test: add tool_arg_validator edge case test, fix typo (#826) (#831)

* test: add tool_arg_validator edge case test, fix typo (#826)

Add test documenting that tool_arg_validator with tool_name=None
silently returns True when no tool call contains the target arg_name.
Fix "Valiudation" typo in error reason strings.

* fix: error reason interpolates tool_name=None, add issue ref

Use loop variable `tool` instead of `tool_name` in the no-tool-name
branch error message. Add assertion verifying actual tool name appears
in the reason string. Reference #826 in test docstring.

* fix: tidy up tool_arg_validator error messages and guards

- Use `is not None` instead of truthiness check for tool_name
- Fix "Expected None to be called" message when tool_name is None
- Complete truncated docstring for tool_name parameter

* fix: use identity check for tool_label fallback

Consistent with the other is-not-None guards in the function.

Author: planetf1

mellea/stdlib/requirements/tool_reqs.py

@@ -60,11 +60,11 @@ def tool_arg_validator(
 ) -> Requirement:
     """A requirement that passes only if `validation_fn` returns a True value for the *value* of the `arg_name` argument to `tool_name`.
 
-    If `tool_name` is not specified, then this requirement is enforced for *every* tool that
+    If `tool_name` is not specified, then this requirement is enforced for *every* tool that was called.
 
     Args:
         description: The Requirement description.
-        tool_name: The (optional) tool name for .
+        tool_name: The (optional) tool name to validate. When None, all tools are checked.
         arg_name: The argument to check.
         validation_fn: A validation function for validating the value of the `arg_name` argument.
         check_only: propagates the `check_only` flag to the requirement.
@@ -76,20 +76,21 @@ def tool_arg_validator(
     Returns:
         A ``Requirement`` that validates the specified tool argument.
     """
-    if tool_name:
+    if tool_name is not None:
         tool_name = _name2str(tool_name)
 
     def _validate(ctx: Context) -> ValidationResult:
         output = ctx.last_output()
         assert output is not None
 
         if output.tool_calls is None:
+            tool_label = tool_name if tool_name is not None else "a tool"
             return ValidationResult(
                 result=False,
-                reason=f"Expected {tool_name} to be called but no tools were called.",
+                reason=f"Expected {tool_label} to be called but no tools were called.",
             )
 
-        if tool_name:
+        if tool_name is not None:
             if tool_name not in output.tool_calls:
                 return ValidationResult(
                     result=False, reason=f"Tool {tool_name} was not called."
@@ -106,7 +107,7 @@ def _validate(ctx: Context) -> ValidationResult:
             else:
                 return ValidationResult(
                     result=False,
-                    reason=f"Valiudation did not pass for {tool_name}.{arg_name}. Arg value: {arg_value}. Argument validation result: {validate_result}",
+                    reason=f"Validation did not pass for {tool_name}.{arg_name}. Arg value: {arg_value}. Argument validation result: {validate_result}",
                 )
         else:
             for tool in output.tool_calls.keys():
@@ -116,7 +117,7 @@ def _validate(ctx: Context) -> ValidationResult:
                     if not validate_result:
                         return ValidationResult(
                             result=False,
-                            reason=f"Valiudation did not pass for {tool_name}.{arg_name}. Arg value: {arg_value}. Argument validation result: {validate_result}",
+                            reason=f"Validation did not pass for {tool}.{arg_name}. Arg value: {arg_value}. Argument validation result: {validate_result}",
                         )
             return ValidationResult(result=True)
 

test/stdlib/requirements/test_reqlib_tools.py

@@ -185,3 +185,20 @@ def test_tool_arg_validator_no_tool_name_one_fails():
     )
     result = req.validation_fn(ctx)
     assert result.as_bool() is False
+    assert "tool_b" in result.reason
+    assert "None" not in result.reason
+
+
+def test_tool_arg_validator_no_tool_name_arg_missing_everywhere():
+    """Documents current behavior (see #826): when tool_name=None and no tool call
+    contains the target arg_name, validation silently passes (the for-loop completes
+    without failing). This is arguably a latent bug — the validator never runs."""
+    ctx = _ctx_with_tool_calls({"tool_a": _make_tool_call("tool_a", {"y": 5})})
+    req = tool_arg_validator(
+        description="x must be positive",
+        tool_name=None,
+        arg_name="x",
+        validation_fn=lambda v: v > 0,
+    )
+    result = req.validation_fn(ctx)
+    assert result.as_bool() is True