Add "did you mean?" suggestions for variable reference typos

acceptance/bundle/variables/did-you-mean/databricks.yml

@@ -0,0 +1,11 @@
+bundle:
+  name: did-you-mean
+
+variables:
+  my_cluster_id:
+    default: "abc-123"
+
+resources:
+  jobs:
+    my_job:
+      name: "test-${var.my_clster_id}"

acceptance/bundle/variables/did-you-mean/output.txt

@@ -0,0 +1,11 @@
+Error: reference does not exist: ${var.my_clster_id}. Did you mean ${var.my_cluster_id}?
+
+Name: did-you-mean
+Target: default
+Workspace:
+  User: [USERNAME]
+  Path: /Workspace/Users/[USERNAME]/.bundle/did-you-mean/default
+
+Found 1 error
+
+Exit code: 1

acceptance/bundle/variables/did-you-mean/script

@@ -0,0 +1 @@
+$CLI bundle validate

bundle/config/mutator/resolve_variable_references.go

@@ -43,7 +43,8 @@
 	"variables",
 }
 
 var artifactPath = dyn.MustPathFromString("artifacts")
+var resourcesPath = dyn.MustPathFromString("resources")
 
 type resolveVariableReferences struct {
 	prefixes    []string
@@ -202,6 +203,8 @@
 		//
 		normalized, _ := convert.Normalize(b.Config, root, convert.IncludeMissingFields)
 
+		suggestFn := m.makeSuggestFn(normalized, prefixes, varPath)
+
 		// If the pattern is nil, we resolve references in the entire configuration.
 		root, err := dyn.MapByPattern(root, m.pattern, func(p dyn.Path, v dyn.Value) (dyn.Value, error) {
 			// Resolve variable references in all values.
@@ -235,8 +238,50 @@
 					}
 				}
 
+				// For references starting with "resources" that are not in
+				// the resolution prefixes: validate the path against the
+				// normalized tree. If invalid, emit a warning with a
+				// suggestion. Either way, skip resolution (resources are
+				// resolved later by terraform).
+				if path.HasPrefix(resourcesPath) {
+					_, lookupErr := m.lookupFn(normalized, path, b)
+					if lookupErr != nil && dyn.IsNoSuchKeyError(lookupErr) {
+						key := rewriteToVarShorthand(path.String())
+						msg := fmt.Sprintf("reference does not exist: ${%s}", key)
+						if suggestion := suggestFn(key); suggestion != "" {
+							msg += fmt.Sprintf(". Did you mean ${%s}?", suggestion)
+						}
+						diags = diags.Append(diag.Diagnostic{
+							Severity: diag.Warning,
+							Summary:  msg,
+						})
+					}
+					return dyn.InvalidValue, dynvar.ErrSkipResolution
+				}
+
+				// Check for prefix typos before skipping. If the first
+				// component is close to a valid prefix, emit a warning
+				// with a suggestion. The reference is left unresolved to
+				// avoid breaking existing behavior.
+				if len(path) > 0 {
+					firstKey := path[0].Key()
+					prefixNames := m.suggestPrefixNames(prefixes)
+					best, dist := closestMatch(firstKey, prefixNames)
+					if best != "" && dist > 0 {
+						corrected := make(dyn.Path, len(path))
+						copy(corrected, path)
+						corrected[0] = dyn.Key(best)
+						suggestion := rewriteToVarShorthand(corrected.String())
+						key := rewriteToVarShorthand(path.String())
+						diags = diags.Append(diag.Diagnostic{
+							Severity: diag.Warning,
+							Summary:  fmt.Sprintf("reference does not exist: ${%s}. Did you mean ${%s}?", key, suggestion),
+						})
+					}
+				}
+
 				return dyn.InvalidValue, dynvar.ErrSkipResolution
-			})
+			}, dynvar.WithSuggestFn(suggestFn))
 		})
 		if err != nil {
 			return dyn.InvalidValue, err