fix: validate that contexts exists before trying to build client

Author: philippeboyd

lib/krane/kubeclient_builder.rb

@@ -135,7 +135,9 @@ def validate_config_files!
 
     def build_kubeclient(api_version:, context:, endpoint_path: nil)
       validate_config_files!
-      @kubeclient_configs ||= @kubeconfig_files.map { |f| Kubeclient::Config.read(f) }
+      @kubeclient_configs ||= @kubeconfig_files
+        .select { |f| config_has_contexts?(f) }
+        .map { |f| Kubeclient::Config.read(f) }
       # Find a context defined in kube conf files that matches the input context by name
       config = @kubeclient_configs.find { |c| c.contexts.include?(context) }
       raise ContextMissingError.new(context, @kubeconfig_files) unless config
@@ -154,5 +156,10 @@ def build_kubeclient(api_version:, context:, endpoint_path: nil)
       client.discover
       client
     end
+
+    def config_has_contexts?(file_path)
+      config = YAML.safe_load(File.read(file_path))
+      config["contexts"].is_a?(Array) && config["contexts"].any?
+    end
   end
 end

test/fixtures/kube-config/empty_config.yml

@@ -0,0 +1,7 @@
+apiVersion: v1
+clusters: null
+contexts: null
+current-context: something
+kind: Config
+preferences: {}
+users: null

test/unit/krane/kubeclient_builder_test.rb

@@ -64,4 +64,16 @@ def test_build_client_from_multiple_config_files
     assert(!client.nil?, "Expected Kubeclient is built for context " \
       "#{context_name} with success.")
   end
+
+  def test_empty_contexts_kubeconfig_file
+    # Should ignore kubeconfig files with no contexts defined
+    Kubeclient::Client.any_instance.stubs(:discover)
+    empty_config = File.join(__dir__, '../../fixtures/kube-config/empty_config.yml')
+    dummy_config = File.join(__dir__, '../../fixtures/kube-config/dummy_config.yml')
+
+    # When combined with a valid config, the empty one is silently ignored
+    kubeclient_builder = Krane::KubeclientBuilder.new(kubeconfig: "#{empty_config}:#{dummy_config}")
+    client = kubeclient_builder.build_v1_kubeclient("docker-for-desktop")
+    assert(!client.nil?, "Expected Kubeclient to be built successfully, ignoring empty config")
+  end
 end