         # Build prefix either with numbered indent or with branch characters
         if numbered_indent:
             prefix = f"{depth:>3} "
         else:
             # build tree-like prefix
-            prefix_parts: List[str] = []
-            for i, is_last in enumerate(is_last_stack[:-1]):
+            prefix_parts: list[str] = []
+            for _i, is_last in enumerate(is_last_stack[:-1]):
                 prefix_parts.append("   " if is_last else f"{VERTICAL}  ")
             if len(is_last_stack) > 0:
                 prefix_parts.append(LAST if is_last_stack[-1] else BRANCH)

tests/test_analyzer.py

@@ -3,9 +3,7 @@
 import tempfile
 from pathlib import Path
 
-import pytest
-
-from cedarmapper.core.analyzer import _heuristic_is_binary, get_file_info, is_binary_by_file_tool
+from cedarmapper.core.analyzer import _heuristic_is_binary, get_file_info
 
 
 class TestHeuristicBinary:

tests/test_cli.py

@@ -3,8 +3,6 @@
 import tempfile
 from pathlib import Path
 
-import pytest
-
 from cedarmapper.cli.main import run_cli
 
 

tests/test_sort.py

@@ -1,4 +1,4 @@
-from cedarmapper.render.sort import parse_sort_spec, SortSpec
+from cedarmapper.render.sort import SortSpec, parse_sort_spec
 
 
 def test_parse_simple_keys():