feat: support extracting var from key from secret/configmap

Fixes quarkusio#9629

docs/src/main/asciidoc/deploying-to-kubernetes.adoc

@@ -214,7 +214,7 @@ NOTE: When using the `quarkus-container-image-jib` extension to build a containe
 
 Out of the box, the generated resources will be annotated with version control related information that can be used either by tooling, or by the user for troubleshooting purposes.
 
-[source, json]
+[source,json]
 ----
   "annotations": {
     "app.quarkus.io/vcs-url" : "<some url>",
@@ -224,29 +224,29 @@ Out of the box, the generated resources will be annotated with version control r
 
 ==== Custom Annotations
 
-Custom annotations can be added in a way similar to labels. For example to add the annotation `foo=bar` and `app.quarkus/id=42` just apply the following configuration:
-
+Custom annotations can be added in a way similar to labels.For example to add the annotation `foo=bar` and `app.quarkus/id=42` just apply the following configuration:
 
 [source]
 ----
 quarkus.kubernetes.annotations.foo=bar
 quarkus."app.quarkus/id"=42
 ----
 
+[#env-vars]
 ==== Environment variables
 
 Kubernetes provides multiple ways of defining environment variables:
 
 - key/value pairs
-- from a Secret
-- from a ConfigMap
-- from fields
+- import all values from a Secret or ConfigMap
+- interpolate a single value identified by a given field in a Secret or ConfigMap
+- interpolate a value from a field within the same resource
 
 ===== Environment variables from key/value pairs
 
 To add a key/value pair as an environment variable in the generated resources:
 
-[source]
+[source,properties]
 ----
 quarkus.kubernetes.env.vars.my-env-var=foobar
 ----
@@ -259,25 +259,93 @@ Please note that the key `my-env-var` will be converted to uppercase and dashes
 To add all key/value pairs of `Secret` as environment variables just apply the following configuration, separating each `Secret`
 to be used as source by a comma (`,`):
 
-[source]
+[source,properties]
 ----
 quarkus.kubernetes.env.secrets=my-secret,my-other-secret
 ----
 
+which would generate the following in the container definition:
+
+[source,yaml]
+----
+envFrom:
+  - secretRef:
+      name: my-secret
+      optional: false
+  - secretRef:
+      name: my-other-secret
+      optional: false
+----
+
+The following extracts a value identified by the `keyName` field from the `my-secret` Secret into a `foo` environment variable:
+
+[source,properties]
+----
+quarkus.kubernetes.env.mapping.foo.from-secret=my-secret
+quarkus.kubernetes.env.mapping.foo.with-key=keyName
+----
+
+This would generate the following in the `env` section of your container:
+
+[source,yaml]
+----
+- env:
+  - name: FOO
+    valueFrom:
+      secretKeyRef:
+        key: keyName
+        name: my-secret
+        optional: false
+----
+
 ===== Environment variables from ConfigMap
 
 To add all key/value pairs from `ConfigMap` as environment variables just apply the following configuration, separating each
 `ConfigMap` to be used as source by a comma (`,`):
 
-[source]
+[source,properties]
 ----
 quarkus.kubernetes.env.configmaps=my-config-map,another-config-map
 ----
 
+which would generate the following in the container definition:
+
+[source,yaml]
+----
+envFrom:
+  - configMapRef:
+      name: my-config-map
+      optional: false
+  - configMapRef:
+      name: another-config-map
+      optional: false
+----
+
+The following extracts a value identified by the `keyName` field from the `my-config-map` ConfigMap into a `foo`
+environment variable:
+
+[source,properties]
+----
+quarkus.kubernetes.env.mapping.foo.from-configmap=my-configmap
+quarkus.kubernetes.env.mapping.foo.with-key=keyName
+----
+
+This would generate the following in the `env` section of your container:
+
+[source,yaml]
+----
+- env:
+  - name: FOO
+    valueFrom:
+      configMapRefKey:
+        key: keyName
+        name: my-configmap
+        optional: false
+----
+
 ===== Environment variables from fields
 
-It's also possible to use the value from another field to add a new environment variable by specifying the path of the field to
-be used as a source, as follows:
+It's also possible to use the value from another field to add a new environment variable by specifying the path of the field to be used as a source, as follows:
 
 [source]
 ----
@@ -286,29 +354,30 @@ quarkus.kubernetes.env.fields.foo=metadata.name
 
 ===== Validation
 
-A conflict between two definitions, e.g. mistakenly assigning both a value and specifying that a variable is derived
-from a field, will result in an error being thrown at build time so that you get the opportunity to fix the issue before you
-deploy your application to your cluster where it might be more difficult to diagnose the source of the issue.
+A conflict between two definitions, e.g. mistakenly assigning both a value and specifying that a variable is derived from a field, will result in an error being thrown at build time so that you get the opportunity to fix the issue before you deploy your application to your cluster where it might be more difficult to diagnose the source of the issue.
 
-Similarly, two redundant definitions, e.g. defining an injection from the same secret twice, will not cause an issue but will
-indeed report a warning to let you know that you might not have intended to duplicate that definition.
+Similarly, two redundant definitions, e.g. defining an injection from the same secret twice, will not cause an issue but will indeed report a warning to let you know that you might not have intended to duplicate that definition.
 
+[#env-vars-backwards]
 ===== Backwards compatibility
 
-Previous versions of the Kubernetes extension supported a different syntax to add environment variables. The older syntax is
-still supported but is deprecated and it's advised that you migrate to the new syntax.
+Previous versions of the Kubernetes extension supported a different syntax to add environment variables.The older syntax is still supported but is deprecated and it's advised that you migrate to the new syntax.
 
 .Old vs. new syntax
 |====
-|                       |Old                                                    | New                                                 |
-| Plain variable        |`quarkus.kubernetes.env-vars.my-env-var.value=foobar`  | `quarkus.kubernetes.env.vars.my-env-var=foobar`     |
-| From field            |`quarkus.kubernetes.env-vars.my-env-var.field=foobar`  | `quarkus.kubernetes.env.fields.my-env-var=foobar`   |
-| All from `ConfigMap`  |`quarkus.kubernetes.env-vars.xxx.configmap=foobar`     | `quarkus.kubernetes.env.configmaps=foobar`          |
-| All from `Secret`     |`quarkus.kubernetes.env-vars.xxx.secret=foobar`        | `quarkus.kubernetes.env.secrets=foobar`             |
+|                               |Old                                                    | New                                                 |
+| Plain variable                |`quarkus.kubernetes.env-vars.my-env-var.value=foobar`  | `quarkus.kubernetes.env.vars.my-env-var=foobar`     |
+| From field                    |`quarkus.kubernetes.env-vars.my-env-var.field=foobar`  | `quarkus.kubernetes.env.fields.my-env-var=foobar`   |
+| All from `ConfigMap`          |`quarkus.kubernetes.env-vars.xxx.configmap=foobar`     | `quarkus.kubernetes.env.configmaps=foobar`          |
+| All from `Secret`             |`quarkus.kubernetes.env-vars.xxx.secret=foobar`        | `quarkus.kubernetes.env.secrets=foobar`             |
+| From one `Secret` field       |`quarkus.kubernetes.env-vars.foo.secret=foobar`        | `quarkus.kubernetes.env.mapping.foo.from-secret=foobar` |
+|                               |`quarkus.kubernetes.env-vars.foo.value=field`          | `quarkus.kubernetes.env.mapping.foo.with-key=field` |
+| From one `ConfigMap` field    |`quarkus.kubernetes.env-vars.foo.configmap=foobar`     | `quarkus.kubernetes.env.mapping.foo.from-configmap=foobar` |
+|                               |`quarkus.kubernetes.env-vars.foo.value=field`          | `quarkus.kubernetes.env.mapping.foo.with-key=field` |
 |====
 
 NOTE: If you redefine the same variable using the new syntax while keeping the old syntax, **ONLY** the new version will be kept
-and a warning will be issued to alert you of the problem. For example, if you define both
+and a warning will be issued to alert you of the problem.For example, if you define both
 `quarkus.kubernetes.env-vars.my-env-var.value=foobar` and `quarkus.kubernetes.env.vars.my-env-var=newValue`, the extension will
 only generate an environment variable `MY_ENV_VAR=newValue` and issue a warning.
 
@@ -829,7 +898,10 @@ kubernetes.env-vars[0].configmap=my-configmap
 quarkus.kubernetes.env-vars.foo.configmap=myconfigmap
 ----
 
+==== `env-vars` properties
 
+`quarkus.kubernetes.env-vars` are deprecated (though still currently supported as of this writing) and the new declaration style should be used instead.
+See <<#env-vars>> and more specifically <<env-vars-backwards>> for more details.
 
 == Deployment
 

extensions/container-image/container-image-s2i/deployment/src/main/java/io/quarkus/container/image/s2i/deployment/S2iProcessor.java

@@ -1,21 +1,10 @@
 package io.quarkus.container.image.s2i.deployment;
 
-import java.io.BufferedReader;
-import java.io.ByteArrayInputStream;
-import java.io.Closeable;
-import java.io.File;
-import java.io.IOException;
-import java.io.InputStreamReader;
+import java.io.*;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
-import java.util.Optional;
+import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executor;
 import java.util.concurrent.Executors;
@@ -55,11 +44,7 @@
 import io.quarkus.deployment.builditem.CapabilityBuildItem;
 import io.quarkus.deployment.builditem.GeneratedFileSystemResourceBuildItem;
 import io.quarkus.deployment.pkg.PackageConfig;
-import io.quarkus.deployment.pkg.builditem.ArtifactResultBuildItem;
-import io.quarkus.deployment.pkg.builditem.CurateOutcomeBuildItem;
-import io.quarkus.deployment.pkg.builditem.JarBuildItem;
-import io.quarkus.deployment.pkg.builditem.NativeImageBuildItem;
-import io.quarkus.deployment.pkg.builditem.OutputTargetBuildItem;
+import io.quarkus.deployment.pkg.builditem.*;
 import io.quarkus.deployment.pkg.steps.NativeBuild;
 import io.quarkus.kubernetes.client.deployment.KubernetesClientErrorHanlder;
 import io.quarkus.kubernetes.client.spi.KubernetesClientBuildItem;
@@ -108,11 +93,11 @@ public void s2iRequirementsJvm(S2iConfig s2iConfig,
         builderImageProducer.produce(new BaseImageInfoBuildItem(s2iConfig.baseJvmImage));
         Optional<S2iBaseJavaImage> baseImage = S2iBaseJavaImage.findMatching(s2iConfig.baseJvmImage);
         baseImage.ifPresent(b -> {
-            envProducer.produce(new KubernetesEnvBuildItem(b.getJarEnvVar(), pathToJar, OPENSHIFT));
-            envProducer.produce(new KubernetesEnvBuildItem(b.getJarLibEnvVar(),
+            envProducer.produce(KubernetesEnvBuildItem.createSimpleVar(b.getJarEnvVar(), pathToJar, OPENSHIFT));
+            envProducer.produce(KubernetesEnvBuildItem.createSimpleVar(b.getJarLibEnvVar(),
                     concatUnixPaths(jarDirectory, "lib"), OPENSHIFT));
-            envProducer.produce(new KubernetesEnvBuildItem(b.getClasspathEnvVar(), classpath, OPENSHIFT));
-            envProducer.produce(new KubernetesEnvBuildItem(b.getJvmOptionsEnvVar(),
+            envProducer.produce(KubernetesEnvBuildItem.createSimpleVar(b.getClasspathEnvVar(), classpath, OPENSHIFT));
+            envProducer.produce(KubernetesEnvBuildItem.createSimpleVar(b.getJvmOptionsEnvVar(),
                     String.join(" ", s2iConfig.jvmArguments), OPENSHIFT));
         });
 
@@ -150,9 +135,11 @@ public void s2iRequirementsNative(S2iConfig s2iConfig,
         builderImageProducer.produce(new BaseImageInfoBuildItem(s2iConfig.baseNativeImage));
         Optional<S2iBaseNativeImage> baseImage = S2iBaseNativeImage.findMatching(s2iConfig.baseNativeImage);
         baseImage.ifPresent(b -> {
-            envProducer.produce(new KubernetesEnvBuildItem(b.getHomeDirEnvVar(), s2iConfig.nativeBinaryDirectory, OPENSHIFT));
-            envProducer.produce(new KubernetesEnvBuildItem(b.getOptsEnvVar(),
-                    String.join(" ", s2iConfig.nativeArguments), OPENSHIFT));
+            envProducer.produce(
+                    KubernetesEnvBuildItem.createSimpleVar(b.getHomeDirEnvVar(), s2iConfig.nativeBinaryDirectory, OPENSHIFT));
+            envProducer.produce(
+                    KubernetesEnvBuildItem.createSimpleVar(b.getOptsEnvVar(), String.join(" ", s2iConfig.nativeArguments),
+                            OPENSHIFT));
         });
 
         if (!baseImage.isPresent()) {