systematic-debugging

# Systematic Debugging - Multi-Language > **IMPORTANT:** This skill auto-detects the project language and applies appropriate debugging tools. > **Source:** Based on superpowers/debugging methodology --- ## 🔍 Auto-Detección de Lenguaje ``` Detecta automáticamente el lenguaje: ├── .py → Python debugging ├── .java → Java debugging ├── .cs → C# debugging ├── .go → Go debugging ├── .rs → Rust debugging ├── .rb → Ruby debugging ├── .ts/.js → JS/TS debugging ├── .php → PHP debugging ├── .swift → Swift debugging └── .kt → Kotlin debugging ``` --- ## 🔧 Herramientas de Debugging por Lenguaje ### Python | Herramienta | Propósito | Comando | |-------------|-----------|---------| | **pdb** | Debugger interactivo | `python -m pdb script.py` | | **breakpoint()** | Debugger moderno (Python 3.7+) | `breakpoint()` | | **pytest --capture** | Debug de tests | `pytest -s` | | **ipdb** | Mejor debugger | `pip install ipdb; python -m ipdb script.py` | | **snoop** | Decorator para debug | `pip install snoop` | | **Pyright** | Type checking | `pyright script.py` | ```python # Python: Ejemplo de debugging import pdb def get_user(user_id): breakpoint() # Entra en modo debug user = db.query(user_id) pdb.set_trace() # Alternativa return user ``` ### JavaScript / TypeScript | Herramienta | Propósito | Comando | |-------------|-----------|---------| | **Chrome DevTools** | Debug en navegador | F12 → Console/Sources | | **Node debugger** | Debug en Node | `node --inspect script.js` | | **VS Code** | Debugger integrado | F5 | | **console.log** | Logging básico | `console.log()` | | **ndb** | Better Node debug | `npx ndb script.js` | ```javascript // JavaScript: Debugging console.log('Debug:', variable); // Basic debugger; // Breakpoint en DevTools ``` ### Go | Herramienta | Propósito | Comando | |-------------|-----------|---------| | **Delve** | Debugger oficial | `dlv debug ./package` | | **go test -v** | Verbose testing | `go test -v` | | **log** | Logging | `import "log"` | | **fmt.Printf** | Print debugging | `fmt.Printf("%+v", value)` | ```go // Go: Debugging import ( "fmt" "log" ) func main() { // Printf con formato fmt.Printf("User: %+v\n", user) // Logging log.Printf("Processing user: %d", userID) } ``` ### Rust | Herramienta | Propósito | Comando | |-------------|-----------|---------| | **rust-gdb/rust-lldb** | Debugger | `cargo debug` → GDB/LLDB | | **rust-analyzer** | IDE integration | VS Code + rust-analyzer | | **RUST_BACKTRACE** | Stack traces | `RUST_BACKTRACE=1 cargo run` | | **println! debug** | Print debugging | `println!("{:?}", value)` | ```rust // Rust: Debugging println!("Debug: {:?}", value); // Debug trait eprintln!("Error: {}", error); // Error output // Con Backtrace RUST_BACKTRACE=1 cargo run ``` ### Java | Herramienta | Propósito | Comando | |-------------|-----------|---------| | **jdb** | Debugger命令行 | `jdb -classpath . MyClass` | | **jConsole** | JMX monitoring | `jconsole` | | **VisualVM** | Profiling | `jvisualvm` | | **IntelliJ/Eclipse** | IDE debug | F5/F6 | ### C# / .NET | Herramienta | Propósito | Comando | |-------------|-----------|---------| | **dotnet-sos** | Debugging tools | `dotnet tool install -g dotnet-sos` | | **VS** | Visual Studio debugger | F5 | | **VS Code** | C# debugger | F5 | | **Rider** | JetBrains debugger | F7 | ### Ruby | Herramienta | Propósito | Comando | |-------------|-----------|---------| | **byebug** | Debugger | `require 'byebug'; byebug` | | **pry** | REPL debugger | `binding.pry` | | **IRB** | Interactive Ruby | `irb` | ```ruby # Ruby: Debugging require 'byebug' byebug # or binding.pry ``` ### PHP | Herramienta | Propósito | Comando | |-------------|-----------|---------| | **Xdebug** | Debugger | `xdebug` extension | | **phpdbg** | Debugger CLI | `phpdbg` | | **var_dump** | Dump variables | `var_dump($var)` | --- ## 📋 4-Phase Debugging Process ### Phase 1: Reproduce **Before fixing, reliably reproduce the issue.** ```markdown ## Reproduction Steps 1. [Exact step to reproduce] 2. [Next step] 3. [Expected vs actual result] ## Reproduction Rate - [ ] Always (100%) - [ ] Often (50-90%) - [ ] Sometimes (10-50%) - [ ] Rare (<10%) ``` **Language-specific commands:** ```bash # Python: Reproduce with error python script.py 2>&1 # Go: Reproduce with stack trace RACE_DETECTION_ENABLED=1 go run -race main.go # Rust: Reproduce with backtrace RUST_BACKTRACE=full cargo run ``` ### Phase 2: Isolate **Narrow down the source.** ```markdown ## Isolation Questions - When did this start happening? - What changed recently? - Does it happen in all environments? - Can we reproduce with minimal code? - What's the smallest change that triggers it? ``` **Techniques by language:** ```python # Python: Reduce to minimal case def test_minimal(): # Isolate the failing path pass ``` ```go // Go: Isolate with isolated unit test func Test_isolated(t *testing.T) { // Test only the failing function } ``` ### Phase 3: Understand **Find the root cause, not just symptoms.** ```markdown ## Root Cause Analysis ### The 5 Whys 1. Why: [First observation] 2. Why: [Deeper reason] 3. Why: [Still deeper] 4. Why: [Getting closer] 5. Why: [Root cause] ``` ### Phase 4: Fix & Verify **Fix and verify it's truly fixed.** ```markdown ## Fix Verification - [ ] Bug no longer reproduces - [ ] Related functionality still works - [ ] No new issues introduced - [ ] Test added to prevent regression ``` --- ## 🛠️ Debugging Checklist ```markdown ## Before Starting - [ ] Can reproduce consistently? - [ ] Have minimal reproduction case? - [ ] Understand expected behavior? - [ ] Know what language/runtime? ## During Investigation (Language-adapted) - [ ] Check recent changes (git log) - [ ] Check logs for errors - [ ] Add logging/debug statements - [ ] Use language-appropriate debugger ## After Fix - [ ] Root cause documented? - [ ] Fix verified? - [ ] Regression test added? - [ ] Similar code checked? ``` --- ## 🔧 Common Debugging Commands (Multi-Language) ### Recent Changes ```bash # All languages git log --oneline -20 git diff HEAD~5 ``` ### Search for Errors ```bash # Python grep -r "Error" --include="*.py" . # TypeScript grep -r "throw new Error" --include="*.ts" . # Go grep -r "error" --include="*.go" . ``` ### Check Logs ```bash # System pm2 logs app-name --err --lines 100 # Node.js journalctl -u service -n 50 # Linux systemd docker logs container-name --tail 50 # Docker ``` --- ## 🚫 Anti-Patterns (Language-Agnostic) ❌ **Random changes** - "Maybe if I change this..." ❌ **Ignoring evidence** - "That can't be the cause" ❌ **Assuming** - "It must be X" without proof ❌ **Not reproducing first** - Fixing blindly ❌ **Stopping at symptoms** - Not finding root cause --- ## 📋 Error Patterns by Language | Language | Common Errors | |----------|---------------| | **Python** | TypeError, NameError, ImportError | | **JavaScript** | TypeError, undefined is not a function | | **Go** | nil pointer dereference, race conditions | | **Rust** | borrow checker errors, Option/Result | | **Java** | NullPointerException, ClassNotFoundException | | **C#** | NullReferenceException, StackOverflowException | | **Ruby** | NoMethodError, TypeError | | **PHP** | Undefined index, Call to undefined function | --- ## 🧪 Quick Debug Commands by Language ```bash # Python - Verbose error trace python -v script.py # Node.js - Debug mode NODE_DEBUG=模块 node script.js # Go - Race detector go run -race main.go # Rust - Full backtrace RUST_BACKTRACE=full cargo test # Ruby - Debug mode ruby -d script.rb # PHP - Xdebug php -d xdebug.mode=debug script.php ``` > **Remember:** The debugging methodology is the same for all languages. > Only the **tools and commands** differ. Adapt accordingly.