pkg/components/util: use Helm post-renderer instead of Manifests field

As Manifests filed in Chart object is a custom field, added to our fork
of Helm. Now Helm offers post-renderer feature, which allows to further
customize the manfiests after Helm's templating engine and before the
installation of the manifests.

This allows us to use post-renderer feature and drop one of maintained
custom patches, which means less maintenance for us.

Signed-off-by: Mateusz Gozdek <mateusz@kinvolk.io>

pkg/components/util/helm.go

@@ -214,11 +214,7 @@ func chartFromManifests(metadata components.Metadata, manifests map[string]strin
 			Name: p,
 		}
 
-		// Apply rendered manifests to Manifests slice, which does not run through the rendering engine
-		// again when the chart is being installed. This is required, as some charts use complex escaping
-		// syntax, which breaks if the templates are evaluated twice. This, for example, breaks
-		// the prometheus-operator chart.
-		ch.Manifests = append(ch.Manifests, f)
+		ch.Templates = append(ch.Templates, f)
 	}
 
 	// If we collected any CRDs, put them in the special file in the dedicated crds/ directory.

pkg/components/util/helm_test.go

@@ -106,11 +106,11 @@ metadata:
 		t.Fatalf("Chart should be created, got: %v", err)
 	}
 
-	if len(chart.Manifests) != 1 { //nolint:gomnd
+	if len(chart.Templates) != 1 {
 		t.Fatalf("Manifest file with the namespace should still be added, as it may contain other objects")
 	}
 
-	if len(chart.Manifests[0].Data) != 0 {
+	if len(chart.Templates[0].Data) != 0 {
 		t.Fatalf("Namespace object should be removed from chart")
 	}
 }
@@ -140,7 +140,11 @@ metadata:
 		t.Fatalf("Chart should be created, got: %v", err)
 	}
 
-	if len(chart.Manifests[0].Data) == 0 {
+	if len(chart.Templates) != 1 {
+		t.Fatalf("templates should include exactly one object")
+	}
+
+	if len(chart.Templates[0].Data) == 0 {
 		t.Fatalf("Other objects should be retained in the file containing Namespace object")
 	}
 }
@@ -165,7 +169,7 @@ metadata:
 		t.Fatalf("Chart should be created, got: %v", err)
 	}
 
-	if len(chart.Manifests[0].Data) == 0 {
+	if len(chart.Templates[0].Data) == 0 {
 		t.Fatalf("Only Namespace object with matching namespace name should be filtered")
 	}
 }
@@ -188,15 +192,15 @@ metadata:
 		t.Fatalf("Chart should be created, got: %v", err)
 	}
 
-	if len(chart.Manifests) != 1 { //nolint:gomnd
+	if len(chart.Templates) != 1 {
 		t.Fatalf("Manifest file with the CRDs should still be added, as it may contain other objects")
 	}
 
-	if len(chart.Manifests[0].Data) != 0 {
+	if len(chart.Templates[0].Data) != 0 {
 		t.Fatalf("CRD object should be removed from the manifests file")
 	}
 
-	if len(chart.Files) != 1 { //nolint:gomnd
+	if len(chart.Files) != 1 {
 		t.Fatalf("CRD object should be added to Files field")
 	}
 

pkg/components/util/install.go

@@ -15,6 +15,7 @@
 package util
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 
@@ -104,10 +105,45 @@ type helmAction struct {
 	wait         bool
 }
 
+// postRender is a Lokomotive post-renderer for Helm, which allows bypassing Helm templating engine
+// by copying manifests from Templates field and then including them into the chart.
+//
+// As we render original charts twice (once when we render manifests ourselves to be able to print them
+// to the user and then again via Helm, when it installs/upgrades/uninstalls the release.
+//
+// This is required as some charts use complex escaping syntax, which breaks if the templates
+// are evaluated twice. This, for example, breaks the prometheus-operator chart.
+type postRender struct {
+	manifests bytes.Buffer
+}
+
+// Run implements postrender.PostRenderer interface by ignoring given templates from Helm and returning
+// manifests defined at creation time.
+func (pr postRender) Run(renderedManifests *bytes.Buffer) (modifiedManifests *bytes.Buffer, err error) {
+	return &pr.manifests, nil
+}
+
+// chartTemplatesToPostRender creates PostRenderer from given chart templates and resets
+// chart's Templates field so it does not run twice trough rendering engine.
+func chartTemplatesToPostRender(c *chart.Chart) postRender {
+	var buf bytes.Buffer
+
+	for _, template := range c.Templates {
+		fmt.Fprintf(&buf, "\n---\n# %s\n%s", template.Name, template.Data)
+	}
+
+	c.Templates = nil
+
+	return postRender{
+		manifests: buf,
+	}
+}
+
 func install(helmAction *helmAction, namespace string) error {
 	install := action.NewInstall(helmAction.actionConfig)
 	install.ReleaseName = helmAction.releaseName
 	install.Namespace = namespace
+	install.PostRenderer = chartTemplatesToPostRender(helmAction.chart)
 
 	// Currently, we install components one-by-one, in the order how they are
 	// defined in the configuration and we do not support any dependencies between
@@ -133,6 +169,7 @@ func upgrade(helmAction *helmAction) error {
 	upgrade := action.NewUpgrade(helmAction.actionConfig)
 	upgrade.Wait = helmAction.wait
 	upgrade.RecreateResources = true
+	upgrade.PostRenderer = chartTemplatesToPostRender(helmAction.chart)
 
 	if _, err := upgrade.Run(helmAction.releaseName, helmAction.chart, map[string]interface{}{}); err != nil {
 		return fmt.Errorf("upgrading release failed: %w", err)