[v0.19.x] internal/plugins: scaffold a vanilla go.kubebuilder.io/v2 project when --project-version=2 (#3697) (#3716)

Author: Eric Stroczynski

changelog/fragments/3-alpha-config.yaml

@@ -0,0 +1,20 @@
+entries:
+  - description: >
+      Changed the `go.operator-sdk.io` plugin to only write a `plugins` PROJECT field and
+      run the OLM integration plugin if the project version is "3-alpha" or above.
+    kind: change
+    breaking: true
+    migration:
+      header: Upgrade your project from version "2" to "3-alpha"
+      body: >
+        The SDK's default Go plugin no longer supports OLM-related project files
+        nor writes a `plugins` PROJECT field for projects scaffolded previously with
+        `operator-sdk init --project-version=2`, Please migrate to project version "3-alpha"
+        for support of these features by adding the following to your `PROJECT` file:
+
+        ```yaml
+        version: "3-alpha" # Updated from "2"
+        layout: go.kubebuilder.io/v2
+        plugins:
+          go.sdk.operatorframework.io/v2-alpha: {}
+        ```

internal/plugins/golang/v2/config.go

@@ -21,7 +21,7 @@ type Config struct{}
 
 // hasPluginConfig returns true if cfg.Plugins contains an exact match for this plugin's key.
 func hasPluginConfig(cfg *config.Config) bool {
-	if len(cfg.Plugins) == 0 {
+	if !cfg.IsV3() || len(cfg.Plugins) == 0 {
 		return false
 	}
 	_, hasKey := cfg.Plugins[pluginConfigKey]

internal/plugins/golang/v2/init.go

@@ -44,16 +44,17 @@ func (p *initPlugin) Run() error {
 		return err
 	}
 
-	// Update the scaffolded Makefile with operator-sdk recipes.
-	// TODO: rewrite this when plugins phase 2 is implemented.
-	if err := initUpdateMakefile("Makefile"); err != nil {
-		return fmt.Errorf("error updating Makefile: %v", err)
-	}
-
-	// Update plugin config section with this plugin's configuration.
-	cfg := Config{}
-	if err := p.config.EncodePluginConfig(pluginConfigKey, cfg); err != nil {
-		return fmt.Errorf("error writing plugin config for %s: %v", pluginConfigKey, err)
+	// Run the Makefile updater and update plugin config section with this plugin's configuration for v3 projects.
+	if p.config.IsV3() {
+		// TODO: rewrite this when plugins phase 2 is implemented.
+		if err := initUpdateMakefile("Makefile"); err != nil {
+			return fmt.Errorf("error updating Makefile: %v", err)
+		}
+
+		cfg := Config{}
+		if err := p.config.EncodePluginConfig(pluginConfigKey, cfg); err != nil {
+			return fmt.Errorf("error writing plugin config for %s: %v", pluginConfigKey, err)
+		}
 	}
 
 	return nil