Fix typo in Visitor._validate_func error message for operators

[eye-gu]

Checked other resources

• This is a bug, not a usage question.
• I added a clear and descriptive title that summarizes this issue.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).
• This is not related to the langchain-community package.
• I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS.

Package (Required)

• langchain
• langchain-openai
• langchain-anthropic
• langchain-classic
• langchain-core
• langchain-model-profiles
• langchain-tests
• langchain-text-splitters
• langchain-chroma
• langchain-deepseek
• langchain-exa
• langchain-fireworks
• langchain-groq
• langchain-huggingface
• langchain-mistralai
• langchain-nomic
• langchain-ollama
• langchain-openrouter
• langchain-perplexity
• langchain-qdrant
• langchain-xai
• Other / not sure / general

Related Issues / PRs

No response

Reproduction Steps / Example Code (Python)

from langchain_core.structured_query import Visitor, Operator, Comparator

class TestVisitor(Visitor):
    allowed_comparators = (Comparator.EQ,)
    allowed_operators = (Operator.AND,)

    def visit_operation(self, operation):
        pass

    def visit_comparison(self, comparison):
        pass

    def visit_structured_query(self, structured_query):
        pass

v = TestVisitor()
# Trigger the error with an operator that is not in allowed_operators
v._validate_func(Operator.OR)

Error Message and Stack Trace (if applicable)

ValueError: Received disallowed operator Operator.OR. Allowed comparators are (Operator.AND,)

Description

In Visitor._validate_func (langchain_core/structured_query.py), when an
invalid operator is passed, the error message incorrectly says
"Allowed comparators are ..." instead of "Allowed operators are ...".

This is a copy-paste typo. The message should say "operators" to match
what is actually being validated.

The typo is on line 32:

langchain/libs/core/langchain_core/structured_query.py

Lines 31 to 32 in 8182d63

	f"Received disallowed operator {func}. Allowed "
	f"comparators are {self.allowed_operators}"

System Info

System Information

OS: Darwin
OS Version: Darwin Kernel Version 25.3.0: Wed Jan 28 20:54:55 PST 2026; root:xnu-12377.91.3~2/RELEASE_ARM64_T8132
Python Version: 3.12.11 (main, Jul 23 2025, 00:18:05) [Clang 20.1.4 ]

[pavankalmanoor]

Hey! I spotted this too while going through the codebase, The error message is definitely misleading. I know where the fix needs to go. Would love to take this as my first LangChain contribution if it's up for grabs!

[xyaz1313]

Hey, I'd like to fix this. Simple copy-paste typo - just need to change 'comparators' to 'operators' in the error message. I'll submit a PR right away.

[AKIB473]

Hi, I'd like to work on this issue. The fix is straightforward — the error message in Visitor._validate_func says 'Allowed comparators are' but should say 'Allowed operators are'. I have a fix ready. Could I be assigned?

[slepybear]

Hi! I'd like to work on this issue. The fix is straightforward — changing comparators to operators in the error message at langchain_core/structured_query.py:32 to match the actual variable self.allowed_operators. I have a fix ready and will submit a PR shortly. Could I be assigned?