Allow comment in dictionary

README.rst

@@ -293,6 +293,34 @@ applied directly, but should instead be manually inspected. E.g.:
 
        clas->class, clash, disabled because of name clash in c++
 
+Comments in dictionaries
+----------------------------
+
+Dictionary files may contain comments.
+
+1. Pure comment::
+
+       # comment
+        #comment
+
+2. Inline comment must be preceded by whitespace::
+
+       abondon->abandon #comment
+       abondon->abandon # comment
+
+   The ``#`` character is treated as the start of the comment only if it is
+   preceded by whitespace.
+
+3. Invalid comment examples::
+
+       abondon->abandon#comment
+       thenumberone->the#one
+       the#one->thenumberone
+
+   In such cases, the whole line is considered malformed and will be ignored.
+
+4. Blank lines are also ignored.
+
 Development setup
 -----------------
 

codespell_lib/_spellchecker.py

@@ -54,7 +54,17 @@ def build_dict(
     with open(filename, encoding="utf-8") as f:
         translate_tables = [(x, str.maketrans(x, y)) for x, y in alt_chars]
         for line in f:
-            [key, data] = line.split("->")
+            left, pound, _ = line.partition("#")
+            if pound and left and left[-1] not in (" ", "\t"):
+                continue
+
+            line = left.strip()
+            if not line:
+                continue
+            try:
+                key, data = line.split("->")
+            except ValueError:
+                continue
             # TODO: For now, convert both to lower.
             #       Someday we can maybe add support for fixing caps.
             key = key.lower()

codespell_lib/tests/test_basic.py

@@ -1524,3 +1524,36 @@ def test_args_from_file(
     print("Testing with direct call to cs_.main()")
     r = cs_.main(*args[1:])
     print(f"{r=}")
+
+
+def test_dict_comments(
+    tmp_path: Path,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    """Test dictionary comments and blank lines."""
+    fname = tmp_path / "bad.txt"
+    fname.write_text("abandonned\noccured\n")
+
+    dictionary = tmp_path / "test.txt"
+    dictionary.write_text(
+        "#comment\n"
+        "# comment\n"
+        " #comment\n"
+        "\n"
+        "\r\n"
+        "abandonned->abandoned # inline comment\n"
+        "occured->occurred# invalid inline comment\n"
+        "abil#ity->ability # hash in illegal position\n"
+        "ability->#ability # hash in illegal position\n"
+        "abilityability # no arrow\n",
+        encoding="utf-8",
+    )
+
+    # Allow valid inline comments.
+    # Skip entries where '#' is not preceded by whitespace.
+    result = cs.main("-D", dictionary, fname, std=True)
+    assert isinstance(result, tuple)
+    code, stdout, _ = result
+    assert code == 1
+    assert "abandonned ==> abandoned" in stdout
+    assert "occured ==> occurred" not in stdout