From 7e70c93cbf6d62dbc53714e4c5b72540b84af201 Mon Sep 17 00:00:00 2001
From: Yahor Berdnikau <yahor.berdnikau@jetbrains.com>
Date: Thu, 1 Jul 2021 15:21:42 +0200
Subject: [PATCH] Allow to avoid using JDK 1.6 and JDK 1.7 in the repo.

This behaviour could be enabled via adding
'kotlin.build.isObsoleteJdkOverrideEnabled=true'
to the 'local.properties' file.

^KT-46972 Fixed
---
 ReadMe.md                                     |  4 +++
 .../src/main/kotlin/BuildPropertiesExt.kt     |  4 +++
 buildSrc/src/main/kotlin/JvmToolchain.kt      | 32 +++++++++++++------
 3 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/ReadMe.md b/ReadMe.md
index f356a69e71c..9302ab488e5 100644
--- a/ReadMe.md
+++ b/ReadMe.md
@@ -56,6 +56,10 @@ Alternatively, it is still possible to only provide required JDKs via environmen
 from environmental variables - disable Gradle toolchain auto-detection by passing `-Porg.gradle.java.installations.auto-detect=false` option
 (or put it into `$GRADLE_USER_HOME/gradle.properties`).
 
+For local development, if you're not working on bytecode generation or the standard library, it's OK to avoid installing JDK 1.6 and JDK 1.7.
+Add `kotlin.build.isObsoleteJdkOverrideEnabled=true` to the `local.properties` file, so build will only use JDK 1.8+. Note, that in this
+case, build will have Gradle remote build cache misses for some tasks. 
+
 Note: The JDK 6 for MacOS is not available on Oracle's site. You can install it by
 
 ```bash
diff --git a/buildSrc/src/main/kotlin/BuildPropertiesExt.kt b/buildSrc/src/main/kotlin/BuildPropertiesExt.kt
index 3adb3ddfff8..c02f7ae5c2d 100644
--- a/buildSrc/src/main/kotlin/BuildPropertiesExt.kt
+++ b/buildSrc/src/main/kotlin/BuildPropertiesExt.kt
@@ -20,3 +20,7 @@ val KotlinBuildProperties.jarCompression: Boolean get() = getBoolean("kotlin.bui
 val KotlinBuildProperties.ignoreTestFailures: Boolean get() = getBoolean("ignoreTestFailures", isTeamcityBuild)
 
 val KotlinBuildProperties.disableWerror: Boolean get() = getBoolean("kotlin.build.disable.werror", false)
+
+val KotlinBuildProperties.isObsoleteJdkOverrideEnabled: Boolean
+    get() = !isTeamcityBuild &&
+            getBoolean("kotlin.build.isObsoleteJdkOverrideEnabled", false)
diff --git a/buildSrc/src/main/kotlin/JvmToolchain.kt b/buildSrc/src/main/kotlin/JvmToolchain.kt
index cb46d15d4bb..5c629a1fabe 100644
--- a/buildSrc/src/main/kotlin/JvmToolchain.kt
+++ b/buildSrc/src/main/kotlin/JvmToolchain.kt
@@ -10,16 +10,18 @@ import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 enum class JdkMajorVersion(
     val majorVersion: Int,
+    val targetName: String = majorVersion.toString(),
+    val overrideMajorVersion: Int? = null,
     private val mandatory: Boolean = true
 ) {
-    JDK_1_6(6),
-    JDK_1_7(7),
-    JDK_1_8(8),
+    JDK_1_6(6, targetName = "1.6", overrideMajorVersion = 8),
+    JDK_1_7(7, targetName = "1.7", overrideMajorVersion = 8),
+    JDK_1_8(8, targetName = "1.8"),
     JDK_9(9),
-    JDK_10(10, false),
-    JDK_11(11, false),
-    JDK_15(15, false),
-    JDK_16(16, false);
+    JDK_10(10, mandatory = false),
+    JDK_11(11, mandatory = false),
+    JDK_15(15, mandatory = false),
+    JDK_16(16, mandatory = false);
 
     fun isMandatory(): Boolean = mandatory
 }
@@ -34,9 +36,19 @@ fun Project.configureJvmToolchain(
     plugins.withId("org.jetbrains.kotlin.jvm") {
         val kotlinExtension = extensions.getByType<KotlinTopLevelExtension>()
 
-        kotlinExtension.jvmToolchain {
-            (this as JavaToolchainSpec).languageVersion
-                .set(JavaLanguageVersion.of(jdkVersion.majorVersion))
+        if (project.kotlinBuildProperties.isObsoleteJdkOverrideEnabled &&
+            jdkVersion.overrideMajorVersion != null
+        ) {
+            kotlinExtension.jvmToolchain {
+                (this as JavaToolchainSpec).languageVersion
+                    .set(JavaLanguageVersion.of(jdkVersion.overrideMajorVersion))
+            }
+            updateJvmTarget(jdkVersion.targetName)
+        } else {
+            kotlinExtension.jvmToolchain {
+                (this as JavaToolchainSpec).languageVersion
+                    .set(JavaLanguageVersion.of(jdkVersion.majorVersion))
+            }
         }
 
         tasks