Add DocstringRemover (#197)

* Add DocstringRemover

* fix test

src/latexify/ast_utils.py

@@ -96,6 +96,21 @@ def is_constant(node: ast.AST) -> bool:
         return isinstance(node, ast.Constant)
 
 
+def is_str(node: ast.AST) -> bool:
+    """Checks if the node is a str constant.
+
+    Args:
+        node: The node to examine.
+
+    Returns:
+        True if the node is a str constant, False otherwise.
+    """
+    if sys.version_info.minor < 8 and isinstance(node, ast.Str):
+        return True
+
+    return isinstance(node, ast.Constant) and isinstance(node.value, str)
+
+
 def extract_int_or_none(node: ast.expr) -> int | None:
     """Extracts int constant from the given Constant node.
 

src/latexify/ast_utils_test.py

@@ -114,6 +114,38 @@ def test_is_constant(value: ast.AST, expected: bool) -> None:
     assert ast_utils.is_constant(value) is expected
 
 
+@test_utils.require_at_most(7)
+@pytest.mark.parametrize(
+    "value,expected",
+    [
+        (ast.Bytes(s=b"foo"), False),
+        (ast.Constant("bar"), True),
+        (ast.Ellipsis(), False),
+        (ast.NameConstant(value=None), False),
+        (ast.Num(n=123), False),
+        (ast.Str(s="baz"), True),
+        (ast.Expr(value=ast.Num(456)), False),
+        (ast.Global(names=["qux"]), False),
+    ],
+)
+def test_is_str_legacy(value: ast.AST, expected: bool) -> None:
+    assert ast_utils.is_str(value) is expected
+
+
+@test_utils.require_at_least(8)
+@pytest.mark.parametrize(
+    "value,expected",
+    [
+        (ast.Constant(value=123), False),
+        (ast.Constant(value="foo"), True),
+        (ast.Expr(value=ast.Constant(value="foo")), False),
+        (ast.Global(names=["foo"]), False),
+    ],
+)
+def test_is_str(value: ast.AST, expected: bool) -> None:
+    assert ast_utils.is_str(value) is expected
+
+
 def test_extract_int_or_none() -> None:
     assert ast_utils.extract_int_or_none(ast_utils.make_constant(-123)) == -123
     assert ast_utils.extract_int_or_none(ast_utils.make_constant(0)) == 0

src/latexify/generate_latex.py

@@ -56,6 +56,7 @@ def get_latex(
     if merged_config.identifiers is not None:
         tree = transformers.IdentifierReplacer(merged_config.identifiers).visit(tree)
     if merged_config.reduce_assignments:
+        tree = transformers.DocstringRemover().visit(tree)
         tree = transformers.AssignmentReducer().visit(tree)
     if merged_config.expand_functions is not None:
         tree = transformers.FunctionExpander(merged_config.expand_functions).visit(tree)

src/latexify/generate_latex_test.py

@@ -54,6 +54,20 @@ def f(x):
     assert generate_latex.get_latex(f, reduce_assignments=True) == latex_with_flag
 
 
+def test_get_latex_reduce_assignments_with_docstring() -> None:
+    def f(x):
+        """DocstringRemover is required."""
+        y = 3 * x
+        return y
+
+    latex_without_flag = r"\begin{array}{l} y = 3 x \\ f(x) = y \end{array}"
+    latex_with_flag = r"f(x) = 3 x"
+
+    assert generate_latex.get_latex(f) == latex_without_flag
+    assert generate_latex.get_latex(f, reduce_assignments=False) == latex_without_flag
+    assert generate_latex.get_latex(f, reduce_assignments=True) == latex_with_flag
+
+
 def test_get_latex_reduce_assignments_with_aug_assign() -> None:
     def f(x):
         y = 3

src/latexify/transformers/__init__.py

@@ -2,13 +2,15 @@
 
 from latexify.transformers.assignment_reducer import AssignmentReducer
 from latexify.transformers.aug_assign_replacer import AugAssignReplacer
+from latexify.transformers.docstring_remover import DocstringRemover
 from latexify.transformers.function_expander import FunctionExpander
 from latexify.transformers.identifier_replacer import IdentifierReplacer
 from latexify.transformers.prefix_trimmer import PrefixTrimmer
 
 __all__ = [
     "AssignmentReducer",
     "AugAssignReplacer",
+    "DocstringRemover",
     "FunctionExpander",
     "IdentifierReplacer",
     "PrefixTrimmer",

src/latexify/transformers/docstring_remover.py

@@ -0,0 +1,20 @@
+"""Transformer to remove all docstrings."""
+
+from __future__ import annotations
+
+import ast
+from typing import Union
+
+from latexify import ast_utils
+
+
+class DocstringRemover(ast.NodeTransformer):
+    """NodeTransformer to remove all docstrings.
+
+    Docstrings here are detected as Expr nodes with a single string constant.
+    """
+
+    def visit_Expr(self, node: ast.Expr) -> Union[ast.Expr, None]:
+        if ast_utils.is_str(node.value):
+            return None
+        return node

src/latexify/transformers/docstring_remover_test.py

@@ -0,0 +1,32 @@
+"""Tests for latexify.transformers.docstring_remover."""
+
+import ast
+
+from latexify import ast_utils, parser, test_utils
+from latexify.transformers.docstring_remover import DocstringRemover
+
+
+def test_remove_docstrings() -> None:
+    def f():
+        """Test docstring."""
+        x = 42
+        f()  # This Expr should not be removed.
+        """This string constant should also be removed."""
+        return x
+
+    tree = parser.parse_function(f).body[0]
+    assert isinstance(tree, ast.FunctionDef)
+
+    expected = ast.FunctionDef(
+        name="f",
+        body=[
+            ast.Assign(
+                targets=[ast.Name(id="x", ctx=ast.Store())],
+                value=ast_utils.make_constant(42),
+            ),
+            ast.Expr(value=ast.Call(func=ast.Name(id="f", ctx=ast.Load()))),
+            ast.Return(value=ast.Name(id="x", ctx=ast.Load())),
+        ],
+    )
+    transformed = DocstringRemover().visit(tree)
+    test_utils.assert_ast_equal(transformed, expected)