add confmap.Converter an option for ocb build manifest/template (#11584)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Adds ability to add confmap.Converter as a module to build/import with
ocb

<!-- Issue number if applicable -->
#### Link to tracking issue
Fixes
#11582

<!--Describe what testing was performed and which tests were added.-->
#### Testing
Added validation tests for pulling the converter go module in
cmd/builder template/build process.
Additionally, I took the default otelcorecol manifest, added a
`converters` section, and added the `expandconverter` and verified that
a custom collector both built, started up, and exited successfully.

<!--Describe the documentation added.-->
#### Documentation
Changelog file added. I can also update the documentation in cmd/builder
README if community thinks that is necessary. Since `confmap.Converter`
is not yet registered in the OTel registry and does not have any
existing components published save for the deprecated `expandconverter`
I was not certain if anything further than a changelog was necessary.
<!--Please delete paragraphs that you did not use before submitting.-->

---------

Co-authored-by: Andrzej Stencel <[email protected]>

.chloggen/builder-confmap-converters.yaml

@@ -0,0 +1,36 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: cmd/builder
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Allow configuring `confmap.Converter` components in ocb.
+
+# One or more tracking issues or pull requests related to the change
+issues: [11582]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  If no converters are specified, there will be no converters added.
+  Currently, the only published converter is `expandconverter` which is 
+  deprecated as of v0.107.0, but can still be added for testing purposes.
+
+  To configure a custom converter, make sure your converter implements the converter
+  interface and is published as a go module (or replaced locally if not published).
+  You may then use the `converters` key in your OCB build manifest with a list of
+  Go modules (and replaces as necessary) to include your converter.
+
+  Please note that converters are order-dependent. The confmap will apply converters
+  in order of which they are listed in your manifest if there is more than one.
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

cmd/builder/internal/builder/config.go

@@ -43,6 +43,7 @@ type Config struct {
 	Processors   []Module     `mapstructure:"processors"`
 	Connectors   []Module     `mapstructure:"connectors"`
 	Providers    []Module     `mapstructure:"providers"`
+	Converters   []Module     `mapstructure:"converters"`
 	Replaces     []string     `mapstructure:"replaces"`
 	Excludes     []string     `mapstructure:"excludes"`
 
@@ -142,6 +143,7 @@ func (c *Config) Validate() error {
 		validateModules("processor", c.Processors),
 		validateModules("connector", c.Connectors),
 		validateModules("provider", c.Providers),
+		validateModules("converter", c.Converters),
 	)
 }
 
@@ -194,7 +196,10 @@ func (c *Config) ParseModules() error {
 	if err != nil {
 		return err
 	}
-
+	c.Converters, err = parseModules(c.Converters)
+	if err != nil {
+		return err
+	}
 	return nil
 }
 
@@ -226,6 +231,10 @@ func parseModules(mods []Module) ([]Module, error) {
 			if err != nil {
 				return mods, fmt.Errorf("module has a relative \"path\" element, but we couldn't resolve the current working dir: %w", err)
 			}
+			// Check if the path exists
+			if _, err := os.Stat(mod.Path); os.IsNotExist(err) {
+				return mods, fmt.Errorf("filepath does not exist: %s", mod.Path)
+			}
 		}
 
 		parsedModules = append(parsedModules, mod)

cmd/builder/internal/builder/config_test.go

@@ -36,12 +36,27 @@ func TestParseModules(t *testing.T) {
 	assert.Equal(t, "repo", cfg.Extensions[0].Name)
 }
 
+func TestInvalidConverter(t *testing.T) {
+	// Create a Config instance with invalid Converters
+	config := &Config{
+		Converters: []Module{
+			{
+				Path: "./invalid/module/path", // Invalid module path to trigger an error
+			},
+		},
+	}
+
+	// Call the method and expect an error
+	err := config.ParseModules()
+	require.Error(t, err, "expected an error when parsing invalid modules")
+}
+
 func TestRelativePath(t *testing.T) {
 	// prepare
 	cfg := Config{
 		Extensions: []Module{{
 			GoMod: "some-module",
-			Path:  "./some-module",
+			Path:  "./templates",
 		}},
 	}
 
@@ -116,7 +131,7 @@ func TestMissingModule(t *testing.T) {
 			cfg: Config{
 				Logger: zap.NewNop(),
 				Exporters: []Module{{
-					Import: "invali",
+					Import: "invalid",
 				}},
 			},
 			err: errMissingGoMod,
@@ -139,6 +154,15 @@ func TestMissingModule(t *testing.T) {
 			},
 			err: errMissingGoMod,
 		},
+		{
+			cfg: Config{
+				Logger: zap.NewNop(),
+				Converters: []Module{{
+					Import: "invalid",
+				}},
+			},
+			err: errMissingGoMod,
+		},
 	}
 
 	for _, test := range configurations {
@@ -235,6 +259,7 @@ func TestSkipsNilFieldValidation(t *testing.T) {
 	cfg, err := NewDefaultConfig()
 	require.NoError(t, err)
 	cfg.Providers = nil
+	cfg.Converters = nil
 	assert.NoError(t, cfg.Validate())
 }
 

cmd/builder/internal/builder/main.go

@@ -213,7 +213,7 @@ func processAndWrite(cfg *Config, tmpl *template.Template, outFile string, tmplP
 }
 
 func (c *Config) allComponents() []Module {
-	return slices.Concat[[]Module](c.Exporters, c.Receivers, c.Processors, c.Extensions, c.Connectors, c.Providers)
+	return slices.Concat[[]Module](c.Exporters, c.Receivers, c.Processors, c.Extensions, c.Connectors, c.Providers, c.Converters)
 }
 
 func (c *Config) readGoModFile() (string, map[string]string, error) {

cmd/builder/internal/builder/templates/go.mod.tmpl

@@ -8,6 +8,9 @@ require (
 	{{- range .Providers}}
 	{{if .GoMod}}{{.GoMod}}{{end}}
 	{{- end}}
+	{{- range .Converters}}
+	{{if .GoMod}}{{.GoMod}}{{end}}
+	{{- end}}
 	{{- range .Connectors}}
 	{{if .GoMod}}{{.GoMod}}{{end}}
 	{{- end}}

cmd/builder/internal/builder/templates/main.go.tmpl

@@ -8,6 +8,9 @@ import (
 
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/confmap"
+	{{- range .Converters}}
+	{{.Name}} "{{.Import}}"
+	{{- end}}	
 	{{- range .Providers}}
 	{{.Name}} "{{.Import}}"
 	{{- end}}
@@ -31,6 +34,13 @@ func main() {
 					{{.Name}}.NewFactory(),
 					{{- end}}
 				},
+				{{- if .Converters }}
+				ConverterFactories: []confmap.ConverterFactory{
+					{{- range .Converters}}
+					{{.Name}}.NewFactory(),
+					{{- end}}
+				},
+				{{- end }}
 				{{- if .ConfResolver.DefaultURIScheme }}
 				DefaultScheme: "{{ .ConfResolver.DefaultURIScheme }}",
 				{{- end }}