[WIP] PoC implementation for HIP suggesting `warn` template function

Signed-off-by: Philipp Stehle <philipp.stehle@sap.com>

cmd/helm/template.go

@@ -168,6 +168,10 @@ func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 				}
 			}
 
+			for _, warn := range rel.Warnings {
+				warning(warn.Message)
+			}
+
 			return err
 		},
 	}

pkg/action/action.go

@@ -101,19 +101,20 @@ type Configuration struct {
 //
 // TODO: This function is badly in need of a refactor.
 // TODO: As part of the refactor the duplicate code in cmd/helm/template.go should be removed
-//       This code has to do with writing files to disk.
-func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Values, releaseName, outputDir string, subNotes, useReleaseName, includeCrds bool, pr postrender.PostRenderer, dryRun bool) ([]*release.Hook, *bytes.Buffer, string, error) {
+//
+//	This code has to do with writing files to disk.
+func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Values, releaseName, outputDir string, subNotes, useReleaseName, includeCrds bool, pr postrender.PostRenderer, dryRun bool) ([]*release.Hook, *bytes.Buffer, string, []engine.Warning, error) {
 	hs := []*release.Hook{}
 	b := bytes.NewBuffer(nil)
 
 	caps, err := cfg.getCapabilities()
 	if err != nil {
-		return hs, b, "", err
+		return hs, b, "", nil, err
 	}
 
 	if ch.Metadata.KubeVersion != "" {
 		if !chartutil.IsCompatibleRange(ch.Metadata.KubeVersion, caps.KubeVersion.String()) {
-			return hs, b, "", errors.Errorf("chart requires kubeVersion: %s which is incompatible with Kubernetes %s", ch.Metadata.KubeVersion, caps.KubeVersion.String())
+			return hs, b, "", nil, errors.Errorf("chart requires kubeVersion: %s which is incompatible with Kubernetes %s", ch.Metadata.KubeVersion, caps.KubeVersion.String())
 		}
 	}
 
@@ -125,18 +126,20 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 	// is mocked. It is not up to the template author to decide when the user wants to
 	// connect to the cluster. So when the user says to dry run, respect the user's
 	// wishes and do not connect to the cluster.
+	var theEngine engine.Engine
 	if !dryRun && cfg.RESTClientGetter != nil {
 		restConfig, err := cfg.RESTClientGetter.ToRESTConfig()
 		if err != nil {
-			return hs, b, "", err
+			return hs, b, "", nil, err
 		}
-		files, err2 = engine.RenderWithClient(ch, values, restConfig)
+		theEngine = engine.NewEngineWithClient(restConfig)
 	} else {
-		files, err2 = engine.Render(ch, values)
+		theEngine = engine.NewEngine()
 	}
+	files, err2 = theEngine.Render(ch, values)
 
 	if err2 != nil {
-		return hs, b, "", err2
+		return hs, b, "", nil, err2
 	}
 
 	// NOTES.txt gets rendered like all the other files, but because it's not a hook nor a resource,
@@ -175,7 +178,7 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 			}
 			fmt.Fprintf(b, "---\n# Source: %s\n%s\n", name, content)
 		}
-		return hs, b, "", err
+		return hs, b, "", nil, err
 	}
 
 	// Aggregate all valid manifests into one big doc.
@@ -188,7 +191,7 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 			} else {
 				err = writeToFile(outputDir, crd.Filename, string(crd.File.Data[:]), fileWritten[crd.Name])
 				if err != nil {
-					return hs, b, "", err
+					return hs, b, "", nil, err
 				}
 				fileWritten[crd.Name] = true
 			}
@@ -209,7 +212,7 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 			// used by install or upgrade
 			err = writeToFile(newDir, m.Name, m.Content, fileWritten[m.Name])
 			if err != nil {
-				return hs, b, "", err
+				return hs, b, "", nil, err
 			}
 			fileWritten[m.Name] = true
 		}
@@ -218,11 +221,11 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 	if pr != nil {
 		b, err = pr.Run(b)
 		if err != nil {
-			return hs, b, notes, errors.Wrap(err, "error while running post render on files")
+			return hs, b, notes, nil, errors.Wrap(err, "error while running post render on files")
 		}
 	}
 
-	return hs, b, notes, nil
+	return hs, b, notes, theEngine.GetWarnings(), nil
 }
 
 // RESTClientGetter gets the rest client

pkg/action/install.go

@@ -256,7 +256,7 @@ func (i *Install) RunWithContext(ctx context.Context, chrt *chart.Chart, vals ma
 	rel := i.createRelease(chrt, vals)
 
 	var manifestDoc *bytes.Buffer
-	rel.Hooks, manifestDoc, rel.Info.Notes, err = i.cfg.renderResources(chrt, valuesToRender, i.ReleaseName, i.OutputDir, i.SubNotes, i.UseReleaseName, i.IncludeCRDs, i.PostRenderer, i.DryRun)
+	rel.Hooks, manifestDoc, rel.Info.Notes, rel.Warnings, err = i.cfg.renderResources(chrt, valuesToRender, i.ReleaseName, i.OutputDir, i.SubNotes, i.UseReleaseName, i.IncludeCRDs, i.PostRenderer, i.DryRun)
 	// Even for errors, attach this if available
 	if manifestDoc != nil {
 		rel.Manifest = manifestDoc.String()

pkg/action/upgrade.go

@@ -231,7 +231,7 @@ func (u *Upgrade) prepareUpgrade(name string, chart *chart.Chart, vals map[strin
 		return nil, nil, err
 	}
 
-	hooks, manifestDoc, notesTxt, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, u.DryRun)
+	hooks, manifestDoc, notesTxt, warnings, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, u.DryRun)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -250,6 +250,7 @@ func (u *Upgrade) prepareUpgrade(name string, chart *chart.Chart, vals map[strin
 		},
 		Version:  revision,
 		Manifest: manifestDoc.String(),
+		Warnings: warnings,
 		Hooks:    hooks,
 	}
 

pkg/engine/engine.go

@@ -42,6 +42,21 @@ type Engine struct {
 	LintMode bool
 	// the rest config to connect to the kubernetes api
 	config *rest.Config
+
+	warnings *Warnings
+}
+
+type Warning struct {
+	Message string
+}
+
+type Warnings []Warning
+
+func (w *Warnings) append(warning Warning) {
+	if w == nil {
+		w = &Warnings{}
+	}
+	*w = append(*w, warning)
 }
 
 // Render takes a chart, optional values, and value overrides, and attempts to render the Go templates.
@@ -71,16 +86,26 @@ func (e Engine) Render(chrt *chart.Chart, values chartutil.Values) (map[string]s
 // Render takes a chart, optional values, and value overrides, and attempts to
 // render the Go templates using the default options.
 func Render(chrt *chart.Chart, values chartutil.Values) (map[string]string, error) {
-	return new(Engine).Render(chrt, values)
+	return NewEngine().Render(chrt, values)
 }
 
 // RenderWithClient takes a chart, optional values, and value overrides, and attempts to
 // render the Go templates using the default options. This engine is client aware and so can have template
 // functions that interact with the client
 func RenderWithClient(chrt *chart.Chart, values chartutil.Values, config *rest.Config) (map[string]string, error) {
+	return NewEngineWithClient(config).Render(chrt, values)
+}
+
+func NewEngineWithClient(config *rest.Config) Engine {
+	engine := NewEngine()
+	engine.config = config
+	return engine
+}
+
+func NewEngine() Engine {
 	return Engine{
-		config: config,
-	}.Render(chrt, values)
+		warnings: &Warnings{},
+	}
 }
 
 // renderable is an object that can be rendered.
@@ -103,6 +128,13 @@ func warnWrap(warn string) string {
 	return warnStartDelim + warn + warnEndDelim
 }
 
+func (e Engine) GetWarnings() []Warning {
+	if e.warnings == nil {
+		panic("Use NewEngine or NewEngineWithClient to create Engine")
+	}
+	return *e.warnings
+}
+
 // initFunMap creates the Engine's FuncMap and adds context-specific functions.
 func (e Engine) initFunMap(t *template.Template, referenceTpls map[string]renderable) {
 	funcMap := funcMap()
@@ -189,6 +221,17 @@ func (e Engine) initFunMap(t *template.Template, referenceTpls map[string]render
 		funcMap["lookup"] = NewLookupFunction(e.config)
 	}
 
+	funcMap["warn"] = func(msg string) string {
+		if e.warnings == nil { // Fallback if Engine was not created with constructor
+			fmt.Println("Warning:", msg)
+		} else {
+			e.warnings.append(Warning{
+				Message: msg,
+			})
+		}
+		return ""
+	}
+
 	t.Funcs(funcMap)
 }
 

pkg/release/release.go

@@ -15,7 +15,10 @@ limitations under the License.
 
 package release
 
-import "helm.sh/helm/v3/pkg/chart"
+import (
+	"helm.sh/helm/v3/pkg/chart"
+	"helm.sh/helm/v3/pkg/engine"
+)
 
 // Release describes a deployment of a chart, together with the chart
 // and the variables used to deploy that chart.
@@ -37,6 +40,8 @@ type Release struct {
 	Version int `json:"version,omitempty"`
 	// Namespace is the kubernetes namespace of the release.
 	Namespace string `json:"namespace,omitempty"`
+
+	Warnings []engine.Warning
 	// Labels of the release.
 	// Disabled encoding into Json cause labels are stored in storage driver metadata field.
 	Labels map[string]string `json:"-"`