Migrate to Gradle (#1159)

* Start gradle root

* Clean up test API ambiguities

These don't compile in gradle anymore and the team[] warns

* Exclude .gradle dirs in git

* Set up moshi module

* Set up moshi-adapters

* Add repositories to subprojects

* Set target/source compatibility

* Set up examples

* Fix location of reflect/test dir

* Set up moshi-kotlin

* Set up code gen

* Opportunistic update code gen deps

* Fix up with code gen

* Set up kotlin tests

* Update snapshots

* Update travis build

* Configure checkstyle

* Cache gradle

* Finish fixing up checkstyle

* Now disable checkstyle until we can fix them all :|

* Update contributing

* Fix tests in codegen

* Remove unnecessary annotation

* Remove maven stuff!

* Suppress warning

* Remove jcenter

* Consolidate dependencies

* Revert "Clean up test API ambiguities"

This reverts commit 3ead69b844b5d7f66134b721e95581f5df1cccd6.

* Fix incap dep

* Opportunistically fix some small kotlinpoet deprecations

* Automatically apply the stdlib to all kotlin projects

* Opportunistic move to opt-in and remove unnecessary annotations

The kotlin maven plugin didn't handle these well in the IDE, gradle does

* Fix Type doc warning

* Fix okio version

* Fix dokka support

* Fix copypasta

* Use new snapshot

* Kotlin 1.4.0

kotlin/codegen/build.gradle.kts

@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2020 Square, 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
+ *
+ *    https://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.
+ */
+import com.github.jengelman.gradle.plugins.shadow.tasks.ConfigureShadowRelocation
+import com.github.jengelman.gradle.plugins.shadow.transformers.ServiceFileTransformer
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+  kotlin("jvm")
+  kotlin("kapt")
+  id("com.vanniktech.maven.publish")
+  id("com.github.johnrengelman.shadow") version "5.2.0"
+}
+
+tasks.withType<KotlinCompile>().configureEach {
+  kotlinOptions {
+    jvmTarget = "1.8"
+    freeCompilerArgs = listOf(
+        "-progressive",
+        "-Xopt-in=com.squareup.kotlinpoet.metadata.KotlinPoetMetadataPreview"
+    )
+  }
+}
+
+val shade: Configuration = configurations.maybeCreate("compileShaded")
+configurations.getByName("compileOnly").extendsFrom(shade)
+dependencies {
+  implementation(project(":moshi"))
+  implementation(kotlin("reflect"))
+  shade(Dependencies.Kotlin.metadata) {
+    exclude(group = "org.jetbrains.kotlin", module = "kotlin-stdlib")
+  }
+  implementation(Dependencies.KotlinPoet.kotlinPoet)
+  shade(Dependencies.KotlinPoet.metadata) {
+    exclude(group = "org.jetbrains.kotlin")
+  }
+  shade(Dependencies.KotlinPoet.metadataSpecs) {
+    exclude(group = "org.jetbrains.kotlin")
+  }
+  shade(Dependencies.KotlinPoet.elementsClassInspector) {
+    exclude(group = "org.jetbrains.kotlin")
+  }
+  implementation(Dependencies.asm)
+
+  implementation(Dependencies.AutoService.annotations)
+  kapt(Dependencies.AutoService.processor)
+  implementation(Dependencies.Incap.annotations)
+  kapt(Dependencies.Incap.processor)
+
+  // Copy these again as they're not automatically included since they're shaded
+  testImplementation(Dependencies.KotlinPoet.metadata)
+  testImplementation(Dependencies.KotlinPoet.metadataSpecs)
+  testImplementation(Dependencies.KotlinPoet.elementsClassInspector)
+  testImplementation(Dependencies.Testing.junit)
+  testImplementation(Dependencies.Testing.assertj)
+  testImplementation(Dependencies.Testing.truth)
+  testImplementation(Dependencies.Testing.compileTesting)
+  testImplementation(Dependencies.okio2)
+}
+
+val relocateShadowJar = tasks.register<ConfigureShadowRelocation>("relocateShadowJar") {
+  target = tasks.shadowJar.get()
+}
+
+val shadowJar = tasks.shadowJar.apply {
+  configure {
+    dependsOn(relocateShadowJar)
+    archiveClassifier.set("")
+    configurations = listOf(shade)
+    relocate("com.squareup.kotlinpoet.metadata", "com.squareup.moshi.kotlinpoet.metadata")
+    relocate("com.squareup.kotlinpoet.classinspector",
+        "com.squareup.moshi.kotlinpoet.classinspector")
+    relocate("kotlinx.metadata", "com.squareup.moshi.kotlinx.metadata")
+    transformers.add(ServiceFileTransformer())
+  }
+}
+
+artifacts {
+  runtime(shadowJar)
+  archives(shadowJar)
+}
+
+// Shadow plugin doesn't natively support gradle metadata, so we have to tell the maven plugin where
+// to get a jar now.
+afterEvaluate {
+  configure<PublishingExtension> {
+    publications.withType<MavenPublication>().configureEach {
+      if (name == "pluginMaven") {
+        // This is to properly wire the shadow jar's gradle metadata and pom information
+        setArtifacts(artifacts.matching { it.classifier != "" })
+        // Ugly but artifact() doesn't support TaskProviders
+        artifact(shadowJar.get())
+      }
+    }
+  }
+}