fix: Recipe slash command doesn't work with single optional parameter

[github-actions]

Closes #6232

Summary

Issue #6232 Fix Summary: Recipe slash command doesn't work with single optional parameter

Problem

Recipe slash commands with optional parameters (having requirement: optional and a default value) incorrectly failed with "Recipe requires 1 parameter(s): filename. Provided: 0" when invoked without providing the optional parameter.

Root Cause

In crates/goose/src/recipe/build_recipe/mod.rs, the function build_recipe_from_template_with_positional_params had an early validation check that compared the number of provided params against the total number of recipe params, without considering whether missing params had default values.

Fix

Modified the validation in build_recipe_from_template_with_positional_params to:

1. Count only required parameters (those without defaults) instead of all parameters
2. Return only the required parameter keys in the error message when params are missing

The fix changes the check from:

if params.len() < recipe_params.len()

to:

let required_count = recipe_params.iter().filter(|p| p.default.is_none()).count();
if params.len() < required_count

Files Changed

1. crates/goose/src/recipe/build_recipe/mod.rs - Modified parameter validation logic
2. crates/goose/src/recipe/build_recipe/tests.rs - Added 4 new tests for positional params with optional parameters

Tests Added

• test_positional_params_single_optional_with_default_no_args - Verifies single optional param works without args
• test_positional_params_single_optional_with_default_with_arg - Verifies optional param can still be overridden
• test_positional_params_required_param_missing_fails - Verifies required params still fail correctly
• test_positional_params_mixed_required_and_optional - Verifies mixed required/optional params work

Verification

• All 52 recipe tests pass
• cargo fmt - clean
• cargo clippy - no errors

---

Generated by goose Issue Solver

[katzdave]

delete this test

[Copilot]

Pull request overview

This PR fixes a bug where recipe slash commands with optional parameters (those having a default value) would incorrectly fail with a "missing parameters" error when invoked without providing the optional parameter. The fix modifies the validation logic in build_recipe_from_template_with_positional_params to distinguish between required and optional parameters.

• Changed parameter validation to only count parameters without defaults as required
• Updated error messages to only list required parameters
• The fix allows optional parameters to be omitted and have their defaults applied via the existing apply_values_to_parameters function