client-gen: intro watchList

staging/src/k8s.io/code-generator/cmd/client-gen/generators/generator_for_type.go

@@ -172,7 +172,10 @@ func (g *genClientForType) GenerateType(c *generator.Context, t *types.Type, w i
 		"RESTClientInterface":              c.Universe.Type(types.Name{Package: "k8s.io/client-go/rest", Name: "Interface"}),
 		"schemeParameterCodec":             c.Universe.Variable(types.Name{Package: path.Join(g.clientsetPackage, "scheme"), Name: "ParameterCodec"}),
 		"jsonMarshal":                      c.Universe.Type(types.Name{Package: "encoding/json", Name: "Marshal"}),
+		"resourceVersionMatchNotOlderThan": c.Universe.Type(types.Name{Package: "k8s.io/apimachinery/pkg/apis/meta/v1", Name: "ResourceVersionMatchNotOlderThan"}),
 		"CheckListFromCacheDataConsistencyIfRequested":      c.Universe.Function(types.Name{Package: "k8s.io/client-go/util/consistencydetector", Name: "CheckListFromCacheDataConsistencyIfRequested"}),
+		"CheckWatchListFromCacheDataConsistencyIfRequested": c.Universe.Function(types.Name{Package: "k8s.io/client-go/util/consistencydetector", Name: "CheckWatchListFromCacheDataConsistencyIfRequested"}),
+		"PrepareWatchListOptionsFromListOptions":            c.Universe.Function(types.Name{Package: "k8s.io/client-go/util/watchlist", Name: "PrepareWatchListOptionsFromListOptions"}),
 	}
 
 	if generateApply {
@@ -225,6 +228,7 @@ func (g *genClientForType) GenerateType(c *generator.Context, t *types.Type, w i
 	if tags.HasVerb("list") {
 		sw.Do(listTemplate, m)
 		sw.Do(privateListTemplate, m)
+		sw.Do(watchListTemplate, m)
 	}
 	if tags.HasVerb("watch") {
 		sw.Do(watchTemplate, m)
@@ -301,6 +305,7 @@ func (g *genClientForType) GenerateType(c *generator.Context, t *types.Type, w i
 			} else {
 				sw.Do(adjustTemplate(e.VerbName, e.VerbType, listTemplate), m)
 				sw.Do(adjustTemplate(e.VerbName, e.VerbType, privateListTemplate), m)
+				sw.Do(adjustTemplate(e.VerbName, e.VerbType, watchListTemplate), m)
 			}
 		}
 
@@ -461,13 +466,22 @@ func new$.type|publicPlural$(c *$.GroupGoName$$.Version$Client) *$.type|privateP
 `
 var listTemplate = `
 // List takes label and field selectors, and returns the list of $.resultType|publicPlural$ that match those selectors.
-func (c *$.type|privatePlural$) List(ctx context.Context, opts $.ListOptions|raw$) (result *$.resultType|raw$List, err error) {
+func (c *$.type|privatePlural$) List(ctx context.Context, opts $.ListOptions|raw$) (*$.resultType|raw$List, error) {
-    defer func() {
+    if watchListOptions, hasWatchListOptionsPrepared, watchListOptionsErr  := $.PrepareWatchListOptionsFromListOptions|raw$(opts); watchListOptionsErr  != nil {
+        klog.Warningf("Failed preparing watchlist options for $.type|resource$, falling back to the standard LIST semantics, err = %v", watchListOptionsErr )
+    } else if hasWatchListOptionsPrepared {
+        result, err := c.watchList(ctx, watchListOptions)
+        if err == nil {
+            $.CheckWatchListFromCacheDataConsistencyIfRequested|raw$(ctx, "watchlist request for $.type|resource$", c.list, opts, result)
+            return result, nil
+        }
+        klog.Warningf("The watchlist request for $.type|resource$ ended with an error, falling back to the standard LIST semantics, err = %v", err)
+    }
+    result, err := c.list(ctx, opts)
     if err == nil {
         $.CheckListFromCacheDataConsistencyIfRequested|raw$(ctx, "list request for $.type|resource$", c.list, opts, result)
     }
-    }()
+    return result, err
-    return c.list(ctx, opts)
 }
 `
 
@@ -673,6 +687,25 @@ func (c *$.type|privatePlural$) Watch(ctx context.Context, opts $.ListOptions|ra
 }
 `
 
+var watchListTemplate = `
+// watchList establishes a watch stream with the server and returns the list of $.resultType|publicPlural$
+func (c *$.type|privatePlural$) watchList(ctx context.Context, opts $.ListOptions|raw$) (result *$.resultType|raw$List, err error) {
+	var timeout time.Duration
+	if opts.TimeoutSeconds != nil{
+		timeout = time.Duration(*opts.TimeoutSeconds) * time.Second
+	}
+    result = &$.resultType|raw$List{}
+	err = c.client.Get().
+		$if .namespaced$Namespace(c.ns).$end$
+		Resource("$.type|resource$").
+		VersionedParams(&opts, $.schemeParameterCodec|raw$).
+		Timeout(timeout).
+		WatchList(ctx).
+        Into(result)
+    return
+}
+`
+
 var patchTemplate = `
 // Patch applies the patch and returns the patched $.resultType|private$.
 func (c *$.type|privatePlural$) Patch(ctx context.Context, name string, pt $.PatchType|raw$, data []byte, opts $.PatchOptions|raw$, subresources ...string) (result *$.resultType|raw$, err error) {