Add no-duplicate-extensions unit test

tests/no_duplicate_extensions.rs

@@ -0,0 +1,35 @@
+use std::collections::HashSet;
+
+use bat::assets::HighlightingAssets;
+
+#[test]
+fn no_duplicate_extensions() {
+    const KNOWN_EXCEPTIONS: &[&'static str] = &[
+        // The '.h' extension currently appears in multiple syntaxes: C, C++, Objective C,
+        // Objective C++
+        "h",
+        // In addition to the standard Haskell syntax in 'Packages', we also ship the 'Cabal'
+        // syntax which comes with a "Haskell (improved)" syntax.
+        "hs",
+        // In addition to the standard JavaScript syntax in 'Packages', we also ship the
+        // 'Javascript (Babel)' syntax.
+        "js",
+        // The "Ruby Haml" syntax also comes with a '.sass' extension. However, we make sure
+        // that 'sass' is mapped to the 'Sass' syntax.
+        "sass",
+    ];
+
+    let assets = HighlightingAssets::new();
+
+    let mut extensions = HashSet::new();
+
+    for syntax in assets.syntax_set.syntaxes() {
+        for extension in &syntax.file_extensions {
+            assert!(
+                KNOWN_EXCEPTIONS.contains(&extension.as_str()) || extensions.insert(extension),
+                "File extension / pattern \"{}\" appears twice in the syntax set",
+                extension
+            );
+        }
+    }
+}

tests/syntax_detection.rs

@@ -57,6 +57,17 @@ fn syntax_detection_basic() {
     assert_eq!(test.syntax_name("PKGBUILD"), "Bourne Again Shell (bash)");
 }
 
+#[test]
+fn syntax_detection_well_defined_mapping_for_duplicate_extensions() {
+    let test = SyntaxDetectionTest::new();
+
+    assert_eq!(test.syntax_name("test.sass"), "Sass");
+    // TODO: make these tests pass:
+    // assert_eq!(test.syntax_name("test.h"), "C");
+    // assert_eq!(test.syntax_name("test.hs"), "Haskell (Improved)");
+    // assert_eq!(test.syntax_name("test.js"), "JavaScript (Babel)");
+}
+
 #[test]
 fn syntax_detection_first_line() {
     let test = SyntaxDetectionTest::new();