Use AST visitor for extract incomplete block check

Author: raymyers

rope/refactor/extract.py

@@ -499,34 +499,15 @@ def multi_line_conditions(self, info):
             raise RefactoringError(
                 "Extracted piece should contain complete statements."
             )
-
-        if self._is_region_incomplete_block(info):
+        unbalanced_region_finder = _UnbalancedRegionFinder(
+            info.region_lines[0], info.region_lines[1]
+        )
+        unbalanced_region_finder.visit(info.pymodule.ast_node)
+        if unbalanced_region_finder.error:
             raise RefactoringError(
-                "Extracted piece cannot contain the start of a block without the end"
+                "Extracted piece cannot contain the start of a block without the end."
             )
 
-    def _is_region_incomplete_block(self, info):
-        """
-        Is end more indented than start, and does that level continue outside the region?
-        If so, this is an incomplete block that cannot be extracted.
-        """
-
-        def get_effective_indent(lines, line):
-            if found_line := sourceutils.find_nonblank_line(lines, line):
-                return sourceutils.get_indents(info.pymodule.lines, found_line)
-            return None
-
-        start_line = info.region_lines[0]
-        end_line = info.region_lines[1]
-        start_indent = get_effective_indent(info.pymodule.lines, start_line)
-        end_indent = get_effective_indent(info.pymodule.lines, end_line)
-        end_next_indent = get_effective_indent(info.pymodule.lines, end_line + 1)
-        return (
-            end_next_indent is not None
-            and start_indent < end_indent
-            and end_next_indent >= end_indent
-        )
-
     def _is_region_on_a_word(self, info):
         if (
             info.region[0] > 0
@@ -1122,6 +1103,34 @@ def _ClassDef(self, node):
         pass
 
 
+class _UnbalancedRegionFinder(_BaseErrorFinder):
+    """
+    Flag an error if we are including the start of a block without the end.
+    We detect this by ensuring there is no AST node that starts inside the
+    selected range but ends outside of it.
+    """
+
+    def __init__(self, line_start: int, line_end: int):
+        self.error = False
+        self.line_start = line_start
+        self.line_end = line_end
+
+    def generic_visit(self, node: ast.AST):
+        if not hasattr(node, "end_lineno"):
+            super().generic_visit(node)  # Visit children
+            return
+        ends_before_range_starts = node.end_lineno < self.line_start
+        starts_after_range_ends = node.lineno > self.line_end
+        if ends_before_range_starts or starts_after_range_ends:
+            return  # Don't visit children
+        starts_on_or_after_range_start = node.lineno >= self.line_start
+        ends_after_range_ends = node.end_lineno > self.line_end
+        if starts_on_or_after_range_start and ends_after_range_ends:
+            self.error = True
+            return  # Don't visit children
+        super().generic_visit(node)  # Visit children
+
+
 class _GlobalFinder(ast.RopeNodeVisitor):
     def __init__(self):
         self.globals_ = OrderedSet()

rope/refactor/sourceutils.py

@@ -1,5 +1,4 @@
 from rope.base import codeanalyze
-from typing import Optional
 
 
 def get_indents(lines, lineno):
@@ -92,16 +91,3 @@ def get_body_region(defined):
 
 def get_indent(project):
     return project.prefs.get("indent_size", 4)
-
-
-def find_nonblank_line(
-    lines, start_line: int, skip_comments: bool = True
-) -> Optional[int]:
-    """Return index of first non-blank line starting with start_line, None if not found"""
-    next_line = start_line
-    while next_line < lines.length():
-        line_code = lines.get_line(next_line).strip()
-        if line_code and (not skip_comments or not line_code.startswith("#")):
-            return next_line
-        next_line = next_line + 1
-    return None

ropetest/refactor/extracttest.py

@@ -1208,39 +1208,6 @@ def test_raising_exception_on_incomplete_block_5(self):
         with self.assertRaises(rope.base.exceptions.RefactoringError):
             self.do_extract_method(code, start, end, "new_func")
 
-    def test_no_incomplete_error_for_weird_indentation(self):
-        code = dedent("""\
-            def foo():
-                if foo:
-                    s = \"""
-            blah blah
-            blah
-            \"""
-                    print(
-            a, b, c
-                    )
-        """)
-        start = code.index("s =") + 3
-        after_first_triple_quote = code.index('"""') + 3
-        end = code.index('"""', after_first_triple_quote) + 3
-        self.do_extract_method(code, start, end, "new_func")
-
-    def test_no_incomplete_error_for_weird_indentation2(self):
-        code = dedent("""\
-            def foo():
-                print(
-            a, [
-                    3,
-                    4
-                    ],
-                    c
-                    )
-        """)
-        start = code.index("[")
-        end = code.index(']') + 1
-        print(code[start:end])
-        self.do_extract_method(code, start, end, "new_func")
-
     def test_extract_method_and_extra_blank_lines(self):
         code = dedent("""\