Warn and continue on syntaxerror

hypothesis-python/RELEASE.rst

@@ -0,0 +1,5 @@
+RELEASE_TYPE: patch
+
+This patch ensures that the :ref:`hypothesis codemod <codemods>` CLI
+will print a warning instead of stopping with an internal error if
+one of your files contains invalid syntax (:issue:`3759`).

hypothesis-python/src/hypothesis/extra/cli.py

@@ -166,7 +166,22 @@ def _refactor(func, fname):
         except (OSError, UnicodeError) as err:
             # Permissions or encoding issue, or file deleted, etc.
             return f"skipping {fname!r} due to {err}"
-        newcode = func(oldcode)
+
+        if "hypothesis" not in oldcode:
+            return  # This is a fast way to avoid running slow no-op codemods
+
+        try:
+            newcode = func(oldcode)
+        except Exception as err:
+            from libcst import ParserSyntaxError
+
+            if isinstance(err, ParserSyntaxError):
+                from hypothesis.extra._patching import indent
+
+                msg = indent(str(err).replace("\n\n", "\n"), "    ").strip()
+                return f"skipping {fname!r} due to {msg}"
+            raise
+
         if newcode != oldcode:
             with open(fname, mode="w", encoding="utf-8") as f:
                 f.write(newcode)