support :never for resource-refresh-overrides (#177)

Contributes to #172.

docs/how-tos/customization.md

@@ -58,6 +58,44 @@ the `kele-get` result buffer's keybindings.
 Kele provides a handful of customization variables with which you can influence [cache
 behavior](../explanations/design.md#caches).
 
+### Changing resource caching expiration time
+
+!!! note
+
+    Currently only namespace names are cached.
+
+Kele caches certain resource names upon fetching. This speeds up subsequent
+queries drastically.
+
+These cached values have a expiration time, after which the cached values are
+erased.
+
+You can change the default refresh interval with
+`kele-resource-default-refresh-interval`. For example, a value of `60` means
+that all cached values are erased 60 seconds after creation.
+
+### Changing resource-specific caching expiration time
+
+For some resources, you might expect the set of names in the cluster to change
+more or less frequently than others. Some you might, for all intents and
+purposes, assume **never** change.
+
+You can set resource-specific cache expirations with
+`kele-resource-refresh-overrides`. For example, the following will set cached
+names for Pods to expire after 600 seconds:
+
+```emacs-lisp
+(setq kele-resource-refresh-overrides '((pod . 600)))
+```
+
+You can **also** set the special value `:never`, in which case the cached values
+are **never** automatically erased once they're written. For example, the
+following will set cached names for Namespaces to never expire:
+
+```emacs-lisp
+(setq kele-resource-refresh-overrides '((namespace . :never)))
+```
+
 ### Change the discovery cache polling interval
 
 If you'd like Kele to poll the discovery cache more or less frequently than the default, set

docs/references/changelog.md

@@ -17,6 +17,8 @@ versioning][semver].
   **Kubernetes** section on the menu bar
 - Added ability to switch contexts from within the menu bar; available contexts
   are shown as a sub-menu
+- Added ability to specify that cached names of a specific resource should never
+  expire
 
 ### Fixed
 

kele.el

@@ -82,9 +82,14 @@ If a resource is listed here, the corresponding value will be
 used for cache time-to-live for that resource.  Otherwise,
 `kele-resource-default-refresh-interval' is used.
 
+If the value is :never, then the resource will be cached once and
+then never expired.
+
 Keys are the singular form of the resource name, e.g. \"pod\" for
 pods."
-  :type '(alist :key-type symbol :value-type 'integer)
+  :type '(alist :key-type symbol :value-type (radio
+                                              (integer :tag "Expiration duration in seconds")
+                                              (const :tag "Never expire once cached" :never)))
   :group 'kele)
 
 (defcustom kele-discovery-refresh-interval
@@ -821,11 +826,13 @@ The cache has a TTL as defined by
 
 Returns the passed-in list of namespaces."
   (add-to-list 'kele--namespaces-cache `(,(intern context) . ,namespace-names))
-  (run-with-timer
-   (kele--get-cache-ttl-for-resource 'namespace)
-   nil
-   #'kele--clear-namespaces-for-context
-   context)
+  (let ((ttl (kele--get-cache-ttl-for-resource 'namespace)))
+    (when (and ttl (not (eq ttl :never)))
+      (run-with-timer
+       (kele--get-cache-ttl-for-resource 'namespace)
+       nil
+       #'kele--clear-namespaces-for-context
+       context)))
   namespace-names)
 
 (cl-defstruct (kele--resource-container

tests/unit/test-kele.el

@@ -176,7 +176,15 @@
 (describe "kele--cache-namespaces"
   (before-each
     (spy-on 'run-with-timer)
-    (setq kele--namespaces-cache nil))
+    (setq kele--namespaces-cache nil)
+    (setq kele-resource-refresh-overrides nil))
+
+  (describe "when resource's cache TTL is set to :never"
+    (before-each
+      (setq kele-resource-refresh-overrides '((namespace . :never))))
+    (it "does not create a timer"
+      (kele--cache-namespaces "foobar" "n0")
+      (expect 'run-with-timer :not :to-have-been-called)))
 
   (it "adds namespaces correctly"
     (kele--cache-namespaces "foobar" "n0" "n1" "n2")
@@ -191,14 +199,16 @@
 (describe "resource caching"
   (before-each
     (setq kele-resource-default-refresh-interval 60)
-    (setq kele-resource-refresh-overrides '((foo . 999))))
+    (setq kele-resource-refresh-overrides '((foo . 999)
+                                            (bar . :never))))
 
   (describe "when a resource has a TTL override"
     (it "uses the override value"
+      (expect (kele--get-cache-ttl-for-resource 'bar) :to-equal :never)
       (expect (kele--get-cache-ttl-for-resource 'foo) :to-equal 999)))
   (describe "when a resource has no TTL override"
     (it "uses the default value"
-      (expect (kele--get-cache-ttl-for-resource 'bar) :to-equal 60))))
+      (expect (kele--get-cache-ttl-for-resource 'qux) :to-equal 60))))
 
 (describe "kele--cache-update (kele--discovery-cache)"
   (describe "the retval"