Add JSON Schema conditionals for command trigger conflicts with improved error messages

[Copilot]

The compiler enforced command trigger conflicts at runtime (compiler.go:1221), but the schema didn't validate them. This moves validation to parse time using JSON Schema conditionals and adds custom validation with clear, helpful error messages.

Changes

• Schema (main_workflow_schema.json): Added allOf constraint using if/then/not pattern to reject command triggers combined with issues, issue_comment, pull_request, or pull_request_review_comment events

• Custom validation (schema.go): Added validateCommandTriggerConflicts function that runs before schema validation to provide clear, helpful error messages explaining why the conflict exists

• Parser tests (schema_test.go): Added 9 test cases covering invalid conflicts and valid combinations

• Compiler tests (compiler_test.go): Updated error expectations to match new custom validation error messages

Error Messages

Previously, generic schema errors were shown:

error: at '': 'allOf' failed
- at '/on': 'not' failed

Now, clear and helpful messages explain the conflict:

command trigger cannot be used with 'issues' event in the same workflow. 
Command triggers are designed to respond to slash commands in comments 
and should not be combined with event-based triggers for issues or pull requests

For multiple conflicts:

command trigger cannot be used with these events in the same workflow: issues, pull_request. 
Command triggers are designed to respond to slash commands in comments 
and should not be combined with event-based triggers for issues or pull requests

Example

Previously accepted at parse time, caught at compile time:

on:
  command:
    name: test-bot
  issues:
    types: [opened]

Now rejected at parse time with a clear error message.

Valid combinations still work:

on:
  command:
    name: scheduler-bot
  workflow_dispatch:
  schedule:
    - cron: "0 9 * * 1"

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[task] Add JSON Schema conditionals for command trigger conflicts</issue_title>
<issue_description>## Objective
Implement JSON Schema conditionals to enforce that command triggers cannot be used with certain event types (issues, issue_comment, pull_request, pull_request_review_comment).

Context

This addresses Issue #4 from discussion #2969. The compiler enforces this rule at runtime (pkg/workflow/compiler.go:1221), but the schema doesn't validate it. The MCP schemas already use JSON Schema conditionals correctly as a "gold standard" - this task applies that pattern to the main schema.

Approach

1. Study the conditional pattern used in pkg/parser/schemas/mcp_config_schema.json
2. Add if/then/else or not conditionals to main_workflow_schema.json
3. Enforce that when on.command is present, the conflicting events cannot be used
4. Add clear error messages in schema annotations

Files to Modify

• pkg/parser/schemas/main_workflow_schema.json - Add conditionals for command conflicts

Example Pattern

{
  "if": {
    "properties": {
      "on": {"properties": {"command": {"type": "object"}}}
    }
  },
  "then": {
    "not": {
      "properties": {
        "on": {
          "anyOf": [
            {"required": ["issues"]},
            {"required": ["issue_comment"]},
            {"required": ["pull_request"]},
            {"required": ["pull_request_review_comment"]}
          ]
        }
      }
    }
  }
}

Reference Files

• pkg/workflow/compiler.go:1221 - Runtime enforcement logic
• pkg/parser/schemas/mcp_config_schema.json - Gold standard conditional examples

Acceptance Criteria

• Schema rejects workflows with command + conflicting events
• Schema accepts valid command configurations
• Error message is clear and helpful
• Pattern follows MCP schema best practices
• Run make build and make test successfully
  Related to [Schema Consistency] 🔍 Schema Consistency Check - Required Fields & Error Documentation Gap (Nov 2, 2025) #2969

AI generated by Plan Command for discussion #2969</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [task] Add JSON Schema conditionals for command trigger conflicts #2975

---

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[pelikhan]

@copilot improve the error message

[Copilot]

@copilot improve the error message

Improved error message in commit 1df047e.

Before:

error: at '': 'allOf' failed
- at '/on': 'not' failed

After:

command trigger cannot be used with 'issues' event in the same workflow. 
Command triggers are designed to respond to slash commands in comments 
and should not be combined with event-based triggers for issues or pull requests

The error message now:

• Clearly identifies which event conflicts with the command trigger
• Explains why the conflict exists (command triggers are for slash commands)
• Uses natural language instead of generic schema validation errors

[Copilot]

Pull Request Overview

This PR improves error messaging for command trigger validation by adding custom validation and updating error messages to be more descriptive. The changes ensure that when a command trigger is used with conflicting events (issues, issue_comment, pull_request, pull_request_review_comment), users receive clear, helpful error messages explaining why the combination is invalid.

Key changes:

• Added custom validation function validateCommandTriggerConflicts that runs before JSON schema validation to provide clearer error messages
• Updated test expectations to match the new, more descriptive error messages
• Added comprehensive test coverage for command trigger conflict scenarios

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
pkg/parser/schema.go	Added validateCommandTriggerConflicts function and integrated it into the validation pipeline to provide better error messages for command trigger conflicts
pkg/parser/schema_test.go	Added test cases covering various command trigger conflict scenarios and valid command trigger usage patterns
pkg/parser/schemas/main_workflow_schema.json	Added JSON schema validation rules using allOf/if-then to enforce command trigger conflict constraints at the schema level
pkg/workflow/compiler_test.go	Updated expected error messages in existing tests to match the new, more descriptive error format

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