Add check for utility subfolder in recursive layout library

check/checkconfigurations/checkconfigurations.go

@@ -1031,6 +1031,21 @@ var configurations = []Type{
 		ErrorModes:      []checkmode.Type{checkmode.Default},
 		CheckFunction:   checkfunctions.IncorrectExtrasFolderNameCase,
 	},
+	{
+		ProjectType:     projecttype.Library,
+		Category:        "structure",
+		Subcategory:     "",
+		ID:              "",
+		Brief:           "recursive with utility folder",
+		Description:     "",
+		MessageTemplate: `Utility folder found in "1.5" format library. Compilation of this folder is only supported on "1.0" format libraries. See: https://arduino.github.io/arduino-cli/latest/library-specification/#source-code`,
+		DisableModes:    nil,
+		EnableModes:     []checkmode.Type{checkmode.All},
+		InfoModes:       nil,
+		WarningModes:    []checkmode.Type{checkmode.Permissive},
+		ErrorModes:      []checkmode.Type{checkmode.Default},
+		CheckFunction:   checkfunctions.RecursiveLibraryWithUtilityFolder,
+	},
 	{
 		ProjectType:     projecttype.Sketch,
 		Category:        "structure",

check/checkfunctions/library.go

@@ -1064,6 +1064,19 @@ func MisspelledExtrasFolderName() (result checkresult.Type, output string) {
 	return checkresult.Pass, ""
 }
 
+// RecursiveLibraryWithUtilityFolder checks for presence of a `utility` subfolder in a recursive layout library.
+func RecursiveLibraryWithUtilityFolder() (result checkresult.Type, output string) {
+	if checkdata.LoadedLibrary().Layout == libraries.FlatLayout {
+		return checkresult.NotRun, ""
+	}
+
+	if checkdata.ProjectPath().Join("utility").Exist() {
+		return checkresult.Fail, ""
+	}
+
+	return checkresult.Pass, ""
+}
+
 // spellCheckLibraryPropertiesFieldValue returns the value of the provided library.properties field with commonly misspelled words corrected.
 func spellCheckLibraryPropertiesFieldValue(fieldName string) (result checkresult.Type, output string) {
 	if checkdata.LibraryPropertiesLoadError() != nil {

check/checkfunctions/library_test.go

@@ -349,3 +349,13 @@ func TestIncorrectExtrasFolderNameCase(t *testing.T) {
 
 	checkLibraryCheckFunction(IncorrectExtrasFolderNameCase, testTables, t)
 }
+
+func TestRecursiveLibraryWithUtilityFolder(t *testing.T) {
+	testTables := []libraryCheckFunctionTestTable{
+		{"Flat", "Flat", checkresult.NotRun, ""},
+		{"Recursive with utility", "RecursiveWithUtilityFolder", checkresult.Fail, ""},
+		{"Recursive without utility", "Recursive", checkresult.Pass, ""},
+	}
+
+	checkLibraryCheckFunction(RecursiveLibraryWithUtilityFolder, testTables, t)
+}

check/checkfunctions/testdata/libraries/RecursiveWithUtilityFolder/library.properties

@@ -0,0 +1,9 @@
+name=RecursiveWithUtilityFolder
+version=1.0.0
+author=Cristian Maglie <c.maglie@example.com>, Pippo Pluto <pippo@example.com>
+maintainer=Cristian Maglie <c.maglie@example.com>
+sentence=A library that makes coding a web server a breeze.
+paragraph=Supports HTTP1.1 and you can do GET and POST.
+category=Communication
+url=http://example.com/
+architectures=avr