fix: copy KUBECONFIG as defined in shell to system properties (#826)

src/main/kotlin/com/redhat/devtools/intellij/kubernetes/model/client/ClientAdapter.kt

@@ -64,6 +64,7 @@ abstract class ClientAdapter<C : KubernetesClient>(private val fabric8Client: C)
             createConfig: (context: String?) -> Config = { context -> Config.autoConfigure(context) },
             externalTrustManagerProvider: ((toIntegrate: List<X509ExtendedTrustManager>) -> X509TrustManager)? = null
         ): ClientAdapter<out KubernetesClient> {
+            KubeConfigEnvVar.copyToSystemProperties()
             val config = createConfig.invoke(context)
             setNamespace(namespace, config)
             val builder = clientBuilder ?: KubernetesClientBuilder()

src/main/kotlin/com/redhat/devtools/intellij/kubernetes/model/client/KubeConfigEnvVar.kt

@@ -0,0 +1,43 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Red Hat, Inc.
+ * Distributed under license by Red Hat, Inc. All rights reserved.
+ * This program is made available under the terms of the
+ * Eclipse Public License v2.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v20.html
+ *
+ * Contributors:
+ * Red Hat, Inc. - initial API and implementation
+ ******************************************************************************/
+package com.redhat.devtools.intellij.kubernetes.model.client
+
+import com.intellij.openapi.util.SystemInfo
+import com.intellij.util.EnvironmentUtil
+
+object KubeConfigEnvVar {
+
+    private const val KUBECONFIG_ENV_VAR = "KUBECONFIG"
+
+    /**
+     * Copies the "KUBECONFIG" env variable and it's value to the system properties.
+     * This env variable is used to list multiple config files and is supported by `kubectl`.
+     *
+     * example:
+     * ```
+     * export KUBECONFIG=${HOME}/.kube/config:${HOME}/.kube/minikube.yaml
+     * ```
+     * On MacOS env variables present in the shell are not present in IDEA
+     * because applications that are launched from the dock don't get
+     * env variables that are exported for the shell (`~/.zshrc`, `~/.bashrc`, `~/.zprofile`, etc.).
+     * Therefore they are not present in [System.getProperties].
+     * This method inspects the shell env variables and copies them over to the System properties.
+     *
+     * **See Also:** [issue #826](https://github.com/redhat-developer/intellij-kubernetes/issues/826)
+     */
+    fun copyToSystemProperties() {
+        if (SystemInfo.isMac) {
+            val kubeconfig = EnvironmentUtil.getValue(KUBECONFIG_ENV_VAR) ?: return
+            System.getProperties()[KUBECONFIG_ENV_VAR] = kubeconfig
+            System.getProperties()[KUBECONFIG_ENV_VAR.lowercase()] = kubeconfig
+        }
+    }
+}