Version constant injection

buildSrc/src/main/kotlin/Projects.kt

@@ -1,11 +1,24 @@
-import org.gradle.kotlin.dsl.DependencyHandlerScope
-import org.gradle.kotlin.dsl.project
+import org.gradle.api.Project
+import java.io.ByteArrayOutputStream
 
 /**
  * whether the process has been invoked by JitPack
  */
 val isJitPack get() = "true" == System.getenv("JITPACK")
 
+val Project.commitHash: String
+    get() = try {
+        ByteArrayOutputStream().use { out ->
+            exec {
+                commandLine("git", "rev-parse", "--short", "HEAD")
+                standardOutput = out
+            }
+            out.toString().trim()
+        }
+    } catch (e: Throwable) {
+        System.getenv("GITHUB_SHA") ?: "unknown"
+    }
+
 object Library {
     const val name = "kord"
     const val group = "dev.kord"

common/build.gradle.kts

@@ -1,7 +1,16 @@
+buildscript {
+    repositories {
+        mavenCentral()
+    }
+}
+
 plugins {
     `kord-module`
     `kord-sampled-module`
     `kord-publishing`
+
+    // see https://github.com/gmazzo/gradle-buildconfig-plugin
+    id("com.github.gmazzo.buildconfig") version "3.0.3"
 }
 
 dependencies {
@@ -11,3 +20,24 @@ dependencies {
     testImplementation(libs.bundles.test.implementation)
     testRuntimeOnly(libs.bundles.test.runtime)
 }
+
+/*
+This will generate a file named "BuildConfigGenerated.kt" that looks like:
+
+package dev.kord.common
+
+internal const val BUILD_CONFIG_GENERATED_LIBRARY_VERSION: String = "<version>"
+internal const val BUILD_CONFIG_GENERATED_COMMIT_HASH: String = "<commit hash>"
+*/
+buildConfig {
+    packageName("dev.kord.common")
+    className("BuildConfigGenerated")
+
+    useKotlinOutput {
+        topLevelConstants = true
+        internalVisibility = true
+    }
+
+    buildConfigField(type = "String", name = "BUILD_CONFIG_GENERATED_LIBRARY_VERSION", value = "\"${Library.version}\"")
+    buildConfigField(type = "String", name = "BUILD_CONFIG_GENERATED_COMMIT_HASH", value = "\"$commitHash\"")
+}

common/src/main/kotlin/KordConstants.kt

@@ -1,7 +1,19 @@
+// No const vals, they are inlined, so recompiling would be required when values change.
+@file:Suppress("MayBeConstant")
+
 package dev.kord.common
 
 public object KordConstants {
 
+    /** Kord's version. */
+    public val KORD_VERSION: String = BUILD_CONFIG_GENERATED_LIBRARY_VERSION
+
+    /** The hash of the commit from which this Kord version was built. */
+    public val KORD_COMMIT_HASH: String = BUILD_CONFIG_GENERATED_COMMIT_HASH
+
+    /** URL for Kord's GitHub repository. */
+    public val KORD_GITHUB_URL: String = "https://github.com/kordlib/kord"
+
     /** Kord's value for the [User Agent header](https://discord.com/developers/docs/reference#user-agent). */
-    public const val USER_AGENT: String = "DiscordBot (https://github.com/kordlib/kord, 0.8.0-M12)"
+    public val USER_AGENT: String = "DiscordBot ($KORD_GITHUB_URL, $KORD_VERSION)"
 }