fix: handle mixed quotes in find_paren_match (#569)

Track the single active quote character instead of separate single and
double quote flags. An apostrophe inside a double quoted string 
(or vice versa) previously left a flag set, hiding the closing parenthesis.

Author: syahra712

CHANGELOG.md

@@ -9,6 +9,8 @@
 - Fixed crash at initialization when a glob in `source_dirs` or `include_dirs`
   matched a dangling symlink
   ([#536](https://github.com/fortran-lang/fortls/issues/536))
+- Fixed declarations and `ASSOCIATE` blocks being dropped when a string inside
+  parentheses contained the other quote character, e.g. `len("don't")`
 
 ## 3.2.2
 

fortls/helper_functions.py

@@ -266,13 +266,24 @@ def find_paren_match(string: str) -> int:
 
     >>> find_paren_match("nt(sin(0.5))+8+len('ab))c')-3) :: y")
     29
+
+    A quote of the other kind inside a string literal does not end the literal
+
+    >>> find_paren_match('''len("don't")) :: msg''')
+    12
+
+    >>> find_paren_match('''len('say "hi')) :: msg''')
+    14
     """
     paren_count = 1
-    quote_state = {"'": False, '"': False}
+    quote = None
     for i, char in enumerate(string):
-        if char in quote_state:
-            quote_state[char] = not quote_state[char]
-        if any(quote_state.values()):
+        if quote is not None:
+            if char == quote:
+                quote = None
+            continue
+        if char in ("'", '"'):
+            quote = char
             continue
 
         if char == "(":

test/test_parser.py

@@ -96,3 +96,26 @@ def calc_result(res: tuple):
     res = file.get_code_line(line_no=ln_no, pp_content=pp)
     result = calc_result(res)
     assert result == reference
+
+
+def test_mixed_quotes_in_parenthesised_strings():
+    file = FortranFile()
+    file.set_contents(
+        [
+            "program test",
+            "  implicit none",
+            """  character(len=len("don't")) :: msg""",
+            "  integer :: x",
+            """  associate (a => "it's", b => x)""",
+            "  end associate",
+            "end program test",
+        ]
+    )
+    ast = file.parse()
+    program, assoc = ast.scope_list
+    assert [child.name for child in program.get_children()] == [
+        "msg",
+        "x",
+        "#ASSOC1",
+    ]
+    assert [child.name for child in assoc.get_children()] == ["a", "b"]