private Coder inferCoderOrFail()

in sdk/src/main/java/com/google/cloud/dataflow/sdk/values/TypedPValue.java [129:192]
46 lines of code
9 McCabe index (conditional complexity)

  private Coder<T> inferCoderOrFail() {
    // First option for a coder: use the Coder set on this PValue.
    if (coder != null) {
      return coder;
    }

    AppliedPTransform<?, ?, ?> application = getProducingTransformInternal();

    // Second option for a coder: Look in the coder registry.
    CoderRegistry registry = getPipeline().getCoderRegistry();
    TypeDescriptor<T> token = getTypeDescriptor();
    CannotProvideCoderException inferFromTokenException = null;
    if (token != null) {
      try {
          return registry.getDefaultCoder(token);
      } catch (CannotProvideCoderException exc) {
        inferFromTokenException = exc;
        // Attempt to detect when the token came from a TupleTag used for a ParDo side output,
        // and provide a better error message if so. Unfortunately, this information is not
        // directly available from the TypeDescriptor, so infer based on the type of the PTransform
        // and the error message itself.
        if (application.getTransform() instanceof ParDo.BoundMulti
            && exc.getReason() == ReasonCode.TYPE_ERASURE) {
          inferFromTokenException = new CannotProvideCoderException(exc.getMessage()
              + " If this error occurs for a side output of the producing ParDo, verify that the "
              + "TupleTag for this output is constructed with proper type information (see "
              + "TupleTag Javadoc) or explicitly set the Coder to use if this is not possible.");
        }
      }
    }

    // Third option for a coder: use the default Coder from the producing PTransform.
    CannotProvideCoderException inputCoderException;
    try {
      return ((PTransform) application.getTransform()).getDefaultOutputCoder(
          application.getInput(), this);
    } catch (CannotProvideCoderException exc) {
      inputCoderException = exc;
    }

    // Build up the error message and list of causes.
    StringBuilder messageBuilder = new StringBuilder()
        .append("Unable to return a default Coder for ").append(this)
        .append(". Correct one of the following root causes:");

    // No exception, but give the user a message about .setCoder() has not been called.
    messageBuilder.append("\n  No Coder has been manually specified; ")
        .append(" you may do so using .setCoder().");

    if (inferFromTokenException != null) {
      messageBuilder
          .append("\n  Inferring a Coder from the CoderRegistry failed: ")
          .append(inferFromTokenException.getMessage());
    }

    if (inputCoderException != null) {
      messageBuilder
          .append("\n  Using the default output Coder from the producing PTransform failed: ")
          .append(inputCoderException.getMessage());
    }

    // Build and throw the exception.
    throw new IllegalStateException(messageBuilder.toString());
  }