Simplify findNonSourceFiles, fix its documentation

Author: ViktorSimko

Sources/Xcodeproj/generate().swift

@@ -74,12 +74,10 @@ public func generate(
     // Find non-source files in the source directories and root that should be added
     // as a reference to the project.
     var extraFiles = try findNonSourceFiles(path: srcroot)
-    if let sourcesExtraFiles = try? findNonSourceFiles(path: srcroot.appending(component: "Sources"), recursively: true) {
-        extraFiles.append(contentsOf: sourcesExtraFiles)
-    }
-    if let testsExtraFiles = try? findNonSourceFiles(path: srcroot.appending(component: "Tests"), recursively: true) {
-        extraFiles.append(contentsOf: testsExtraFiles)
-    }
+    let sourcesExtraFiles = try findNonSourceFiles(path: srcroot.appending(component: "Sources"), recursively: true)
+    extraFiles.append(contentsOf: sourcesExtraFiles)
+    let testsExtraFiles = try findNonSourceFiles(path: srcroot.appending(component: "Tests"), recursively: true)
+    extraFiles.append(contentsOf: testsExtraFiles)
 
     // Get the ignored files and exclude them
     let ignoredFiles = try repositoryProvider.openCheckout(at: srcroot).getIgnoredFiles()
@@ -200,15 +198,17 @@ func findDirectoryReferences(path: AbsolutePath) throws -> [AbsolutePath] {
     })
 }
 
-/// Finds the non-source files from `path` recursively
+/// Finds the non-source files from `path`
+/// - parameters:
+///   - path: The path of the directory to get the files from
+///   - recursively: Specifies if the directory at `path` should be searched recursively
 func findNonSourceFiles(path: AbsolutePath, recursively: Bool = false) throws -> [AbsolutePath] {
     let filesFromPath = try walk(path, recursively: recursively)
 
     return filesFromPath.filter {
         if !isFile($0) { return false }
-        if let `extension` = $0.extension {
-            if SupportedLanguageExtension.cFamilyExtensions.contains(`extension`) { return false }
-            if SupportedLanguageExtension.swiftExtensions.contains(`extension`) { return false }
+        if let `extension` = $0.extension, SupportedLanguageExtension.validExtensions.contains(`extension`) {
+            return false
         }
         return true
     }