plugin/convert: Convert cty.PathError to diagnostics with attribute path

plugin/convert/diagnostics.go

@@ -24,6 +24,13 @@ func WarnsAndErrsToProto(warns []string, errs []error) (diags []*proto.Diagnosti
 // This panics if d is not a string or error.
 func AppendProtoDiag(diags []*proto.Diagnostic, d interface{}) []*proto.Diagnostic {
 	switch d := d.(type) {
+	case cty.PathError:
+		ap := PathToAttributePath(d.Path)
+		diags = append(diags, &proto.Diagnostic{
+			Severity:  proto.Diagnostic_ERROR,
+			Summary:   d.Error(),
+			Attribute: ap,
+		})
 	case error:
 		diags = append(diags, &proto.Diagnostic{
 			Severity: proto.Diagnostic_ERROR,
@@ -86,3 +93,40 @@ func AttributePathToPath(ap *proto.AttributePath) cty.Path {
 	}
 	return p
 }
+
+// AttributePathToPath takes a cty.Path and converts it to a proto-encoded path.
+func PathToAttributePath(p cty.Path) *proto.AttributePath {
+	ap := &proto.AttributePath{}
+	for _, step := range p {
+		switch selector := step.(type) {
+		case cty.GetAttrStep:
+			ap.Steps = append(ap.Steps, &proto.AttributePath_Step{
+				Selector: &proto.AttributePath_Step_AttributeName{
+					AttributeName: selector.Name,
+				},
+			})
+		case cty.IndexStep:
+			key := selector.Key
+			switch key.Type() {
+			case cty.String:
+				ap.Steps = append(ap.Steps, &proto.AttributePath_Step{
+					Selector: &proto.AttributePath_Step_ElementKeyString{
+						ElementKeyString: key.AsString(),
+					},
+				})
+			case cty.Number:
+				v, _ := key.AsBigFloat().Int64()
+				ap.Steps = append(ap.Steps, &proto.AttributePath_Step{
+					Selector: &proto.AttributePath_Step_ElementKeyInt{
+						ElementKeyInt: v,
+					},
+				})
+			default:
+				// We'll bail early if we encounter anything else, and just
+				// return the valid prefix.
+				return ap
+			}
+		}
+	}
+	return ap
+}