1 commit

Author	SHA1	Message	Date
Ricardo-M-L	af6504f900	fix(chat_templates): check find() return value before slicing on placeholders (#5763) ... * fix(chat_templates): check find() return value before slicing on placeholders Two places in `construct_chat_template()` use `str.find()` for sentinel placeholders (`{INPUT}` / `{OUTPUT}`) without checking the -1 return: 1. The `except:` fallback (around line 2464) computes `chat_template[chat_template.find("{OUTPUT}") + len("{OUTPUT}"):]`. If the template has no `{OUTPUT}` marker, `find()` returns -1 and the slice starts at offset 7 (`-1 + len("{OUTPUT}")`), producing garbage that's then `re.escape`-d and fed back into the template-recovery regex. The user sees a confusing `IndexError` on `response_part = response_part[0]` instead of the real problem. 2. The final trim before returning (`input_part[:input_part.find("{INPUT}")]` and the matching `{OUTPUT}` line) silently drops the last character when the placeholder is missing — `find()` returns -1, and `[:-1]` slices everything except the last character, returning a corrupted template prefix to the caller. Replace both with an explicit `-1` check that raises a clear `RuntimeError` naming the missing placeholder, matching the existing guard pattern from #4923 (`try_fix_tokenizer`). Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com> * fix(chat_templates): also guard {INPUT} and fallback regex/separator paths Builds on the {OUTPUT} / final-trim guards in this branch by closing the three remaining ways the except-block fallback in construct_chat_template() can still raise a confusing IndexError or AttributeError on malformed templates: 1. Validate both {INPUT} and {OUTPUT} before deriving `ending`. The regex two lines later (`{INPUT} + ending + ...`) still produced an empty list and crashed on `response_part[0]` if {INPUT} was missing. 2. Guard the regex no-match case. Some templates contain both placeholders but not in a recoverable two-example shape, in which case `re.findall` returns an empty list and `[0]` raises. 3. Initialize `found = None` before the separator-search loop and raise if the loop never sets it. Previously, if the first iteration's `re.finditer` was empty the loop broke without binding `found`, and `found.group(1)` raised AttributeError on the stale int left over from the outer rfind loop. Rephrase the final-trim error messages from internal variable names ("input_part") to user-facing wording ("instruction section") and include a bounded (200-char) excerpt of the offending content so the error is debuggable without being unbounded. Add tests/python/test_construct_chat_template_validation.py covering each failure mode with a fake tokenizer (no HF_TOKEN, no model download, CPU-only). * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci --------- Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com> Co-authored-by: Daniel Han <danielhanchen@gmail.com> Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>	2026-05-25 06:19:01 -07:00