From b082390e1950e8b41a09de8428e6044d18ba0a67 Mon Sep 17 00:00:00 2001
From: Stuart Douglas <stuart.w.douglas@gmail.com>
Date: Thu, 17 Jun 2021 15:09:21 +1000
Subject: [PATCH] Add the ability to re-use an existing native build

This allows you to deploy something you have already built.
---
 .../java/io/quarkus/deployment/pkg/NativeConfig.java | 11 +++++++++++
 .../deployment/pkg/steps/NativeImageBuildStep.java   | 12 ++++++++++--
 docs/src/main/asciidoc/container-image.adoc          |  2 ++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/core/deployment/src/main/java/io/quarkus/deployment/pkg/NativeConfig.java b/core/deployment/src/main/java/io/quarkus/deployment/pkg/NativeConfig.java
index 7717fd5d137e1..d7faf57b3842f 100644
--- a/core/deployment/src/main/java/io/quarkus/deployment/pkg/NativeConfig.java
+++ b/core/deployment/src/main/java/io/quarkus/deployment/pkg/NativeConfig.java
@@ -229,6 +229,17 @@ public class NativeConfig {
     @ConfigItem
     public boolean reportErrorsAtRuntime;
 
+    /**
+     * Don't build a native image if it already exists.
+     *
+     * This is useful if you have already built an image and you want to use Quarkus to deploy it somewhere.
+     *
+     * Note that this is not able to detect if the existing image is outdated, if you have modified source
+     * or config and want a new image you must not use this flag.
+     */
+    @ConfigItem(defaultValue = "false")
+    public boolean reuseExisting;
+
     /**
      * Build time configuration options for resources inclusion in the native executable.
      */
diff --git a/core/deployment/src/main/java/io/quarkus/deployment/pkg/steps/NativeImageBuildStep.java b/core/deployment/src/main/java/io/quarkus/deployment/pkg/steps/NativeImageBuildStep.java
index f7f4b2bb6b95c..ab0508cd11c3a 100644
--- a/core/deployment/src/main/java/io/quarkus/deployment/pkg/steps/NativeImageBuildStep.java
+++ b/core/deployment/src/main/java/io/quarkus/deployment/pkg/steps/NativeImageBuildStep.java
@@ -149,6 +149,8 @@ public NativeImageBuildItem build(NativeConfig nativeConfig, NativeImageSourceJa
 
         String nativeImageName = getNativeImageName(outputTargetBuildItem, packageConfig);
         String resultingExecutableName = getResultingExecutableName(nativeImageName, isContainerBuild);
+        Path generatedExecutablePath = outputDir.resolve(resultingExecutableName);
+        Path finalExecutablePath = outputTargetBuildItem.getOutputDirectory().resolve(resultingExecutableName);
 
         NativeImageBuildRunner buildRunner = getNativeImageBuildRunner(nativeConfig, outputDir,
                 nativeImageName, resultingExecutableName);
@@ -160,6 +162,14 @@ public NativeImageBuildItem build(NativeConfig nativeConfig, NativeImageSourceJa
         } else {
             log.error("Unable to get GraalVM version from the native-image binary.");
         }
+        if (nativeConfig.reuseExisting) {
+            if (Files.exists(finalExecutablePath)) {
+                return new NativeImageBuildItem(finalExecutablePath,
+                        new NativeImageBuildItem.GraalVMVersion(graalVMVersion.fullVersion, graalVMVersion.major,
+                                graalVMVersion.minor,
+                                graalVMVersion.distribution.name()));
+            }
+        }
 
         try {
             if (nativeConfig.cleanupServer) {
@@ -189,8 +199,6 @@ public NativeImageBuildItem build(NativeConfig nativeConfig, NativeImageSourceJa
             if (exitCode != 0) {
                 throw imageGenerationFailed(exitCode, nativeImageArgs);
             }
-            Path generatedExecutablePath = outputDir.resolve(resultingExecutableName);
-            Path finalExecutablePath = outputTargetBuildItem.getOutputDirectory().resolve(resultingExecutableName);
             IoUtils.copy(generatedExecutablePath, finalExecutablePath);
             Files.delete(generatedExecutablePath);
             if (nativeConfig.debug.enabled) {
diff --git a/docs/src/main/asciidoc/container-image.adoc b/docs/src/main/asciidoc/container-image.adoc
index 6691068a46159..0cfc429603571 100644
--- a/docs/src/main/asciidoc/container-image.adoc
+++ b/docs/src/main/asciidoc/container-image.adoc
@@ -106,6 +106,8 @@ To build a container image for your project, `quarkus.container-image.build=true
 ./mvnw clean package -Dquarkus.container-image.build=true
 ----
 
+NOTE: If you ever want to build a native container image and already have an existing native image you can set `-Dquarkus.native.reuse-existing=true` and the native image build will not be re-run.
+
 == Pushing
 
 To push a container image for your project, `quarkus.container-image.push=true` needs to be set using any of the ways that Quarkus supports.