[mdatagen] Only include context import when needed (#10884)

#### Description

Updates the generated_telemetry and generated_metrics files to only
include the context import when there are async metrics.

#### Link to tracking issue

- Closes #10883

#### Testing

Added unit test to verify expected behaviour.

.chloggen/mdatagen-context.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: mdatagen
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Update generated telemetry template to only include context import when there are async metrics.
+
+# One or more tracking issues or pull requests related to the change
+issues: [10883]
+
+# (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/mdatagen/main_test.go

@@ -21,6 +21,7 @@ func TestRunContents(t *testing.T) {
 	tests := []struct {
 		yml                    string
 		wantMetricsGenerated   bool
+		wantMetricsContext     bool
 		wantConfigGenerated    bool
 		wantTelemetryGenerated bool
 		wantStatusGenerated    bool
@@ -98,6 +99,12 @@ func TestRunContents(t *testing.T) {
 			yml:     "invalid_telemetry_missing_value_type_for_histogram.yaml",
 			wantErr: true,
 		},
+		{
+			yml:                  "async_metric.yaml",
+			wantMetricsGenerated: true,
+			wantConfigGenerated:  true,
+			wantStatusGenerated:  true,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.yml, func(t *testing.T) {
@@ -120,10 +127,18 @@ foo
 			}
 			require.NoError(t, err)
 
+			var contents []byte
 			if tt.wantMetricsGenerated {
 				require.FileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_metrics.go"))
 				require.FileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_metrics_test.go"))
 				require.FileExists(t, filepath.Join(tmpdir, "documentation.md"))
+				contents, err = os.ReadFile(filepath.Join(tmpdir, "internal/metadata/generated_metrics.go")) // nolint: gosec
+				require.NoError(t, err)
+				if tt.wantMetricsContext {
+					require.Contains(t, string(contents), "\"context\"")
+				} else {
+					require.NotContains(t, string(contents), "\"context\"")
+				}
 			} else {
 				require.NoFileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_metrics.go"))
 				require.NoFileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_metrics_test.go"))
@@ -141,6 +156,13 @@ foo
 				require.FileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_telemetry.go"))
 				require.FileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_telemetry_test.go"))
 				require.FileExists(t, filepath.Join(tmpdir, "documentation.md"))
+				contents, err = os.ReadFile(filepath.Join(tmpdir, "internal/metadata/generated_telemetry.go")) // nolint: gosec
+				require.NoError(t, err)
+				if tt.wantMetricsContext {
+					require.Contains(t, string(contents), "\"context\"")
+				} else {
+					require.NotContains(t, string(contents), "\"context\"")
+				}
 			} else {
 				require.NoFileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_telemetry.go"))
 				require.NoFileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_telemetry_test.go"))
@@ -150,7 +172,6 @@ foo
 				require.NoFileExists(t, filepath.Join(tmpdir, "documentation.md"))
 			}
 
-			var contents []byte
 			if tt.wantStatusGenerated {
 				require.FileExists(t, filepath.Join(tmpdir, "internal/metadata/generated_status.go"))
 				contents, err = os.ReadFile(filepath.Join(tmpdir, "README.md")) // nolint: gosec

cmd/mdatagen/templates/telemetry.go.tmpl

@@ -4,7 +4,12 @@ package {{ .Package }}
 
 import (
     {{- if .Telemetry.Metrics }}
+    {{- range $_, $metric := .Telemetry.Metrics }}
+    {{- if $metric.Data.Async }}
     "context"
+    {{- break}}
+    {{- end }}
+    {{- end }}
     "errors"
     {{- end }}
 

cmd/mdatagen/testdata/async_metric.yaml

@@ -0,0 +1,24 @@
+type: metricreceiver
+
+status:
+  class: receiver
+  stability:
+    development: [logs]
+    beta: [traces]
+    stable: [metrics]
+  distributions: [contrib]
+  warnings:
+    - Any additional information that should be brought to the consumer's attention
+
+metrics:
+  metric:
+    enabled: true
+    description: Description.
+    unit: s
+    gauge:
+      value_type: double
+      async: true
+
+tests:
+  skip_lifecycle: true
+  skip_shutdown: true