10 Common Pine Script Mistakes to Avoid

Learn from common errors that beginner and intermediate Pine Script developers make. Avoid these pitfalls to write better, more reliable code.

1. Repainting Indicators

The Problem: Indicator values change after the bar closes, showing misleading historical signals.

Common Cause: Using security() without proper settings.

❌ Wrong: htfClose = request.security(syminfo.tickerid, "D", close)
✅ Correct: htfClose = request.security(syminfo.tickerid, "D", close, barmerge.gaps_off, barmerge.lookahead_off)

2. Not Understanding Variable Scope

The Problem: Variables behave unexpectedly due to scope issues.

// Global scope
var float myVar = 0

// Updates every bar
if close > open
myVar := myVar + 1

3. Forgetting to Handle NA Values

Indicators often return na on early bars. Always check:

sma20 = ta.sma(close, 20)

// Safe comparison
buySignal = not na(sma20) and close > sma20

4. Inefficient Loop Usage

The Problem: Using loops when built-in functions are available.

❌ Slow: 
sum = 0.0
for i = 0 to 19
    sum := sum + close[i]
average = sum / 20
✅ Fast: average = ta.sma(close, 20)

5. Ignoring Max Bar Reference Limit

Pine Script limits how far back you can reference. Use max_bars_back if needed:

//@version=5
indicator("My Indicator", max_bars_back=5000)

6. Incorrect Strategy Entry/Exit Logic

Common Error: Using indicators on the same bar for entry and exit.

❌ Wrong: May exit and re-enter on same bar

Solution: Use strategy.position_size to check if in position first.

7. Not Testing on Different Timeframes

Code that works on 1H may break on 1D. Always test across multiple timeframes.

8. Hardcoding Values Instead of Inputs

❌ Bad: length = 14 // Hardcoded
✅ Good: length = input.int(14, "Length", minval=1) // User can adjust

9. Poor Code Organization

Use comments and organize code into logical sections:

  • Inputs at top
  • Calculations in middle
  • Plots/alerts at bottom
  • Clear comments explaining logic

10. Not Reading Error Messages Carefully

Pine Script error messages are usually clear. Read them carefully:

  • "Cannot call ... with argument ..." - Type mismatch
  • "Undeclared identifier" - Variable not defined
  • "Script could not be translated" - Syntax error

Debugging Tips

  1. Use plot() to visualize intermediate values
  2. Add labels with label.new() for debugging
  3. Test on different symbols and timeframes
  4. Start simple, add complexity gradually
  5. Use Pine Script community for help

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