Add error handling for extract of incomplete block

CHANGELOG.md

@@ -12,6 +12,7 @@
 - #719 Allows the in-memory db to be shared across threads (@tkrabel)
 - #720 create one sqlite3.Connection per thread using a thread local (@tkrabel)
 - #715 change AutoImport's `get_modules` to be case sensitive (@bagel897)
+- #734 raise exception when extracting the start of a block without the end
 
 # Release 1.10.0
 

rope/refactor/extract.py

@@ -444,8 +444,10 @@ def __call__(self, info):
     def base_conditions(self, info):
         if info.region[1] > info.scope_region[1]:
             raise RefactoringError("Bad region selected for extract method")
+
         end_line = info.region_lines[1]
         end_scope = info.global_scope.get_inner_scope_for_line(end_line)
+
         if end_scope != info.scope and end_scope.get_end() != end_line:
             raise RefactoringError("Bad region selected for extract method")
         try:
@@ -498,6 +500,33 @@ def multi_line_conditions(self, info):
                 "Extracted piece should contain complete statements."
             )
 
+        if self._is_region_incomplete_block(info):
+            raise RefactoringError(
+                "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

rope/refactor/sourceutils.py

@@ -1,4 +1,5 @@
 from rope.base import codeanalyze
+from typing import Optional
 
 
 def get_indents(lines, lineno):
@@ -91,3 +92,16 @@ 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

@@ -1149,6 +1149,64 @@ def xxx_test_raising_exception_on_function_parens(self):
         end = code.rindex(")") + 1
         with self.assertRaises(rope.base.exceptions.RefactoringError):
             self.do_extract_method(code, start, end, "new_func")
+
+    def test_raising_exception_on_incomplete_block(self):
+        code = dedent("""\
+            if True:
+                a = 1
+                b = 2
+        """)
+        start = code.index("if")
+        end = code.index("1") + 1
+        with self.assertRaises(rope.base.exceptions.RefactoringError):
+            self.do_extract_method(code, start, end, "new_func")
+
+    def test_raising_exception_on_incomplete_block_2(self):
+        code = dedent("""\
+            if True:
+                a = 1
+            #
+                b = 2
+        """)
+        start = code.index("if")
+        end = code.index("1") + 1
+        with self.assertRaises(rope.base.exceptions.RefactoringError):
+            self.do_extract_method(code, start, end, "new_func")
+
+    def test_raising_exception_on_incomplete_block_3(self):
+        code = dedent("""\
+            if True:
+                a = 1
+            
+                b = 2
+        """)
+        start = code.index("if")
+        end = code.index("1") + 1
+        with self.assertRaises(rope.base.exceptions.RefactoringError):
+            self.do_extract_method(code, start, end, "new_func")
+
+    def test_raising_exception_on_incomplete_block_4(self):
+        code = dedent("""\
+                #
+            if True:
+                a = 1
+                b = 2
+        """)
+        start = code.index("#")
+        end = code.index("1") + 1
+        with self.assertRaises(rope.base.exceptions.RefactoringError):
+            self.do_extract_method(code, start, end, "new_func")
+
+    def test_raising_exception_on_incomplete_block_5(self):
+        code = dedent("""\
+            if True:
+                if 0:
+                    a = 1
+        """)
+        start = code.index("if")
+        end = code.index("0:") + 2
+        with self.assertRaises(rope.base.exceptions.RefactoringError):
+            self.do_extract_method(code, start, end, "new_func")
 
     def test_extract_method_and_extra_blank_lines(self):
         code = dedent("""\