fix(proof): escape backslashes in stub text instead of padding them (#952)

CI caught what my local run did not: appending a space after a trailing
backslash produced '\ ' inside a non-raw docstring — an invalid escape
sequence, which this repo's pytest config escalates from SyntaxWarning to an
error. My fix for an escaping bug introduced a different escaping bug.

Padding a dangerous character is not escaping it. _inline now escapes every
backslash ('\\' renders identically when the docstring is read), which also
covers Windows paths and regexes anywhere in the text, not just at the
delimiter boundary. The trailing-quote case keeps its separating space, which
is safe.

The tests were too weak to catch it: ast.parse succeeds on source that merely
warns. They now assert under warnings.simplefilter('error') and cover
'C:\\path', 're: \\d+' and '\\n' as well as the boundary tails.

Also records the lesson, including: run the CI invocation locally, not a
single-file subset — warning behaviour differs.

Author: frankbria

codeframe/core/proof/stubs.py

@@ -187,17 +187,22 @@ def _inline(text: str) -> str:
     whitespace runs to single spaces and neutralize the sequence that can close
     a docstring from inside one.
 
-    The trailing character matters separately. Six templates butt the text
-    straight against their own closing delimiter — ``\"\"\"Proves: {description}\"\"\"``
-    — so text ending in a single quote yields four in a row: Python closes the
-    docstring on the first three and the fourth opens an unterminated literal.
-    A trailing backslash escapes the delimiter's first quote for the same
-    result. Neither is a ``\"\"\"`` run, so the replacement above does not see
-    them (CI review on #952). One space is enough to separate them, and reads
-    identically.
+    Backslashes are escaped rather than left alone. Inside a non-raw docstring
+    every ``\\x`` is an escape sequence, so a Windows path or a regex in the
+    text emits ``SyntaxWarning: invalid escape sequence`` — an error under this
+    repo's pytest config — and a *trailing* backslash escapes the template's
+    own closing delimiter outright. Doubling renders identically when the
+    docstring is read.
+
+    The trailing quote matters separately. Six templates butt the text straight
+    against their closing delimiter — ``\"\"\"Proves: {description}\"\"\"`` — so text
+    ending in one quote yields four in a row: Python closes the docstring on
+    the first three and the fourth opens an unterminated literal. That is not a
+    ``\"\"\"`` run, so the replacement above does not see it. One space separates
+    them and reads the same.
     """
-    collapsed = " ".join(str(text).split()).replace('"""', "'''")
-    return collapsed + " " if collapsed.endswith(('"', "\\")) else collapsed
+    collapsed = " ".join(str(text).split()).replace("\\", "\\\\").replace('"""', "'''")
+    return collapsed + " " if collapsed.endswith('"') else collapsed
 
 
 def _js_string(text: str) -> str:

tests/core/test_proof9_evidence_integrity_952.py

@@ -502,24 +502,36 @@ class TestTextEndingAtTheDocstringBoundary:
 
     _PY_GATES = [Gate.UNIT, Gate.CONTRACT, Gate.VISUAL, Gate.A11Y, Gate.PERF, Gate.SEC]
 
-    @pytest.mark.parametrize("tail", ['"', '""', "\\", '\\"'])
+    @pytest.mark.parametrize(
+        "tail", ['"', '""', "\\", '\\"', "C:\\path", "re: \\d+", "\\n"]
+    )
     @pytest.mark.parametrize("gate", _PY_GATES)
     def test_a_description_ending_at_the_delimiter_still_parses(self, gate, tail):
+        """Also asserts no SyntaxWarning: a stray backslash makes an invalid
+        escape sequence inside a non-raw docstring, which this repo's pytest
+        config escalates to an error — so a stub that merely *parses* is not
+        enough."""
         import ast
+        import warnings
 
         from codeframe.core.proof.stubs import generate_stubs
 
         req = _requirement("REQ-952-08", "t", f"ends with {tail}", [gate])
-        ast.parse(generate_stubs(req)[gate])
+        with warnings.catch_warnings():
+            warnings.simplefilter("error")
+            ast.parse(generate_stubs(req)[gate])
 
-    @pytest.mark.parametrize("tail", ['"', '""', "\\"])
+    @pytest.mark.parametrize("tail", ['"', '""', "\\", "C:\\path"])
     def test_a_title_ending_at_a_delimiter_still_parses(self, tail):
         import ast
+        import warnings
 
         from codeframe.core.proof.stubs import generate_stubs
 
         req = _requirement("REQ-952-09", f"ends with {tail}", "d", [Gate.UNIT])
-        ast.parse(generate_stubs(req)[Gate.UNIT])
+        with warnings.catch_warnings():
+            warnings.simplefilter("error")
+            ast.parse(generate_stubs(req)[Gate.UNIT])
 
     def test_the_description_is_still_present_and_readable(self):
         from codeframe.core.proof.stubs import generate_stubs