gson-comments/gson/src/test/java/com/google/gson/FieldNamingPolicyTest.java

/*
 * Copyright (C) 2021 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.gson;

import static com.google.common.truth.Truth.assertThat;
import static com.google.common.truth.Truth.assertWithMessage;

import com.google.gson.functional.FieldNamingTest;
import java.lang.reflect.Field;
import java.util.Locale;
import org.junit.Test;

/**
 * Performs tests directly against {@link FieldNamingPolicy}; for integration tests see {@link
 * FieldNamingTest}.
 */
public class FieldNamingPolicyTest {
  @Test
  public void testSeparateCamelCase() {
    // Map from original -> expected
    String[][] argumentPairs = {
      {"a", "a"},
      {"ab", "ab"},
      {"Ab", "Ab"},
      {"aB", "a_B"},
      {"AB", "A_B"},
      {"A_B", "A__B"},
      {"firstSecondThird", "first_Second_Third"},
      {"__", "__"},
      {"_123", "_123"}
    };

    for (String[] pair : argumentPairs) {
      assertThat(FieldNamingPolicy.separateCamelCase(pair[0], '_')).isEqualTo(pair[1]);
    }
  }

  @Test
  public void testUpperCaseFirstLetter() {
    // Map from original -> expected
    String[][] argumentPairs = {
      {"a", "A"},
      {"ab", "Ab"},
      {"AB", "AB"},
      {"_a", "_A"},
      {"_ab", "_Ab"},
      {"__", "__"},
      {"_1", "_1"},
      // Not a letter, but has uppercase variant (should not be uppercased)
      // See https://github.com/google/gson/issues/1965
      {"\u2170", "\u2170"},
      {"_\u2170", "_\u2170"},
      {"\u2170a", "\u2170A"},
    };

    for (String[] pair : argumentPairs) {
      assertThat(FieldNamingPolicy.upperCaseFirstLetter(pair[0])).isEqualTo(pair[1]);
    }
  }

  /** Upper-casing policies should be unaffected by default Locale. */
  @Test
  public void testUpperCasingLocaleIndependent() throws Exception {
    class Dummy {
      @SuppressWarnings("unused")
      int i;
    }

    FieldNamingPolicy[] policies = {
      FieldNamingPolicy.UPPER_CAMEL_CASE,
      FieldNamingPolicy.UPPER_CAMEL_CASE_WITH_SPACES,
      FieldNamingPolicy.UPPER_CASE_WITH_UNDERSCORES,
    };

    Field field = Dummy.class.getDeclaredField("i");
    String name = field.getName();
    String expected = name.toUpperCase(Locale.ROOT);

    Locale oldLocale = Locale.getDefault();
    // Set Turkish as Locale which has special case conversion rules
    Locale.setDefault(new Locale("tr"));

    try {
      // Verify that default Locale has different case conversion rules
      assertWithMessage("Test setup is broken")
          .that(name.toUpperCase(Locale.getDefault()))
          .doesNotMatch(expected);

      for (FieldNamingPolicy policy : policies) {
        // Should ignore default Locale
        assertWithMessage("Unexpected conversion for %s", policy)
            .that(policy.translateName(field))
            .matches(expected);
      }
    } finally {
      Locale.setDefault(oldLocale);
    }
  }

  /** Lower casing policies should be unaffected by default Locale. */
  @Test
  public void testLowerCasingLocaleIndependent() throws Exception {
    class Dummy {
      @SuppressWarnings({"unused", "ConstantField"})
      int I;
    }

    FieldNamingPolicy[] policies = {
      FieldNamingPolicy.LOWER_CASE_WITH_DASHES,
      FieldNamingPolicy.LOWER_CASE_WITH_DOTS,
      FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES,
    };

    Field field = Dummy.class.getDeclaredField("I");
    String name = field.getName();
    String expected = name.toLowerCase(Locale.ROOT);

    Locale oldLocale = Locale.getDefault();
    // Set Turkish as Locale which has special case conversion rules
    Locale.setDefault(new Locale("tr"));

    try {
      // Verify that default Locale has different case conversion rules
      assertWithMessage("Test setup is broken")
          .that(name.toLowerCase(Locale.getDefault()))
          .doesNotMatch(expected);

      for (FieldNamingPolicy policy : policies) {
        // Should ignore default Locale
        assertWithMessage("Unexpected conversion for %s", policy)
            .that(policy.translateName(field))
            .matches(expected);
      }
    } finally {
      Locale.setDefault(oldLocale);
    }
  }
}