improve header/footer expansion error message

crates/typst-library/src/layout/grid/resolve.rs

@@ -908,11 +908,21 @@ struct CellGridResolver<'a, 'b, 'x> {
     span: Span,
 }
 
+#[derive(Debug, Clone, Copy)]
 enum RowGroupKind {
     Header,
     Footer,
 }
 
+impl RowGroupKind {
+    fn name(self) -> &'static str {
+        match self {
+            Self::Header => "header",
+            Self::Footer => "footer",
+        }
+    }
+}
+
 struct RowGroupData {
     /// The range of rows of cells inside this grid row group. The
     /// first and last rows are guaranteed to have cells (an exception
@@ -1456,11 +1466,14 @@ impl<'x> CellGridResolver<'_, '_, 'x> {
 
             // Cell's header or footer must expand to include the cell's
             // occupied positions, if possible.
-            if let Some(RowGroupData { range: group_range, .. }) = &mut row_group_data {
+            if let Some(RowGroupData { range: group_range, kind, .. }) =
+                &mut row_group_data
+            {
                 *group_range = Some(
                     expand_row_group(
                         resolved_cells,
                         group_range.as_ref(),
+                        *kind,
                         first_available_row,
                         y,
                         rowspan,
@@ -1683,6 +1696,7 @@ impl<'x> CellGridResolver<'_, '_, 'x> {
 fn expand_row_group(
     resolved_cells: &[Option<Entry<'_>>],
     group_range: Option<&Range<usize>>,
+    group_kind: RowGroupKind,
     first_available_row: usize,
     cell_y: usize,
     rowspan: usize,
@@ -1706,9 +1720,10 @@ fn expand_row_group(
     // 'y = 1' is the earliest row it can occupy.
     if new_group_start < first_available_row {
         bail!(
-            "cell would cause header or footer to expand to non-empty row {}",
+            "cell would cause {} to expand to non-empty row {}",
+            group_kind.name(),
             first_available_row.saturating_sub(1);
-            hint: "try moving its cells to later rows"
+            hint: "try moving its cells to available rows"
         );
     }
 
@@ -1770,23 +1785,11 @@ fn expand_row_group(
             .map(|cells| &cells[..columns.min(cells.len())])
         {
             if new_row.iter().any(Option::is_some) {
-                // TODO:
+                bail!(
-                // - Later/earlier rows might be confusing
+                    "cell would cause {} to expand to non-empty row {new_y}",
-                // (moving to the end always works...)
+                    group_kind.name();
-                // - Detect when header or footer collided with
+                    hint: "try moving its cells to available rows",
-                // another header or footer and provide a
+                )
-                // better error message if so.
-                if group_range.is_none_or(|r| new_y < r.start) {
-                    bail!(
-                        "cell would cause header or footer to expand to non-empty row {new_y}";
-                        hint: "try moving its cells to later rows"
-                    );
-                } else {
-                    bail!(
-                        "cell would cause header or footer to expand to non-empty row {new_y}";
-                        hint: "try moving its cells to earlier rows"
-                    );
-                }
             }
         } else {
             // Received 'None' or an empty slice, so we are expanding the

tests/suite/layout/grid/footers.typ

@@ -458,8 +458,8 @@
   table.footer(
     table.hline(stroke: red),
     table.hline(y: 1, stroke: aqua),
-    // Error: 5-24 cell would cause header or footer to expand to non-empty row 0
+    // Error: 5-24 cell would cause footer to expand to non-empty row 0
-    // Hint: 5-24 try moving its cells to later rows
+    // Hint: 5-24 try moving its cells to available rows
     table.cell(y: 0)[b],
     [c]
   )
@@ -474,8 +474,8 @@
   table.cell(y: 1)[a],
   table.footer(
     [b], [c],
-    // Error: 6-7 cell would cause header or footer to expand to non-empty row 1
+    // Error: 6-7 cell would cause footer to expand to non-empty row 1
-    // Hint: 6-7 try moving its cells to earlier rows
+    // Hint: 6-7 try moving its cells to available rows
     [d],
   ),
 )
@@ -489,8 +489,8 @@
   table.cell(y: 2)[a],
   table.footer(
     [b], [c],
-    // Error: 5-24 cell would cause header or footer to expand to non-empty row 2
+    // Error: 5-24 cell would cause footer to expand to non-empty row 2
-    // Hint: 5-24 try moving its cells to earlier rows
+    // Hint: 5-24 try moving its cells to available rows
     table.cell(y: 3)[d],
   ),
 )
@@ -500,8 +500,8 @@
   columns: 2,
   table.header(),
   table.footer(
-    // Error: 5-24 cell would cause header or footer to expand to non-empty row 0
+    // Error: 5-24 cell would cause footer to expand to non-empty row 0
-    // Hint: 5-24 try moving its cells to later rows
+    // Hint: 5-24 try moving its cells to available rows
     table.cell(y: 0)[a]
   ),
 )

tests/suite/layout/grid/headers.typ

@@ -403,8 +403,8 @@
   table.header(
     table.hline(stroke: red),
     table.hline(y: 1, stroke: aqua),
-    // Error: 5-24 cell would cause header or footer to expand to non-empty row 0
+    // Error: 5-24 cell would cause header to expand to non-empty row 0
-    // Hint: 5-24 try moving its cells to later rows
+    // Hint: 5-24 try moving its cells to available rows
     table.cell(y: 0)[b],
     [c]
   )
@@ -423,8 +423,8 @@
   table.header(
     table.hline(stroke: red),
     table.hline(y: 3, stroke: aqua),
-    // Error: 5-24 cell would cause header or footer to expand to non-empty row 2
+    // Error: 5-24 cell would cause header to expand to non-empty row 2
-    // Hint: 5-24 try moving its cells to later rows
+    // Hint: 5-24 try moving its cells to available rows
     table.cell(y: 2)[b],
   )
 )
@@ -438,8 +438,8 @@
   table.cell(y: 1)[a],
   table.header(
     [b], [c],
-    // Error: 6-7 cell would cause header or footer to expand to non-empty row 1
+    // Error: 6-7 cell would cause header to expand to non-empty row 1
-    // Hint: 6-7 try moving its cells to earlier rows
+    // Hint: 6-7 try moving its cells to available rows
     [d],
   ),
 )
@@ -453,8 +453,8 @@
   table.cell(y: 2)[a],
   table.header(
     [b], [c],
-    // Error: 5-24 cell would cause header or footer to expand to non-empty row 2
+    // Error: 5-24 cell would cause header to expand to non-empty row 2
-    // Hint: 5-24 try moving its cells to earlier rows
+    // Hint: 5-24 try moving its cells to available rows
     table.cell(y: 3)[d],
   ),
 )