pentaho/pentaho-kettle · error · RuntimeException

Please provide a valid Char to the fillString

Error message

Please provide a valid Char to the fillString

What it means

fillString repeats a single character count times to produce a padded string. The first argument must be a string of exactly length 1; if fillChar.length() != 1 the function throws this RuntimeException. It is a value validation on the character argument, distinct from the argument-count check.

Solutions

1. Pass exactly one character: fillString('-', 10) or fillString(' ', 10).
2. If you need a multi-character pad, use JavaScript repetition instead: new Array(n+1).join(pad).
3. Trim or validate the field feeding the argument before the call.

Example fix

// before
var pad = fillString('--', 20);
// after
var pad = fillString('-', 20);

if (typeof fillChar !== 'string' || fillChar.length !== 1) {
  throw new Error('fillString first argument must be a single character');
}
var padded = fillString(fillChar, count);

function isSingleChar(v) { return typeof v === 'string' && v.length === 1; }

try {
  var padded = fillString(fillChar, count);
} catch (e) {
  if (String(e.message).indexOf('valid Char') !== -1) {
    var padded = fillString(String(fillChar).charAt(0), count);
  } else { throw e; }
}

When it happens

Trigger: Calling fillString('ab', 5) or fillString('', 5) — any first argument whose string length is not exactly 1 while the argument count itself is correct (2 arguments).

Common situations: Passing multi-character pad strings like '--' or ' ' expecting them to be repeated; passing an empty string because the field was empty in the stream.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• The function call initCap requires 1 argument.
• The function call lower is not valid
• The function call ltrim requires 1 argument.
• The function call removeDigits requires 1 argument.
• The function call rtrim requires 1 argument.

AI-assisted analysis of pentaho/pentaho-kettle@f3058517a1 (2026-09-13). Data as JSON: /api/errors/51c213d04112b8bf. Report an issue: GitHub.

Appendix: source

Thrown at engine/src/main/java/org/pentaho/di/trans/steps/script/ScriptAddedFunctions.java:697

      }
    } else {
      throw new RuntimeException( "The function call dateAdd requires 3 arguments." );
    }
  }

  public static String fillString( ScriptEngine actualContext, Bindings actualObject, Object[] ArgList,
    Object FunctionContext ) {
    if ( ArgList.length == 2 ) {
      try {
        if ( isNull( ArgList, new int[] { 0, 1 } ) ) {
          return null;
        } else if ( isUndefined( ArgList, new int[] { 0, 1 } ) ) {
          return (String) undefinedValue;
        }
        String fillChar = (String) ArgList[0];
        int count = (Integer) ArgList[1];
        if ( fillChar.length() != 1 ) {
          throw new RuntimeException( "Please provide a valid Char to the fillString" );
        } else {
          char[] chars = new char[count];
          while ( count > 0 ) {
            chars[--count] = fillChar.charAt( 0 );
          }
          return new String( chars );
        }
      } catch ( Exception e ) {
        throw new RuntimeException( e.toString() );
      }
    } else {
      throw new RuntimeException( "The function call fillString requires 2 arguments." );
    }
  }

  public static Object isCodepage( ScriptEngine actualContext, Bindings actualObject, Object[] ArgList,
    Object FunctionContext ) {
    boolean bRC = false;

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