Add check for incorrect library extras folder name case

Author: per1234

check/checkconfigurations/checkconfigurations.go

@@ -1001,6 +1001,21 @@ var configurations = []Type{
 		ErrorModes:      nil,
 		CheckFunction:   checkfunctions.MisspelledExtrasFolderName,
 	},
+	{
+		ProjectType:     projecttype.Library,
+		Category:        "structure",
+		Subcategory:     "",
+		ID:              "",
+		Brief:           "incorrect extras folder name case",
+		Description:     "",
+		MessageTemplate: "Incorrect extras folder name case: {{.}}. See: https://arduino.github.io/arduino-cli/latest/library-specification/#extra-documentation",
+		DisableModes:    nil,
+		EnableModes:     []checkmode.Type{checkmode.All},
+		InfoModes:       nil,
+		WarningModes:    []checkmode.Type{checkmode.Permissive},
+		ErrorModes:      []checkmode.Type{checkmode.Default},
+		CheckFunction:   checkfunctions.IncorrectExtrasFolderNameCase,
+	},
 	{
 		ProjectType:     projecttype.Sketch,
 		Category:        "structure",

check/checkfunctions/library.go

@@ -1073,6 +1073,22 @@ func spellCheckLibraryPropertiesFieldValue(fieldName string) (result checkresult
 	return checkresult.Pass, ""
 }
 
+// IncorrectExtrasFolderNameCase checks for incorrect `extras` folder name case.
+func IncorrectExtrasFolderNameCase() (result checkresult.Type, output string) {
+	directoryListing, err := checkdata.ProjectPath().ReadDir()
+	if err != nil {
+		panic(err)
+	}
+	directoryListing.FilterDirs()
+
+	path, found := containsIncorrectPathBaseCase(directoryListing, "extras")
+	if found {
+		return checkresult.Fail, path.String()
+	}
+
+	return checkresult.Pass, ""
+}
+
 // nameInLibraryManagerIndex returns whether there is a library in Library Manager index using the given name.
 func nameInLibraryManagerIndex(name string) bool {
 	libraries := checkdata.LibraryManagerIndex()["libraries"].([]interface{})

check/checkfunctions/library_test.go

@@ -330,3 +330,13 @@ func TestMisspelledExtrasFolderName(t *testing.T) {
 
 	checkLibraryCheckFunction(MisspelledExtrasFolderName, testTables, t)
 }
+
+func TestIncorrectExtrasFolderNameCase(t *testing.T) {
+	testTables := []libraryCheckFunctionTestTable{
+		{"Correct case", "ExtrasFolder", checkresult.Pass, ""},
+		{"Incorrect case", "IncorrectExtrasFolderCase", checkresult.Fail, ""},
+		{"No extras folder", "Recursive", checkresult.Pass, ""},
+	}
+
+	checkLibraryCheckFunction(IncorrectExtrasFolderNameCase, testTables, t)
+}

check/checkfunctions/testdata/libraries/IncorrectExtrasFolderCase/EXTRAS/.gitkeep

@@ -0,0 +1,9 @@
+name=IncorrectExtrasFolderCase
+version=1.0.0
+author=Cristian Maglie <[email protected]>, Pippo Pluto <[email protected]>
+maintainer=Cristian Maglie <[email protected]>
+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