Pine script compile errors in TradingView

What is causing it

The script uses an old Pine version or has a syntax error.

Why this happens

Pine Script is versioned, and the versions are not compatible with one another. Each release changed function names, argument structures and defaults, so a script written for an older version will not compile under a newer one and the version declaration at the top of the file is what tells the compiler which rules to apply. A script copied from an old forum post or tutorial therefore fails not because it was wrong when written, but because the language has moved on.

The compiler reports the first error it hits, and in a language with strict typing and indentation rules that error is often a symptom of something earlier in the script rather than the actual mistake. A missing argument on one line can produce a complaint about a line further down. Reading upward from the reported line is usually more productive than staring at the line itself.

The fix, step by step

1. Open the Pine Editor and read the error line and message.
2. Check the version tag at the top, such as //@version=5, matches the code.
3. Update deprecated functions if the script was written for an older Pine version.
4. If it is a third-party script, get the latest version from the author.

How to confirm it is fixed

A script that compiles adds to the chart and plots. Watch for a runtime error indicator on the indicator's name after it loads, since a script can compile cleanly and then fail while executing, which is a separate problem from a compile error. Check the values it plots look sensible against the price rather than assuming a clean compile means correct behaviour.

Stopping it happening again

Take scripts from their original published source rather than pasted copies, so you get the maintained version. Note the Pine version a script targets before editing it. If you write your own, make one change at a time and compile after each, which makes it obvious which change broke it.