Support shebangs in scripts.

CHANGELOG.md

@@ -32,6 +32,8 @@ Breaking changes
 * `protected`, `super` are now reserved keywords.
 * The `Module::set_fn_XXX` API now take `&str` as the function name instead of `Into<String>`.
 * The _reflections_ API such as `Engine::gen_fn_signatures`, `Module::update_fn_metadata` etc. are put under the `metadata` feature gate.
+* The shebang `#!` is now a reserved symbol.
+* Shebangs at the very beginning of script files are skipped when loading them.
 
 Enhancements
 ------------
@@ -39,6 +41,7 @@ Enhancements
 * Replaced all `HashMap` usage with `BTreeMap` for better performance because collections in Rhai are tiny.
 * `Engine::register_result_fn` no longer requires the successful return type to be `Dynamic`.  It can now be any clonable type.
 * `#[rhai_fn(return_raw)]` can now return `Result<T, Box<EvalAltResult>>` where `T` is any clonable type instead of `Result<Dynamic, Box<EvalAltResult>>`.
+* Rhai scripts can now start with a shebang `#!`.
 
 
 Version 0.19.14

src/bin/rhai-run.rs

@@ -58,13 +58,20 @@ fn main() {
             exit(1);
         }
 
-        if let Err(err) = engine.consume(&contents) {
+        let contents = if contents.starts_with("#!") {
+            // Skip shebang
+            &contents[contents.find('\n').unwrap_or(0)..]
+        } else {
+            &contents[..]
+        };
+
+        if let Err(err) = engine.consume(contents) {
             eprintln!("{:=<1$}", "", filename.len());
             eprintln!("{}", filename);
             eprintln!("{:=<1$}", "", filename.len());
             eprintln!("");
 
-            eprint_error(&contents, *err);
+            eprint_error(contents, *err);
         }
     }
 }

src/engine_api.rs

@@ -1185,6 +1185,15 @@ impl Engine {
             )
         })?;
 
+        if contents.starts_with("#!") {
+            // Remove shebang
+            if let Some(n) = contents.find('\n') {
+                contents.drain(0..n).count();
+            } else {
+                contents.clear();
+            }
+        };
+
         Ok(contents)
     }
     /// Compile a script file into an [`AST`], which can be used later for evaluation.

src/token.rs

@@ -587,11 +587,13 @@ impl Token {
             #[cfg(feature = "no_module")]
             "import" | "export" | "as" => Reserved(syntax.into()),
 
-            "===" | "!==" | "->" | "<-" | ":=" | "~" | "::<" | "(*" | "*)" | "#" | "public"
-            | "protected" | "super" | "new" | "use" | "module" | "package" | "var" | "static"
-            | "begin" | "end" | "shared" | "with" | "each" | "then" | "goto" | "unless"
-            | "exit" | "match" | "case" | "default" | "void" | "null" | "nil" | "spawn"
-            | "thread" | "go" | "sync" | "async" | "await" | "yield" => Reserved(syntax.into()),
+            "===" | "!==" | "->" | "<-" | ":=" | "~" | "::<" | "(*" | "*)" | "#" | "#!"
+            | "public" | "protected" | "super" | "new" | "use" | "module" | "package" | "var"
+            | "static" | "begin" | "end" | "shared" | "with" | "each" | "then" | "goto"
+            | "unless" | "exit" | "match" | "case" | "default" | "void" | "null" | "nil"
+            | "spawn" | "thread" | "go" | "sync" | "async" | "await" | "yield" => {
+                Reserved(syntax.into())
+            }
 
             KEYWORD_PRINT | KEYWORD_DEBUG | KEYWORD_TYPE_OF | KEYWORD_EVAL | KEYWORD_FN_PTR
             | KEYWORD_FN_PTR_CALL | KEYWORD_FN_PTR_CURRY | KEYWORD_THIS | KEYWORD_IS_DEF_VAR => {
@@ -1323,6 +1325,9 @@ fn get_next_token_inner(
                 eat_next(stream, pos);
                 return Some((Token::MapStart, start_pos));
             }
+            // Shebang
+            ('#', '!') => return Some((Token::Reserved("#!".into()), start_pos)),
+
             ('#', _) => return Some((Token::Reserved("#".into()), start_pos)),
 
             // Operators