apple/pkl · error

adhocEvalError

Error message

adhocEvalError

What it means

Thrown by String.fromBase64() (decoded as UTF-8 text) when the input is not valid Base64. Java's Base64 decoder rejects illegal characters, incorrect padding, or lengths that are not a multiple of 4; the decoder's message is surfaced with the offending string attached.

Solutions

1. Verify the string is valid Base64 (length multiple of 4, correct padding, alphabet A–Z a–z 0–9 + /)
2. Strip any data-URI prefix and whitespace before decoding
3. Convert URL-safe characters: replace '-' with '+' and '_' with '/' for JWT-style payloads
4. Re-encode the source data if the payload is truncated or corrupt

Example fix

// before
val text = jwtPayload.fromBase64()
// after
val text = jwtPayload.replace("-", "+").replace("_", "/").fromBase64()

function isStandardBase64(s: String): Boolean = s.replaceAll("\n", "").isRegexMatch(/^[A-Za-z0-9+/]*={0,2}$/, _) && s.replaceAll("\n", "").length % 4 == 0

When it happens

Trigger: Calling `"not~base64!".fromBase64()`, a Base64 string with wrong padding (e.g. "YWJ"), URL-safe base64 (- and _) fed to the standard decoder, or an empty/malformed payload from an API.

Common situations: Copying tokens or credentials that got truncated or whitespace-mangled; receiving base64url (JWT segments) instead of standard base64; data-URI prefixes ("data:...;base64,") left in the string.

Related errors

• e.getMessage()
• Cannot convert pkl.base#String
• Cannot decode Function value
• cannotParseStringAs
• charIndexOutOfRange

AI-assisted analysis of apple/pkl@f3efcbfc9b (2026-09-08). Data as JSON: /api/errors/18bc340614558382. Report an issue: GitHub.

Appendix: source

Thrown at pkl-core/src/main/java/org/pkl/core/stdlib/base/StringNodes.java:1006

    }
  }

  public abstract static class base64 extends ExternalPropertyNode {
    @TruffleBoundary
    @Specialization
    protected String eval(String self) {
      return ByteArrayUtils.base64(self.getBytes(StandardCharsets.UTF_8));
    }
  }

  public abstract static class base64Decoded extends ExternalPropertyNode {
    @TruffleBoundary
    @Specialization
    protected String eval(String self) {
      try {
        return new String(Base64.getDecoder().decode(self), StandardCharsets.UTF_8);
      } catch (IllegalArgumentException e) {
        throw exceptionBuilder()
            .adhocEvalError(e.getMessage())
            .withProgramValue("String", self)
            .withCause(e)
            .build();
      }
    }
  }

  public abstract static class base64DecodedBytes extends ExternalPropertyNode {
    @TruffleBoundary
    @Specialization
    protected VmBytes eval(String self) {
      try {
        return new VmBytes(Base64.getDecoder().decode(self));
      } catch (IllegalArgumentException e) {
        throw exceptionBuilder()
            .adhocEvalError(e.getMessage())
            .withProgramValue("String", self)

View on GitHub (pinned to f3efcbfc9b)