Read type mappings from a custom dgs.codegen.typemappings file for dependencies (#735)

* Read type mappings from a dgs.codegen.typemappings file for dependencies containing schemas.

* Clean up and refactor code based on feedback.

* Add tests.

Author: srinivasankavitha

graphql-dgs-codegen-core/src/main/kotlin/com/netflix/graphql/dgs/codegen/CodeGen.kt

@@ -35,21 +35,7 @@ import com.squareup.javapoet.JavaFile
 import com.squareup.javapoet.TypeSpec
 import com.squareup.kotlinpoet.FileSpec
 import com.squareup.kotlinpoet.KModifier
-import graphql.language.Definition
-import graphql.language.DirectivesContainer
-import graphql.language.Document
-import graphql.language.EnumTypeDefinition
-import graphql.language.FieldDefinition
-import graphql.language.InputObjectTypeDefinition
-import graphql.language.InterfaceTypeDefinition
-import graphql.language.NamedNode
-import graphql.language.ObjectTypeDefinition
-import graphql.language.ObjectTypeExtensionDefinition
-import graphql.language.ScalarTypeDefinition
-import graphql.language.Type
-import graphql.language.TypeDefinition
-import graphql.language.TypeName
-import graphql.language.UnionTypeDefinition
+import graphql.language.*
 import graphql.parser.InvalidSyntaxException
 import graphql.parser.MultiSourceReader
 import graphql.parser.Parser
@@ -63,6 +49,8 @@ import java.io.Reader
 import java.lang.annotation.RetentionPolicy
 import java.nio.file.Path
 import java.nio.file.Paths
+import java.util.*
+import java.util.jar.JarFile
 import java.util.zip.ZipFile
 import javax.lang.model.element.Modifier
 import com.squareup.kotlinpoet.AnnotationSpec as KAnnotationSpec
@@ -83,6 +71,8 @@ class CodeGen(private val config: CodeGenConfig) {
     )
 
     fun generate(): CodeGenResult {
+        loadTypeMappingsFromDependencies()
+
         val codeGenResult = when (config.language) {
             Language.JAVA -> generateJava()
             Language.KOTLIN -> generateKotlin()
@@ -156,9 +146,30 @@ class CodeGen(private val config: CodeGenConfig) {
                 }
             }
         }
+
         return document
     }
 
+    private fun loadTypeMappingsFromDependencies() {
+        // process type mappings from dependencies
+        config.schemaJarFilesFromDependencies.forEach { file ->
+            JarFile(file).use { jarFile ->
+                val typeMappingsFile = jarFile.getJarEntry("META-INF/dgs.codegen.typemappings")
+                if (typeMappingsFile != null) {
+                    jarFile.getInputStream(typeMappingsFile).use { typeMappingInput ->
+                        val props = Properties()
+                        props.load(typeMappingInput)
+
+                        // Add the new type mappings from dependencies to existing type mappings.
+                        // The user provided config overrides mappings from the dependencies.
+                        @Suppress("UNCHECKED_CAST")
+                        config.typeMapping = (props as Map<String, String>).plus(config.typeMapping)
+                    }
+                }
+            }
+        }
+    }
+
     /**
      * Loads the given [MultiSourceReader.Builder] references with the sources that will be used to provide
      * the schema information for the parser.

graphql-dgs-codegen-core/src/test/kotlin/com/netflix/graphql/dgs/codegen/CodeGenTest.kt

@@ -42,6 +42,7 @@ import org.junit.jupiter.params.provider.ArgumentsSource
 import org.junit.jupiter.params.provider.MethodSource
 import org.junit.jupiter.params.provider.ValueSource
 import java.io.Serializable
+import java.nio.file.Paths
 import java.util.stream.Stream
 
 class CodeGenTest {
@@ -4990,4 +4991,53 @@ It takes a title and such.
             "com.netflix.graphql.dgs.codegen.tests.generated.types.com.netflix.graphql.dgs.codegen.tests.generated.types.B"
         )
     }
+
+    @Test
+    fun `Codegen should pick up type mappings for schema from JAR files in dependencies`() {
+        val typeMappingDependency = Paths.get("src/test/resources/dependencies/testDependency.jar").toAbsolutePath().toFile()
+        val schema = """
+            type Query {
+                person: Person
+            }
+            scalar BigDecimal 
+            
+            type Person {
+                firstname: String
+                data: BigDecimal
+            }
+        """.trimIndent()
+
+        val result = CodeGen(
+            CodeGenConfig(
+                schemas = setOf(schema),
+                schemaJarFilesFromDependencies = listOf(typeMappingDependency)
+            )
+        ).generate()
+        assertThat(result.javaDataTypes[0].typeSpec.fieldSpecs[1].type.toString() == "java.math.BigDecimal")
+    }
+
+    @Test
+    fun `Codegen should use user specfied typemappings to override type mappings from typemappings in dependencies`() {
+        val typeMappingDependency = Paths.get("src/test/resources/dependencies/testDependency.jar").toAbsolutePath().toFile()
+        val schema = """
+            type Query {
+                person: Person
+            }
+            scalar BigDecimal 
+            
+            type Person {
+                firstname: String
+                data: BigDecimal
+            }
+        """.trimIndent()
+
+        val result = CodeGen(
+            CodeGenConfig(
+                schemas = setOf(schema),
+                schemaJarFilesFromDependencies = listOf(typeMappingDependency),
+                typeMapping = mapOf("BigDecimal" to "java.lang.String")
+            )
+        ).generate()
+        assertThat(result.javaDataTypes[0].typeSpec.fieldSpecs[1].type.toString() == "java.lang.String")
+    }
 }

graphql-dgs-codegen-core/src/test/resources/dependencies/META-INF/dgs.codegen.typemappings

@@ -0,0 +1 @@
+BigDecimal:java.math.BigDecimal