metric: Track if artifacts variable references are used (#3368)

## Changes
Track if the artifacts variable references are used

## Why
This can be a useful insight to see if such variables are used at all,
and if not, we might move to resolving such variables altogether.
Prompted by
#3364 (comment)

## Tests
Added an acceptance test

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Author: andrewnester

acceptance/bundle/telemetry/deploy-artifacts-variables/databricks.yml

@@ -0,0 +1,23 @@
+bundle:
+  name: deploy-artifacts-variables
+
+artifacts:
+  test_artifact:
+    type: whl
+    path: .
+    build: "echo 'Building...'"
+    files:
+      - source: ./databricks.yml
+
+resources:
+  jobs:
+    test-job:
+      name: test-job
+
+targets:
+  dev: {}
+  prod:
+    resources:
+      jobs:
+        test-job:
+          name: "test-job that does ${artifacts.test_artifact.build}"

acceptance/bundle/telemetry/deploy-artifacts-variables/out.test.toml

@@ -0,0 +1,5 @@
+Local = true
+Cloud = false
+
+[EnvMatrix]
+  DATABRICKS_CLI_DEPLOYMENT = ["terraform", "direct-exp"]

acceptance/bundle/telemetry/deploy-artifacts-variables/output.txt

@@ -0,0 +1,26 @@
+
+>>> [CLI] bundle deploy -t dev
+Building test_artifact...
+Uploading databricks.yml...
+Uploading bundle files to /Workspace/Users/[USERNAME]/.bundle/deploy-artifacts-variables/dev/files...
+Deploying resources...
+Updating deployment state...
+Deployment complete!
+
+=== No artifact metrics expected
+>>> cat out.requests.txt
+
+>>> [CLI] bundle deploy -t prod
+Building test_artifact...
+Uploading databricks.yml...
+Uploading bundle files to /Workspace/Users/[USERNAME]/.bundle/deploy-artifacts-variables/prod/files...
+Deploying resources...
+Updating deployment state...
+Deployment complete!
+
+=== Artifact metrics expected
+>>> cat out.requests.txt
+{
+  "key": "artifacts_reference_used",
+  "value": true
+}

acceptance/bundle/telemetry/deploy-artifacts-variables/script

@@ -0,0 +1,11 @@
+trace $CLI bundle deploy -t dev
+
+title "No artifact metrics expected"
+trace cat out.requests.txt | jq 'select(has("path") and .path == "/telemetry-ext") | .body.protoLogs[] | fromjson | .entry.databricks_cli_log.bundle_deploy_event.experimental.bool_values[] | select(.key == "artifacts_reference_used")'
+
+trace $CLI bundle deploy -t prod
+
+title "Artifact metrics expected"
+trace cat out.requests.txt | jq 'select(has("path") and .path == "/telemetry-ext") | .body.protoLogs[] | fromjson | .entry.databricks_cli_log.bundle_deploy_event.experimental.bool_values[] | select(.key == "artifacts_reference_used")'
+
+rm out.requests.txt

bundle/bundle.go

@@ -56,6 +56,20 @@ type Metrics struct {
 	ExecutionTimes              []protos.IntMapEntry
 }
 
+// SetBoolValue sets the value of a boolean metric.
+// If the metric does not exist, it is created.
+// If the metric exists, it is updated.
+// Ensures that the metric is unique
+func (m *Metrics) SetBoolValue(key string, value bool) {
+	for i, v := range m.BoolValues {
+		if v.Key == key {
+			m.BoolValues[i].Value = value
+			return
+		}
+	}
+	m.BoolValues = append(m.BoolValues, protos.BoolMapEntry{Key: key, Value: value})
+}
+
 func (m *Metrics) AddBoolValue(key string, value bool) {
 	m.BoolValues = append(m.BoolValues, protos.BoolMapEntry{Key: key, Value: value})
 }

bundle/config/mutator/resolve_variable_references.go

@@ -43,6 +43,8 @@ var defaultPrefixes = []string{
 	"variables",
 }
 
+var artifactPath = dyn.MustPathFromString("artifacts")
+
 type resolveVariableReferences struct {
 	prefixes    []string
 	pattern     dyn.Pattern
@@ -54,6 +56,8 @@ type resolveVariableReferences struct {
 	// includeResources can be used with appropriate pattern to avoid resolving variables
 	// outside of 'resources'.
 	includeResources bool
+
+	artifactsReferenceUsed bool
 }
 
 func ResolveVariableReferencesOnlyResources(prefixes ...string) bundle.Mutator {
@@ -171,6 +175,11 @@ func (m *resolveVariableReferences) Apply(ctx context.Context, b *bundle.Bundle)
 			break
 		}
 	}
+
+	if m.artifactsReferenceUsed {
+		b.Metrics.SetBoolValue("artifacts_reference_used", true)
+	}
+
 	return diags
 }
 
@@ -212,6 +221,11 @@ func (m *resolveVariableReferences) resolveOnce(b *bundle.Bundle, prefixes []dyn
 					path = newPath
 				}
 
+				// If the path starts with "artifacts", we need to add a metric to track if this reference is used.
+				if path.HasPrefix(artifactPath) {
+					m.artifactsReferenceUsed = true
+				}
+
 				// Perform resolution only if the path starts with one of the specified prefixes.
 				for _, prefix := range prefixes {
 					if path.HasPrefix(prefix) {