Pine Debugger

Pine Script Debugger

Specialized in adding debugging tools and troubleshooting Pine Script code in TradingView's often opaque environment.

⚠️ Pine Script v6 2025 Common Pitfalls

CRITICAL: March 2025 Breaking Change - For Loop Boundaries

for loops now re-evaluate boundaries every iteration.

PREFERRED FIX: Use `for...in` loops:

// ✅ BEST: Use for...in for arrays (safe and clean)
for element in myArray
    // Process element - safe even if array is modified

// ✅ BEST: Use for...in with index when needed
for [index, element] in myArray
    // Have both index and value

// ✅ for...in works with matrices too
for row in myMatrix
    // row is an array of the current row's values

// ✅ for...in works with maps (key-value pairs)
for [key, value] in myMap
    // Iterate in insertion order

FALLBACK: Cache boundary if traditional `for` is required:

// ❌ BUG: Infinite loop or unexpected behavior
var arr = array.new<int>()
for i = 0 to array.size(arr)  // Re-evaluated each iteration!
    array.push(arr, i)        // Array grows, loop never ends

// ✅ FALLBACK: Cache the boundary before the loop
arrSize = array.size(arr)
for i = 0 to arrSize
    array.push(arr, i)

Debug check: If a loop seems to hang, either switch to for...in or verify boundaries are cached.

Line Continuation Errors

The most common syntax error. Updated rules as of December 2025:

// ❌ ERROR: "end of line without line continuation"
text = condition ?
    "value1" :
    "value2"

// ✅ FIX: Keep ternary on one line
text = condition ? "value1" : "value2"

// ✅ Inside parentheses - any indentation now works (Dec 2025)
plot(series,
    title="Plot",
    color=color.blue)

// ⚠️ Outside parentheses - still requires non-multiple-of-4 indentation
condition = value1 > value2 and
     value3 > value4   // Must use odd indentation (e.g., 5 spaces)

Bid/Ask Variables Return NA

// ❌ UNEXPECTED: Always na on most charts
bidValue = bid  // Only works on 1T (tick) timeframe!

// ✅ DEBUG: Check timeframe
if barstate.islast
    label.new(bar_index, high,
        "Bid: " + (na(bid) ? "N/A (not 1T)" : str.tostring(bid)))

Plot in Local Scope

// ❌ ERROR: "Cannot use 'plot' in local scope"
if condition
    plot(value)

for i = 0 to 10
    plot(close[i])

// ✅ FIX: Use conditional plotting at global scope
plot(condition ? value : na)

Core Debugging Toolkit

1. Label-Based Value Inspector

// Debug label showing multiple values
if barstate.islast
    debugText = "RSI: " + str.tostring(rsiValue, "#.##") + "\n"
    debugText += "MA: " + str.tostring(maValue, "#.##") + "\n"
    debugText += "Signal: " + (buySignal ? "BUY" : "NEUTRAL")
    label.new(bar_index, high * 1.05, debugText,
        style=label.style_label_down,
        color=color.yellow,
        textcolor=color.black)

2. Table-Based Variable Monitor

// Real-time variable monitor table
var table debugTable = table.new(position.top_right, 2, 10,
    bgcolor=color.new(color.black, 80), border_width=1)

if barstate.islast
    table.cell(debugTable, 0, 0, "Variable",
        bgcolor=color.gray, text_color=color.white)
    table.cell(debugTable, 1, 0, "Value",
        bgcolor=color.gray, text_color=color.white)

    table.cell(debugTable, 0, 1, "Bar Index", text_color=color.white)
    table.cell(debugTable, 1, 1, str.tostring(bar_index), text_color=color.yellow)

    table.cell(debugTable, 0, 2, "Close", text_color=color.white)
    table.cell(debugTable, 1, 2, str.tostring(close, "#.####"), text_color=color.yellow)

    table.cell(debugTable, 0, 3, "Signal Active", text_color=color.white)
    sigColor = signalActive ? color.green : color.red
    table.cell(debugTable, 1, 3, signalActive ? "YES" : "NO", text_color=sigColor)

3. Loop Iteration Debugger

// Debug loop iteration (use for...in for safety)
var array<float> values = array.new<float>()
var int loopIterations = 0

loopIterations := 0

// ✅ PREFERRED: Use for...in (safe, no boundary issues)
for [idx, val] in values
    loopIterations += 1
    // Process val directly, idx available if needed

// Alternative: Traditional for with cached boundary
// boundarySize = array.size(values)
// for i = 0 to boundarySize - 1
//     loopIterations += 1

if barstate.islast
    label.new(bar_index, high,
        "Loop ran " + str.tostring(loopIterations) + " times\n" +
        "Array size: " + str.tostring(array.size(values)))

4. Repainting Detector

// Detect potential repainting
var bool repaintDetected = false
var float previousValue = na

if not barstate.isrealtime
    if not na(previousValue) and previousValue != value[1]
        repaintDetected := true
    previousValue := value

if barstate.islast and repaintDetected
    label.new(bar_index, high * 1.1, "⚠️ REPAINTING DETECTED",
        style=label.style_label_down,
        color=color.red,
        textcolor=color.white)

5. NA Value Tracker

// Debug na propagation
debugNa() =>
    result = "NA Debug:\n"
    result += "value1: " + (na(value1) ? "NA ❌" : "OK ✓") + "\n"
    result += "value2: " + (na(value2) ? "NA ❌" : "OK ✓") + "\n"
    result += "result: " + (na(result) ? "NA ❌" : "OK ✓")
    result

if barstate.islast
    label.new(bar_index, low, debugNa(),
        style=label.style_label_up,
        color=color.orange)

6. Security Function Debugger

// Debug request.security() calls
[htfClose, htfTime] = request.security(syminfo.tickerid, "D",
    [close, time],
    lookahead=barmerge.lookahead_off)

if barstate.islast
    secDebug = "HTF Debug:\n"
    secDebug += "Close: " + str.tostring(htfClose, "#.##") + "\n"
    secDebug += "Time: " + str.format_time(htfTime, "yyyy-MM-dd") + "\n"
    secDebug += "Current TF: " + timeframe.period
    label.new(bar_index, high, secDebug)

7. Input Active State Debugger (July 2025)

// Debug conditional inputs
showAdvanced = input.bool(false, "Show Advanced")
advValue = input.int(10, "Advanced Value",
    active=showAdvanced,  // July 2025 feature
    tooltip="This input is conditional")

if barstate.islast
    label.new(bar_index, high,
        "showAdvanced: " + str.tostring(showAdvanced) + "\n" +
        "advValue: " + str.tostring(advValue) + "\n" +
        "(advValue active: " + str.tostring(showAdvanced) + ")")

UDT Debugging Techniques

1. UDT State Inspector

// Debug UDT field values with a method
type Regression
    int startTime
    int endTime
    int startBarIndex
    int endBarIndex
    float slope
    float intercept
    line centerLine = na

// Add debug method to UDT
method debug(Regression this, int yPos) =>
    if barstate.islast and not na(this.startTime)
        debugText = "Regression Debug:\n"
        debugText += "startTime: " + str.format_time(this.startTime, "MM-dd HH:mm") + "\n"
        debugText += "endTime: " + str.format_time(this.endTime, "MM-dd HH:mm") + "\n"
        debugText += "startBar: " + str.tostring(this.startBarIndex) + "\n"
        debugText += "endBar: " + str.tostring(this.endBarIndex) + "\n"
        debugText += "slope: " + str.tostring(this.slope, "#.######") + "\n"
        debugText += "intercept: " + str.tostring(this.intercept, "#.##") + "\n"
        debugText += "hasLine: " + (na(this.centerLine) ? "NO ❌" : "YES ✓")
        label.new(bar_index, yPos, debugText,
            style=label.style_label_left,
            color=color.blue,
            textcolor=color.white)

// Use it
if debugMode
    myRegression.debug(high)

2. UDT Array Inspector Table

// Debug all items in a UDT array
var table udtTable = table.new(position.bottom_left, 6, 12,
    bgcolor=color.new(color.black, 80))

if debugMode and barstate.islast
    // Header row
    table.cell(udtTable, 0, 0, "#", text_color=color.gray)