What's the pattern for a language with optional semi colons?

[trusktr]

What may a grammar look like for a language with optional semi colons?

F.e. suppose you want to allow the following, where all of them are a function call:

foo (arg1, arg2);
// or
foo (arg1, arg2)
// or
foo
(arg1, arg2);
// or
foo
(arg1, arg2)

---

On a related note, I'm interested in code re-use. Are there any grammar files published somewhere that we can import and may have certain useful things for C-like or JS-like languages?

[msujew]

What may a grammar look like for a language with optional semi colons?

You can take a look at the langium-lox grammar. Even though it contains semi colons (due to them being mandatory in the original grammar), I just confirmed that the language also works as expected when making them optional.

On a related note, I'm interested in code re-use. Are there any grammar files published somewhere that we can import and may have certain useful things for C-like or JS-like languages?

Not yet, though we are thinking about that. We do have a few example languages, but nothing concrete such as a sort of "standard library" of Langium grammars.

[trusktr]

How does that look like? Can you perhaps push optional semis to a new branch in langium-lox, or paste the grammar here (or the diff)?

[msujew]

Sure, the changes are fairly minimal:

LoxElement: 
    Class |
    ExpressionBlock | 
    IfStatement |
    WhileStatement |
    ForStatement |
    FunctionDeclaration |
-    VariableDeclaration ';' | 
-    PrintStatement ';' | 
-    ReturnStatement ';' | 
-    Expression ';'
+    VariableDeclaration ';'? | 
+    PrintStatement ';'? | 
+    ReturnStatement ';'? | 
+    Expression ';'?
;

There are a few other places, such as for loops, which do have semi colons. However, they are mandatory for unambiguous parsing. Languages that do not use ;, usually opt for a for ... in ... { ... } syntax anyway instead of the for ;; syntax.