Add check for incorrect library src subfolder name case

Author: per1234

Diff for: check/checkconfigurations/checkconfigurations.go

@@ -971,6 +971,21 @@ var configurations = []Type{
 		ErrorModes:      []checkmode.Type{checkmode.Default},
 		CheckFunction:   checkfunctions.LibraryFolderNameGTMaxLength,
 	},
+	{
+		ProjectType:     projecttype.Library,
+		Category:        "structure",
+		Subcategory:     "",
+		ID:              "",
+		Brief:           "incorrect src folder case",
+		Description:     "",
+		MessageTemplate: "Incorrect src folder case. This will cause the library to not be recognized on case-sensitive operating systems. See: https://arduino.github.io/arduino-cli/latest/library-specification/#library-root-folder",
+		DisableModes:    nil,
+		EnableModes:     []checkmode.Type{checkmode.Default},
+		InfoModes:       nil,
+		WarningModes:    nil,
+		ErrorModes:      []checkmode.Type{checkmode.Default},
+		CheckFunction:   checkfunctions.IncorrectLibrarySrcFolderNameCase,
+	},
 	{
 		ProjectType:     projecttype.Library,
 		Category:        "structure",

Diff for: check/checkfunctions/library.go

@@ -1008,6 +1008,28 @@ func LibraryFolderNameGTMaxLength() (result checkresult.Type, output string) {
 	return checkresult.Pass, ""
 }
 
+// IncorrectLibrarySrcFolderNameCase checks for incorrect case of src subfolder name in recursive format libraries.
+func IncorrectLibrarySrcFolderNameCase() (result checkresult.Type, output string) {
+	if library.ContainsMetadataFile(checkdata.ProjectPath()) && library.ContainsHeaderFile(checkdata.ProjectPath()) {
+		// Flat layout, so no special treatment of src subfolder.
+		return checkresult.NotRun, ""
+	}
+
+	// The library is intended to have the recursive layout.
+	directoryListing, err := checkdata.ProjectPath().ReadDir()
+	if err != nil {
+		panic(err)
+	}
+	directoryListing.FilterDirs()
+
+	path, found := containsIncorrectPathBaseCase(directoryListing, "src")
+	if found {
+		return checkresult.Fail, path.String()
+	}
+
+	return checkresult.Pass, ""
+}
+
 // MisspelledExamplesFolderName checks for incorrectly spelled `examples` folder name.
 func MisspelledExamplesFolderName() (result checkresult.Type, output string) {
 	directoryListing, err := checkdata.ProjectPath().ReadDir()

Diff for: check/checkfunctions/library_test.go

@@ -310,6 +310,16 @@ func TestLibraryFolderNameGTMaxLength(t *testing.T) {
 	checkLibraryCheckFunction(LibraryFolderNameGTMaxLength, testTables, t)
 }
 
+func TestIncorrectLibrarySrcFolderNameCase(t *testing.T) {
+	testTables := []libraryCheckFunctionTestTable{
+		{"Flat, not precompiled", "Flat", checkresult.NotRun, ""},
+		{"Incorrect case", "IncorrectSrcFolderNameCase", checkresult.Fail, ""},
+		{"Correct case", "Recursive", checkresult.Pass, ""},
+	}
+
+	checkLibraryCheckFunction(IncorrectLibrarySrcFolderNameCase, testTables, t)
+}
+
 func TestMisspelledExamplesFolderName(t *testing.T) {
 	testTables := []libraryCheckFunctionTestTable{
 		{"Correctly spelled", "ExamplesFolder", checkresult.Pass, ""},

Diff for: check/checkfunctions/testdata/libraries/IncorrectSrcFolderNameCase/SRC/IncorrectSrcFolderNameCase.h

@@ -0,0 +1,9 @@
+name=IncorrectSrcFolderNameCase
+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