Fix empty 2-d math args with whitespace/trivia (#3786)

Co-authored-by: Laurenz <laurmaedje@gmail.com>

crates/typst-syntax/src/parser.rs

@@ -592,10 +592,23 @@ fn math_args(p: &mut Parser) {
     p.wrap(m, SyntaxKind::Args);
 }
 
+/// Wrap math function arguments in a "Math" SyntaxKind to combine adjacent expressions
+/// or create blank content.
+///
+/// We don't wrap when `exprs == 1`, as there is only one expression, so the grouping
+/// isn't needed, and this would change the type of the expression from potentially
+/// non-content to content.
+///
+/// Note that `exprs` might be 0 if we have whitespace or trivia before a comma i.e.
+/// `mat(; ,)` or `sin(x, , , ,)`. This would create an empty Math element before that
+/// trivia if we called `p.wrap()` -- breaking the expected AST for 2-d arguments -- so
+/// we instead manually wrap to our current marker using `p.wrap_within()`.
 fn maybe_wrap_in_math(p: &mut Parser, arg: Marker, named: Option<Marker>) {
     let exprs = p.post_process(arg).filter(|node| node.is::<ast::Expr>()).count();
     if exprs != 1 {
-        p.wrap(arg, SyntaxKind::Math);
+        // Convert 0 exprs into a blank math element (so empty arguments are allowed).
+        // Convert 2+ exprs into a math element (so they become a joined sequence).
+        p.wrap_within(arg, p.marker(), SyntaxKind::Math);
     }
 
     if let Some(m) = named {

tests/suite/math/call.typ

@@ -0,0 +1,97 @@
+// Test math function call edge cases.
+
+// Note: 2d argument calls are tested for matrices in `mat.typ`
+
+--- math-call-non-func ---
+$ pi(a) $
+$ pi(a,) $
+$ pi(a,b) $
+$ pi(a,b,) $
+
+--- math-call-repr ---
+#let args(..body) = body
+#let check(it, r) = test-repr(it.body.text, r)
+#check($args(a)$, "([a])")
+#check($args(a,)$, "([a])")
+#check($args(a,b)$, "([a], [b])")
+#check($args(a,b,)$, "([a], [b])")
+#check($args(,a,b,,,)$, "([], [a], [b], [], [])")
+
+--- math-call-2d-non-func ---
+// Error: 6-7 expected content, found array
+// Error: 8-9 expected content, found array
+$ pi(a;b) $
+
+--- math-call-2d-semicolon-priority ---
+// If the semicolon directlry follows a hash expression, it terminates that
+// instead of indicating 2d arguments.
+$ mat(#"math" ; "wins") $
+$ mat(#"code"; "wins") $
+
+--- math-call-2d-repr ---
+#let args(..body) = body
+#let check(it, r) = test-repr(it.body.text, r)
+#check($args(a;b)$, "(([a],), ([b],))")
+#check($args(a,b;c)$, "(([a], [b]), ([c],))")
+#check($args(a,b;c,d;e,f)$, "(([a], [b]), ([c], [d]), ([e], [f]))")
+
+--- math-call-2d-repr-structure ---
+#let args(..body) = body
+#let check(it, r) = test-repr(it.body.text, r)
+#check($args( a; b; )$, "(([a],), ([b],))")
+#check($args(a;  ; c)$, "(([a],), ([],), ([c],))")
+#check($args(a b,/**/; b)$, "((sequence([a], [ ], [b]), []), ([b],))")
+#check($args(a/**/b, ; b)$, "((sequence([a], [b]), []), ([b],))")
+#check($args( ;/**/a/**/b/**/; )$, "(([],), (sequence([a], [b]),))")
+#check($args( ; , ; )$, "(([],), ([], []))")
+#check($args(/**/; // funky whitespace/trivia
+    ,   /**/  ;/**/)$, "(([],), ([], []))")
+
+--- math-call-empty-args-non-func ---
+// Trailing commas and empty args introduce blank content in math
+$ sin(,x,y,,,) $
+// with whitespace/trivia:
+$ sin( ,/**/x/**/, , /**/y, ,/**/, ) $
+
+--- math-call-empty-args-repr ---
+#let args(..body) = body
+#let check(it, r) = test-repr(it.body.text, r)
+#check($args(,x,,y,,)$, "([], [x], [], [y], [])")
+// with whitespace/trivia:
+#check($args( ,/**/x/**/, , /**/y, ,/**/, )$, "([], [x], [], [y], [], [])")
+
+--- math-call-value-non-func ---
+$ sin(1) $
+// Error: 8-9 expected content, found integer
+$ sin(#1) $
+
+--- math-call-pass-to-box ---
+// When passing to a function, we lose the italic styling if we wrap the content
+// in a non-math function unless it's already nested in some math element (lr,
+// attach, etc.)
+//
+// This is not good, so this test should fail and be updated once it is fixed.
+#let id(body) = body
+#let bx(body) = box(body, stroke: blue+0.5pt, inset: (x:2pt, y:3pt))
+#let eq(body) = math.equation(body)
+$
+     x y   &&quad     x (y z)   &quad     x y^z  \
+  id(x y)  &&quad  id(x (y z))  &quad  id(x y^z) \
+  eq(x y)  &&quad  eq(x (y z))  &quad  eq(x y^z) \
+  bx(x y)  &&quad  bx(x (y z))  &quad  bx(x y^z) \
+$
+
+--- issue-3774-math-call-empty-2d-args ---
+$ mat(;,) $
+// Add some whitespace/trivia:
+$ mat(; ,) $
+$ mat(;/**/,) $
+$ mat(;
+,) $
+$ mat(;// line comment
+,) $
+$ mat(
+  1, , ;
+   ,1, ;
+   , ,1;
+) $

tests/suite/math/syntax.typ

@@ -1,16 +1,10 @@
 // Test math syntax.
 
---- math-call-non-func ---
-$ pi(a) $
-$ pi(a,) $
-$ pi(a,b) $
-$ pi(a,b,) $
-
 --- math-unicode ---
 // Test Unicode math.
 $ ∑_(i=0)^ℕ a ∘ b = \u{2211}_(i=0)^NN a compose b $
 
---- math-shorthandes ---
+--- math-shorthands ---
 // Test a few shorthands.
 $ underline(f' : NN -> RR) \
   n |-> cases(