Add checks on thrift files based on ID (#846)

Author: vikrantpuppala

src/test/java/com/databricks/jdbc/dbclient/impl/thrift/ThriftGeneratedFieldIdTest.java

@@ -0,0 +1,127 @@
+package com.databricks.jdbc.dbclient.impl.thrift;
+
+import static org.junit.jupiter.api.Assertions.fail;
+
+import com.databricks.jdbc.log.JdbcLogger;
+import com.databricks.jdbc.log.JdbcLoggerFactory;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Stream;
+import org.apache.thrift.TFieldIdEnum;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Validates that all Thrift-generated classes comply with field ID constraints.
+ *
+ * <p>Field IDs in Thrift must stay below 3329 to avoid conflicts with reserved ranges and ensure
+ * compatibility with various Thrift implementations and protocols.
+ */
+public class ThriftGeneratedFieldIdTest {
+  private static final JdbcLogger LOGGER =
+      JdbcLoggerFactory.getLogger(ThriftGeneratedFieldIdTest.class);
+
+  private static final int MAX_ALLOWED_FIELD_ID = 3329;
+  private static final String GENERATED_PACKAGE =
+      "com.databricks.jdbc.model.client.thrift.generated";
+  private static final String GENERATED_DIR =
+      "src/main/java/com/databricks/jdbc/model/client/thrift/generated";
+
+  @Test
+  public void testAllThriftFieldIdsAreWithinAllowedRange() throws IOException {
+    List<String> violations = new ArrayList<>();
+
+    Path generatedDirPath = Paths.get(GENERATED_DIR);
+
+    if (!Files.exists(generatedDirPath)) {
+      fail("Generated directory does not exist: " + GENERATED_DIR);
+    }
+
+    // Find all Java files that might contain Thrift-generated classes
+    try (Stream<Path> javaFiles =
+        Files.walk(generatedDirPath).filter(path -> path.toString().endsWith(".java"))) {
+      javaFiles.forEach(javaFile -> checkFileForFieldIdViolations(javaFile, violations));
+    }
+
+    if (!violations.isEmpty()) {
+      StringBuilder errorMessage = new StringBuilder();
+      errorMessage
+          .append("Found Thrift field IDs that exceed the maximum allowed value of ")
+          .append(MAX_ALLOWED_FIELD_ID)
+          .append(".\nThis can cause compatibility issues and conflicts with reserved ID ranges.\n")
+          .append("Violations found:\n");
+
+      for (String violation : violations) {
+        errorMessage.append("  - ").append(violation).append("\n");
+      }
+
+      fail(errorMessage.toString());
+    }
+  }
+
+  /**
+   * Examines a Java file to determine if it contains a Thrift-generated class and validates that
+   * all field IDs are within the allowed range.
+   */
+  private void checkFileForFieldIdViolations(Path javaFile, List<String> violations) {
+    String fileName = javaFile.getFileName().toString();
+
+    if (!fileName.endsWith(".java")) {
+      return;
+    }
+
+    String className = fileName.substring(0, fileName.length() - 5);
+    String fullClassName = GENERATED_PACKAGE + "." + className;
+
+    try {
+      Class<?> clazz = Class.forName(fullClassName);
+
+      // Look for the _Fields enum that Thrift generates for struct classes
+      // This enum contains metadata about each field including its ID
+      for (Class<?> innerClass : clazz.getDeclaredClasses()) {
+        if (isThriftFieldsEnum(innerClass)) {
+          validateAllFieldIdsInClass(innerClass, className, violations);
+          break;
+        }
+      }
+    } catch (ClassNotFoundException e) {
+      // File exists but class can't be loaded - might not be compiled
+      // or might not be a valid Thrift-generated class
+      LOGGER.error(e, "Unable to find class " + fullClassName);
+    }
+  }
+
+  /** Checks if the given class is a Thrift-generated _Fields enum that contains field metadata. */
+  private boolean isThriftFieldsEnum(Class<?> innerClass) {
+    return "_Fields".equals(innerClass.getSimpleName())
+        && innerClass.isEnum()
+        && TFieldIdEnum.class.isAssignableFrom(innerClass);
+  }
+
+  /**
+   * Validates that all field IDs in a Thrift class are within the allowed range. Reports any fields
+   * that have IDs >= MAX_ALLOWED_FIELD_ID.
+   */
+  private void validateAllFieldIdsInClass(
+      Class<?> fieldsEnum, String className, List<String> violations) {
+    Object[] fieldDefinitions = fieldsEnum.getEnumConstants();
+
+    if (fieldDefinitions != null) {
+      for (Object fieldDefinition : fieldDefinitions) {
+        TFieldIdEnum thriftField = (TFieldIdEnum) fieldDefinition;
+        short fieldId = thriftField.getThriftFieldId();
+
+        if (fieldId >= MAX_ALLOWED_FIELD_ID) {
+          String fieldName = fieldDefinition.toString();
+          violations.add(
+              String.format(
+                  "%s._Fields.%s has field ID %d (exceeds maximum of %d)",
+                  className, fieldName, fieldId, MAX_ALLOWED_FIELD_ID - 1));
+        }
+      }
+    }
+  }
+}