ConstructorHelperGenerator를 구현한다

Author: anjeongkyun

generator-core/src/main/java/io/github/protogenerator/core/ConstructorHelperGenerator.java

@@ -0,0 +1,35 @@
+package io.github.protogenerator.core;
+
+import com.google.protobuf.DescriptorProtos;
+
+public class ConstructorHelperGenerator {
+    public String generateConstructorHelper(String protoPackage, String originalClassName, DescriptorProtos.DescriptorProto message) {
+        StringBuilder sb = new StringBuilder();
+
+        sb.append("package ").append(protoPackage).append(";\n\n");
+        sb.append("public final class ").append(originalClassName).append("Constructor {\n\n");
+
+        sb.append("    private ").append(originalClassName).append("Constructor() {}\n\n");
+
+        sb.append("    public static ").append(originalClassName).append(" from(");
+        for (int i = 0; i < message.getFieldCount(); i++) {
+            DescriptorProtos.FieldDescriptorProto field = message.getField(i);
+            sb.append(JavaTypeMapper.map(field.getType())).append(" ").append(field.getName());
+            if (i < message.getFieldCount() - 1) {
+                sb.append(", ");
+            }
+        }
+        sb.append(") {\n");
+
+        sb.append("        return ").append(originalClassName).append(".newBuilder()\n");
+        for (DescriptorProtos.FieldDescriptorProto field : message.getFieldList()) {
+            sb.append("            .set").append(StringUtil.capitalize(field.getName())).append("(").append(field.getName()).append(")\n");
+        }
+        sb.append("            .build();\n");
+        sb.append("    }\n");
+
+        sb.append("}\n");
+
+        return sb.toString();
+    }
+}

unit-tests/src/test/java/io/github/protogenerator/core/ConstructorHelperGeneratorTest.java

@@ -0,0 +1,102 @@
+package io.github.protogenerator.core;
+
+import com.google.protobuf.DescriptorProtos;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class ConstructorHelperGeneratorTest {
+
+    @Test
+    @DisplayName("returns valid constructor helper code for typical message")
+    void sut_returns_valid_constructor_helper_code() {
+        // Arrange
+        var sut = new ConstructorHelperGenerator();
+        DescriptorProtos.DescriptorProto message = DescriptorProtos.DescriptorProto.newBuilder()
+            .setName("Person")
+            .addField(DescriptorProtos.FieldDescriptorProto.newBuilder()
+                .setName("name")
+                .setType(DescriptorProtos.FieldDescriptorProto.Type.TYPE_STRING)
+                .setNumber(1)
+                .build())
+            .addField(DescriptorProtos.FieldDescriptorProto.newBuilder()
+                .setName("age")
+                .setType(DescriptorProtos.FieldDescriptorProto.Type.TYPE_INT32)
+                .setNumber(2)
+                .build())
+            .build();
+
+        // Act
+        String generated = sut.generateConstructorHelper(
+            "io.github.protogenerator.example",
+            "Person",
+            message
+        );
+
+        // Assert
+        assertAll(
+            () -> assertTrue(generated.contains("package io.github.protogenerator.example;")),
+            () -> assertTrue(generated.contains("public static Person from(String name, int age)")),
+            () -> assertTrue(generated.contains(".setName(name)")),
+            () -> assertTrue(generated.contains(".setAge(age)"))
+        );
+    }
+
+    @Test
+    @DisplayName("returns empty constructor when message has no fields")
+    void sut_returns_empty_constructor_for_empty_message() {
+        // Arrange
+        var sut = new ConstructorHelperGenerator();
+        DescriptorProtos.DescriptorProto message = DescriptorProtos.DescriptorProto.newBuilder()
+            .setName("EmptyMessage")
+            .build();
+
+        // Act
+        String generated = sut.generateConstructorHelper(
+            "io.github.protogenerator.empty",
+            "EmptyMessage",
+            message
+        );
+
+        // Assert
+        assertTrue(generated.contains("public static EmptyMessage from()"));
+        assertFalse(generated.contains(".set")); // 필드가 없으니까 set 메소드가 없어야 정상
+    }
+
+    @ParameterizedTest(name = "maps proto type {0} to java type {1}")
+    @CsvSource({
+        "TYPE_STRING, String",
+        "TYPE_INT32, int",
+        "TYPE_INT64, long",
+        "TYPE_BOOL, boolean",
+        "TYPE_FLOAT, float",
+        "TYPE_DOUBLE, double"
+    })
+    void sut_maps_proto_types_to_java_types(String protoTypeName, String expectedJavaType) {
+        // Arrange
+        var sut = new ConstructorHelperGenerator();
+        DescriptorProtos.FieldDescriptorProto.Type protoType = DescriptorProtos.FieldDescriptorProto.Type.valueOf(protoTypeName);
+        DescriptorProtos.DescriptorProto message = DescriptorProtos.DescriptorProto.newBuilder()
+            .setName("SampleMessage")
+            .addField(DescriptorProtos.FieldDescriptorProto.newBuilder()
+                .setName("field")
+                .setType(protoType)
+                .setNumber(1)
+                .build())
+            .build();
+
+        // Act
+        String generated = sut.generateConstructorHelper(
+            "io.github.protogenerator.types",
+            "SampleMessage",
+            message
+        );
+
+        // Assert
+        assertTrue(generated.contains(expectedJavaType + " field"));
+        assertTrue(generated.contains(".setField(field)"));
+    }
+}