[cmd/builder] Fix otelcol_version being ignored (open-telemetry#8713)

Adds `go.opentelemetry.io/collector/otelcol` to `go.mod` template for
the builder. This fixes open-telemetry#8692.

Since open-telemetry#8443, the `otelcol` folder is its own component. Before this
change, `otelcol_version` was enforced by the `collector` module
dependency:

https://github.com/open-telemetry/opentelemetry-collector/blob/287b98f6973fd6baa278150b9fca8c83abea0af4/cmd/builder/internal/builder/templates/go.mod.tmpl#L23

After this change, the `go mod tidy` step here:

https://github.com/open-telemetry/opentelemetry-collector/blob/287b98f6973fd6baa278150b9fca8c83abea0af4/cmd/builder/internal/builder/main.go#L115

will add the latest available version for the `otelcol` module since
none of the components actually depend on it. For example, with the
`v0.86.0` builder config the output is as follows:

```
❯ go mod tidy -v -compat=1.20
go: finding module for package go.opentelemetry.io/collector/otelcol
go: found go.opentelemetry.io/collector/otelcol in go.opentelemetry.io/collector/otelcol v0.87.0
```

Explicitly adding `otelcol` makes it so the `otelcol_version` is
correctly honored.

**Link to tracking Issue:** Fixes open-telemetry#8692

.chloggen/mx-psi_fix-builder.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# 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: "Fix ocb ignoring `otelcol_version` when set to v0.86.0 or later"
+
+# One or more tracking issues or pull requests related to the change
+issues: [8692]
+
+# (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:
+
+# 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: []

cmd/builder/go.mod

@@ -6,6 +6,7 @@ module go.opentelemetry.io/collector/cmd/builder
 go 1.20
 
 require (
+	github.com/hashicorp/go-version v1.6.0
 	github.com/knadh/koanf/parsers/yaml v0.1.0
 	github.com/knadh/koanf/providers/env v0.1.0
 	github.com/knadh/koanf/providers/file v0.1.0

cmd/builder/go.sum

@@ -4,6 +4,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/fsnotify/fsnotify v1.6.0 h1:n+5WquG0fcWoWp6xPWfHdbskMCQaFnG6PfBrh1Ky4HY=
 github.com/fsnotify/fsnotify v1.6.0/go.mod h1:sl3t1tCWJFWoRz9R8WJCbQihKKwmorjAbSClcnxKAGw=
+github.com/hashicorp/go-version v1.6.0 h1:feTTfFNnjP967rlCxM/I9g701jU+RN74YKx2mOkIeek=
+github.com/hashicorp/go-version v1.6.0/go.mod h1:fltr4n8CU8Ke44wwGCBoEymUuxUHl09ZGVZPK5anwXA=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/knadh/koanf/maps v0.1.1 h1:G5TjmUh2D7G2YWf5SQQqSiHRJEjaicvU0KpypqB3NIs=

cmd/builder/internal/builder/config.go

@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/hashicorp/go-version"
 	"go.uber.org/multierr"
 	"go.uber.org/zap"
 )
@@ -40,15 +41,16 @@ type Config struct {
 
 // Distribution holds the parameters for the final binary
 type Distribution struct {
-	Module           string `mapstructure:"module"`
-	Name             string `mapstructure:"name"`
-	Go               string `mapstructure:"go"`
-	Description      string `mapstructure:"description"`
-	OtelColVersion   string `mapstructure:"otelcol_version"`
-	OutputPath       string `mapstructure:"output_path"`
-	Version          string `mapstructure:"version"`
-	BuildTags        string `mapstructure:"build_tags"`
-	DebugCompilation bool   `mapstructure:"debug_compilation"`
+	Module               string `mapstructure:"module"`
+	Name                 string `mapstructure:"name"`
+	Go                   string `mapstructure:"go"`
+	Description          string `mapstructure:"description"`
+	OtelColVersion       string `mapstructure:"otelcol_version"`
+	RequireOtelColModule bool   `mapstructure:"-"` // required for backwards-compatibility with builds older than 0.86.0
+	OutputPath           string `mapstructure:"output_path"`
+	Version              string `mapstructure:"version"`
+	BuildTags            string `mapstructure:"build_tags"`
+	DebugCompilation     bool   `mapstructure:"debug_compilation"`
 }
 
 // Module represents a receiver, exporter, processor or extension for the distribution
@@ -108,6 +110,21 @@ func (c *Config) SetGoPath() error {
 	return nil
 }
 
+func (c *Config) SetRequireOtelColModule() error {
+	constraint, err := version.NewConstraint(">= 0.86.0")
+	if err != nil {
+		return err
+	}
+
+	otelColVersion, err := version.NewVersion(c.Distribution.OtelColVersion)
+	if err != nil {
+		return err
+	}
+
+	c.Distribution.RequireOtelColModule = constraint.Check(otelColVersion)
+	return nil
+}
+
 // ParseModules will parse the Modules entries and populate the missing values
 func (c *Config) ParseModules() error {
 	var err error

cmd/builder/internal/builder/config_test.go

@@ -192,3 +192,36 @@ func TestDebugOptionSetConfig(t *testing.T) {
 	assert.NoError(t, cfg.Validate())
 	assert.True(t, cfg.Distribution.DebugCompilation)
 }
+
+func TestRequireOtelColModule(t *testing.T) {
+	tests := []struct {
+		Version                      string
+		ExpectedRequireOtelColModule bool
+	}{
+		{
+			Version:                      "0.85.0",
+			ExpectedRequireOtelColModule: false,
+		},
+		{
+			Version:                      "0.86.0",
+			ExpectedRequireOtelColModule: true,
+		},
+		{
+			Version:                      "0.86.1",
+			ExpectedRequireOtelColModule: true,
+		},
+		{
+			Version:                      "1.0.0",
+			ExpectedRequireOtelColModule: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.Version, func(t *testing.T) {
+			cfg := NewDefaultConfig()
+			cfg.Distribution.OtelColVersion = tt.Version
+			require.NoError(t, cfg.SetRequireOtelColModule())
+			assert.Equal(t, tt.ExpectedRequireOtelColModule, cfg.Distribution.RequireOtelColModule)
+		})
+	}
+}

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

@@ -20,7 +20,7 @@ require (
 	{{- range .Processors}}
 	{{if .GoMod}}{{.GoMod}}{{end}}
 	{{- end}}
-	go.opentelemetry.io/collector v{{.Distribution.OtelColVersion}}
+	go.opentelemetry.io/collector{{if .Distribution.RequireOtelColModule}}/otelcol{{end}} v{{.Distribution.OtelColVersion}}
 )
 
 require (

cmd/builder/internal/command.go

@@ -64,6 +64,10 @@ configuration is provided, ocb will generate a default Collector.
 				return fmt.Errorf("go not found: %w", err)
 			}
 
+			if err := cfg.SetRequireOtelColModule(); err != nil {
+				return fmt.Errorf("unable to compare otelcol version: %w", err)
+			}
+
 			if err := cfg.ParseModules(); err != nil {
 				return fmt.Errorf("invalid module configuration: %w", err)
 			}

cmd/otelcorecol/go.mod

@@ -17,7 +17,7 @@ require (
 	go.opentelemetry.io/collector/extension v0.87.0
 	go.opentelemetry.io/collector/extension/ballastextension v0.87.0
 	go.opentelemetry.io/collector/extension/zpagesextension v0.87.0
-	go.opentelemetry.io/collector/otelcol v0.0.0-00010101000000-000000000000
+	go.opentelemetry.io/collector/otelcol v0.87.0
 	go.opentelemetry.io/collector/processor v0.87.0
 	go.opentelemetry.io/collector/processor/batchprocessor v0.87.0
 	go.opentelemetry.io/collector/processor/memorylimiterprocessor v0.87.0