refactor(kubernetes): Remove nested Options (#4743)

Kubernetes module was previously a bit messy, with lots of
unnecessarily nested options. Clean this up using filter_map and
find_map, with two major results:

1. `ctx_components` is now a Vec<KubeCtxComponent> instead of a
   Vec<Option<KubeCtxComponent>>. This greatly simplified downstream
   processing of these context components.

2. Instead of storing a partial computation of the namespace in
   variables `kube_ns`, etc, compute them directly in the formatter
   mapping. This is made simpler (read: actually doable) by change 1.

1 files changed, 17 insertions, 38 deletions

diff --git a/src/modules/kubernetes.rs b/src/modules/kubernetes.rs
index 6fec82d72..aa7ae9bec 100644
--- a/src/modules/kubernetes.rs
+++ b/src/modules/kubernetes.rs
@@ -34,10 +34,7 @@ fn get_kube_context(filename: path::PathBuf) -> Option<String> {
     Some(current_ctx.to_string())
 }
 
-fn get_kube_ctx_component(
-    filename: path::PathBuf,
-    current_ctx: String,
-) -> Option<KubeCtxComponents> {
+fn get_kube_ctx_component(filename: path::PathBuf, current_ctx: &str) -> Option<KubeCtxComponents> {
     let contents = utils::read_file(filename).ok()?;
 
     let yaml_docs = YamlLoader::load_from_str(&contents).ok()?;
@@ -120,7 +117,7 @@ pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
     };
 
     // If we have some config for doing the directory scan then we use it but if we don't then we
-    // assume we should treat it like the module is enabled to preserve backward compatability.
+    // assume we should treat it like the module is enabled to preserve backward compatibility.
     let have_scan_config = !(config.detect_files.is_empty()
         && config.detect_folders.is_empty()
         && config.detect_extensions.is_empty());
@@ -144,23 +141,10 @@ pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
 
     let kube_ctx = env::split_paths(&kube_cfg).find_map(get_kube_context)?;
 
-    let ctx_components: Vec<Option<KubeCtxComponents>> = env::split_paths(&kube_cfg)
-        .map(|filename| get_kube_ctx_component(filename, kube_ctx.clone()))
+    let ctx_components: Vec<KubeCtxComponents> = env::split_paths(&kube_cfg)
+        .filter_map(|filename| get_kube_ctx_component(filename, &kube_ctx))
         .collect();
 
-    let kube_user = ctx_components.iter().find(|&ctx| match ctx {
-        Some(kube) => kube.user.is_some(),
-        None => false,
-    });
-    let kube_ns = ctx_components.iter().find(|&ctx| match ctx {
-        Some(kube) => kube.namespace.is_some(),
-        None => false,
-    });
-    let kube_cluster = ctx_components.iter().find(|&ctx| match ctx {
-        Some(kube) => kube.cluster.is_some(),
-        None => false,
-    });
-
     let parsed = StringFormatter::new(config.format).and_then(|formatter| {
         formatter
             .map_meta(|variable, _| match variable {
@@ -174,25 +158,20 @@ pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
             .map(|variable| match variable {
                 "context" => Some(Ok(get_kube_context_name(&config, &kube_ctx))),
 
-                "namespace" => kube_ns.and_then(|ctx| {
-                    ctx.as_ref().map(|kube| {
-                        // unwrap is safe as kube_ns only holds kube.namespace.is_some()
-                        Ok(Cow::Borrowed(kube.namespace.as_ref().unwrap().as_str()))
-                    })
-                }),
-                "user" => kube_user.and_then(|ctx| {
-                    ctx.as_ref().map(|kube| {
-                        // unwrap is safe as kube_user only holds kube.user.is_some()
-                        Ok(get_kube_user(&config, kube.user.as_ref().unwrap().as_str()))
-                    })
-                }),
-                "cluster" => kube_cluster.and_then(|ctx| {
-                    ctx.as_ref().map(|kube| {
-                        // unwrap is safe as kube_cluster only holds kube.cluster.is_some()
-                        Ok(Cow::Borrowed(kube.cluster.as_ref().unwrap().as_str()))
-                    })
-                }),
+                "namespace" => ctx_components
+                    .iter()
+                    .find_map(|kube| kube.namespace.as_deref())
+                    .map(|namespace| Ok(Cow::Borrowed(namespace))),
+
+                "user" => ctx_components
+                    .iter()
+                    .find_map(|kube| kube.user.as_deref())
+                    .map(|user| Ok(get_kube_user(&config, user))),
 
+                "cluster" => ctx_components
+                    .iter()
+                    .find_map(|kube| kube.cluster.as_deref())
+                    .map(|cluster| Ok(Cow::Borrowed(cluster))),
                 _ => None,
             })
             .parse(None, Some(context))