Bug Reproducer

Isolates a reported issue into a single, reliable reproduction command or script. Proves the existence of a bug before writing fixes.

1. Purpose

Turn ambiguous bug reports into a standalone test case that exits with a failure code (non-zero). A "Reproduction" is a deterministic command that consistently triggers the defect.

2. When to Use

Use this skill when:

• A bug or crash report is received.
• Before modifying source code to fix an issue.
• Isolating whether a bug is in local code or an external dependency.

3. When Not to Use

• Do not use to write or apply the code fix; use minimal-bug-fix.
• Do not use to write permanent test suite integration; use regression-test-writer.
• Do not use to diagnose a build/system command failure; use command-failure-diagnoser.

4. Required Inputs

• bug_report: Description of the faulty behavior, inputs, and expected vs actual results.
• workspace_root: Directory of the target repository.

5. Missing-Input Behavior

1. If expected behavior or actual behavior is omitted: ask the user for the missing expectation.
2. If reproduction steps are vague (e.g. "it failed randomly"): search recent commit logs or issue tickets for stack traces before escalating.
3. Do not modify repository source code while constructing reproductions.

6. Procedure

Follow these numbered actions:

1. Action 1: Identify the Minimal Failing Input
   • Strip away unrelated parameters, large payloads, or background tasks.
2. Action 2: Identify the Entry Point or Trigger Function
   • Find the exact CLI command, HTTP endpoint, or function call.
3. Action 3: Create a Minimal Standalone Reproduction
   • Write a self-contained script or one-line command (e.g. python3 test_repro.py or curl ...).
4. Action 4: Run Reproduction Once
   • Confirm it fails with the reported symptom.
5. Action 5: Emit Reproduction Report
   • Format using Section 8.

7. Decision Rules

• If the command passes instead of failing: the bug is not reproduced. Do not proceed to fix; refine the input parameters.
• If reproduction requires network or paid external APIs: mock or stub the external call locally.
• If reproduction deletes data: use a temporary scratch directory (/tmp or test_scratch/).

8. Output Format

Emit the reproduction report using this template:

### Bug Reproduction: [Bug Title]

- **Status**: [REPRODUCED | UNREPRODUCED | FLAKY]
- **Target File**: `[source file suspected]`
- **Reproduction Command**: `[Exact command]`

#### Minimal Failing Input
```text
[Input payload or invocation]

Observed Output (Failure)

[Exact stderr or traceback]

Expected Output

[What should happen when fixed]

## 9. Verification Checklist
- [ ] The reproduction command was executed and failed with the expected symptom.
- [ ] No production source files were modified.
- [ ] The reproduction does not depend on uncommitted temporary hacks.

## 10. Common Failures and Recovery
| Failure Symptom | Cause | Recovery Action |
| :--- | :--- | :--- |
| Bug does not trigger | Missing environment variables | Inspect `.env.example` and set dummy variables. |
| Non-deterministic failure | Concurrency or timing race | Pin random seeds or reduce concurrency to 1 thread. |

## 11. Stop or Escalation Conditions
Stop and ask the user when:
- The bug requires unavailable hardware, OS-specific features, or external database credentials.

## 12. Examples

### Example 1: Successful Execution
**Input:**
```text
Bug: Calling `formatName("")` throws Uncaught TypeError: Cannot read properties of undefined.
File: src/formatter.js

Output:

### Bug Reproduction: TypeError in formatName on Empty String

- **Status**: REPRODUCED
- **Target File**: `src/formatter.js`
- **Reproduction Command**: `node -e "require('./src/formatter').formatName('')"`

#### Minimal Failing Input
```javascript
formatName("")

Observed Output (Failure)

TypeError: Cannot read properties of undefined (reading 'split')
    at Object.formatName (/src/formatter.js:12:18)

Expected Output

Returns empty string "" without throwing an exception.

### Example 2: Ambiguous or Failure Case
**Input:**
```text
Bug: "Search is broken sometimes."

Output:

### Bug Reproduction: UNREPRODUCED - Insufficient Parameters

- **Status**: UNREPRODUCED
- **Target File**: TBD

The description "Search is broken sometimes" lacks specific search queries, HTTP parameters, or error messages. 
Please provide:
1. An example search query that fails.
2. The user role or authentication state.
3. The observed HTTP status code or UI error.

Example 3: Expected Final Output

Output:

### Bug Reproduction: Zero Division in Discount Calculator

- **Status**: REPRODUCED
- **Target File**: `src/pricing.py`
- **Reproduction Command**: `python3 -c "from src.pricing import calculate_rate; calculate_rate(100, 0)"`

#### Minimal Failing Input
```python
calculate_rate(price=100, original=0)

Observed Output (Failure)

ZeroDivisionError: division by zero

Expected Output

Returns 0.0 or raises InvalidDiscountError.