xai-org/x-algorithm · error · SemanticCheckFailure

cannot find class %s

Error message

cannot find class %s

What it means

TypeCompiler.getTypeFromClassName loads a class by name through ClassCache to build a thrift Type. Any loading failure (ClassNotFoundException and friends) is wrapped as SemanticCheckFailure 'cannot find class %s'.

Source

Thrown at botmaker/src/java/com/twitter/botmaker/compiler/types/TypeCompiler.java:99

    }
    ImmutableList.Builder<Type> paramTypesBuilder = ImmutableList.builder();
    for (int i = 1; i < tree.getChildCount(); i++) {
      paramTypesBuilder.add(getType(tree.getChild(i), context));
    }
    return Type.of(info.getFirst(), paramTypesBuilder.build());
  }

  public static Optional<Type> getPrimitiveType(String name) {
    return Type.getPrimitiveTypeFromName(name);
  }

  public static Type getTypeFromClassName(String className) throws SemanticCheckFailure {

    Class<?> clazz;
    try {
      clazz = ClassCache.forName(className);
    } catch (Exception e) {
      throw new SemanticCheckFailure(
          String.format("cannot find class %s", className)
      );
    }

    if (TBase.class.isAssignableFrom(clazz)) {
      return Type.thriftOf((Class<? extends TBase>) clazz);
    } else if (ThriftStruct.class.isAssignableFrom(clazz)) {
      return Type.thriftStructOf((Class<? extends ThriftStruct>) clazz);
    } else {
      throw new SemanticCheckFailure(
          String.format("class has to be either a TBase or ThriftStruct: %s.", className)
      );
    }
  }
}

View on GitHub (pinned to 24c60942c5)

Solutions

1. Verify the fully-qualified name matches the generated class exactly
2. Add the thrift-generated jar containing the class to the botmaker classpath
3. Check shading/relocation rules and classloader parentage
4. Rebuild rules against the current schema's package names

Example fix

// before
Type t = TypeCompiler.getTypeFromClassName("com.acme.oldpkg.User");
// after
Type t = TypeCompiler.getTypeFromClassName("com.acme.newpkg.User");

try { ClassCache.forName(className); } catch (Exception e) {
  throw new IllegalArgumentException("class not on classpath: " + className);
}

catch SemanticCheckFailure 'cannot find class' and surface as deployment/classpath issue with the FQN

When it happens

Trigger: Referring to a fully-qualified thrift struct class in a rule/binding when the class is absent from the classpath — wrong package, typo in FQN, missing jar, or classloader isolation.

Common situations: Deploying rules without the thrift jar containing the struct; renaming the thrift package in the IDL; shading/relocation changing package names; separate classloader environments (app servers) where ClassCache can't see the class.

Related errors

• cannot find class %s
• Cannot load ThriftStruct Codec for %s: $s
• class to be imported has to be either a TBase or ThriftStruc
• Thriftjava objects are not supported in strato JSON
• Failed to create serializer for ThriftStruct %s: %s

AI-assisted analysis of xai-org/x-algorithm@24c60942c5 (2026-08-28). Data as JSON: /api/errors/bd23820e9624eddd. Report an issue: GitHub.