table dashes communicate width

README.md

@@ -19,7 +19,7 @@ The dialect deviates from CommonMark for three reasons:
 ## Implemented syntax
 
 - Core block syntax: paragraphs, ATX headings, thematic breaks, block quotes, ordered/unordered lists, indented code, raw HTML, link reference definitions.
-- Tables: GFM/PHP Extra pipe tables with alignment. Use raw HTML for tables with row spans, column spans, or block content in cells. Table elements are included in the HTML subset.
+- Tables: GFM/PHP Extra pipe tables with alignment. Prefer explicit widths such as `{: colwidths="1fr 3fr"}`. Unequal separator dash counts provide shorthand (`-|---` requests a 25% / 75% split); equal counts leave sizing automatic. Explicit `colwidths` overrides dash widths. Use raw HTML for tables with row spans, column spans, or block content in cells. Table elements are included in the HTML subset.
 - GFM: task lists, `~~x~~` strikethrough, angle autolinks, and bare autolinks. Bare URL and email autolinking is on by default. Disable it with `bare_autolinks=False`. Explicit CommonMark angle autolinks remain enabled.
 - Code: backtick/tilde fenced code blocks, info strings, and Pandoc-style code attributes.
 - HTML-in-md: elements that `md` can emit, conventional phrasing tags (`u`, `kbd`, `b`, `i`, `ins`, `s`), and custom elements. Other tags render as literal text. `{=html}` raw blocks pass arbitrary HTML through.

docs/DIALECT.md

@@ -202,7 +202,7 @@ Fenced and indented code use `pre > code`. A language becomes a `language-*` cla
 
 ```markdown
 | Feature | Status | Notes |
-|:--------|:------:|------:|
+|:------|:------:|------:|
 | Tables  | ready  | yes   |
 ```
 
@@ -214,7 +214,11 @@ MDHTML:
 
 Pipe tables require a header. Cells use `align`; MDHTML deliberately retains `align` because it directly expresses the value converters need. Complex tables — row and column spans, block cell content, headerless bodies, footers — are written as raw HTML table soup, which is in the raw HTML subset; those cells carry `rowspan` and `colspan` as ordinary attributes.
 
-A table may carry mixed fixed and proportional widths as a `colwidths` attribute (`colwidths="1.2in 1fr 2fr"`, on a pipe table via its caption or IAL, or directly on a raw `<table>`). Lengths fix columns; `fr` tracks share the remaining width; the HTML exporter lowers the attribute to a `colgroup`. A `width` attribute on the table (same spellings) lowers to an inline style width: a CSS length verbatim, a bare number as px, an invalid value left as a visible attribute; it merges after `colwidths`' lowering, so an explicit width beats its `width:100%`. Non-HTML exporters ignore both.
+A table may carry mixed fixed and proportional widths as a `colwidths` attribute (`colwidths="1.2in 1fr 2fr"`, on a pipe table via its caption or IAL, or directly on a raw `<table>`). Lengths fix columns; `fr` tracks share the remaining width. The HTML exporter lowers the attribute to a `colgroup`; the Typst exporter uses the tracks directly.
+
+Unequal dash counts in a pipe table's separator row are shorthand for proportional `colwidths`: `-|---` sets `colwidths="1fr 3fr"`. Only dashes count; alignment colons and surrounding whitespace do not affect widths. Equal dash counts leave sizing automatic. Use an explicit attribute such as `{: colwidths="1fr 1fr"}` to request equal widths. Explicit `colwidths` overrides inferred widths. Inference applies regardless of source line length or cell content. Markdown export writes widths as an explicit attribute rather than reconstructing separator lengths.
+
+A `width` attribute on the table lowers to an inline style width: a CSS length verbatim, a bare number as px, an invalid value left as a visible attribute. It merges after `colwidths`' lowering, so an explicit width beats its `width:100%`. The Typst exporter ignores the table's `width` attribute.
 
 ## Definition lists and fenced divs
 
@@ -348,7 +352,7 @@ A caption line glued directly below a table becomes `caption`; its trailing attr
 
 ```markdown
 | Stage | Days |
-|:------|-----:|
+|:------|------:|
 | Ship  | 3    |
 : Delivery stages {#tbl-stages}
 ```

docs/sample.html

@@ -91,7 +91,7 @@ <h2>Block quotes and rules</h2>
 </blockquote>
 <h2>Tables</h2>
 <pre><code class="language-markdown">| Feature | Status | Notes |
-|:--------|:------:|------:|
+|:------|:------:|------:|
 | Tables | ready | aligned columns |
 | Math | ready | brackets mode |
 | HTML | ready | raw or markdown-enabled |
@@ -306,7 +306,7 @@ <h2>Captions and figures</h2>
 <pre><code class="language-markdown">![A cute puppy](puppy.jpg){#fig-diagram width="180"}
 
 | Stage | Days |
-|:------|-----:|
+|:------|------:|
 | Ship  | 3    |
 | Clear | 5    |
 : Delivery stages {#tbl-stages}
@@ -378,7 +378,7 @@ <h2>Template tokens and filling</h2>
 {{/office}}
 
 | Item | Qty |
-|------|-----|
+|------|------|
 {{#items}}
 | {{name}} | {{qty}} |
 {{/items}}

examples/sample-clean.md

@@ -73,7 +73,7 @@ Angle links work too: <https://example.com/spec>.
 ## Tables
 
 | Feature | Status | Notes |
-|:--------|:------:|------:|
+|:------|:------:|------:|
 | Tables | ready | aligned columns |
 | Math | ready | brackets mode |
 | HTML | ready | raw or markdown-enabled |
@@ -232,7 +232,7 @@ its trailing attribute list applies to the table:
 ![A cute puppy](puppy.jpg){#fig-diagram width="180"}
 
 | Stage | Days |
-|:------|-----:|
+|:------|------:|
 | Ship  | 3    |
 | Clear | 5    |
 : Delivery stages {#tbl-stages}
@@ -286,7 +286,7 @@ The {{name}} office ({{city}}) handles this matter.
 {{/office}}
 
 | Item | Qty |
-|------|-----|
+|------|------|
 {{#items}}
 | {{name}} | {{qty}} |
 {{/items}}

examples/sample-render.md

@@ -122,14 +122,14 @@ Angle links work too: <https://example.com/spec>.
 
 `````markdown
 | Feature | Status | Notes |
-|:--------|:------:|------:|
+|:------|:------:|------:|
 | Tables | ready | aligned columns |
 | Math | ready | brackets mode |
 | HTML | ready | raw or markdown-enabled |
 `````
 
 | Feature | Status | Notes |
-|:--------|:------:|------:|
+|:------|:------:|------:|
 | Tables | ready | aligned columns |
 | Math | ready | brackets mode |
 | HTML | ready | raw or markdown-enabled |
@@ -419,7 +419,7 @@ its trailing attribute list applies to the table:
 ![A cute puppy](puppy.jpg){#fig-diagram width="180"}
 
 | Stage | Days |
-|:------|-----:|
+|:------|------:|
 | Ship  | 3    |
 | Clear | 5    |
 : Delivery stages {#tbl-stages}
@@ -428,7 +428,7 @@ its trailing attribute list applies to the table:
 ![A cute puppy](puppy.jpg){#fig-diagram width="180"}
 
 | Stage | Days |
-|:------|-----:|
+|:------|------:|
 | Ship  | 3    |
 | Clear | 5    |
 : Delivery stages {#tbl-stages}
@@ -506,7 +506,7 @@ The {{name}} office ({{city}}) handles this matter.
 {{/office}}
 
 | Item | Qty |
-|------|-----|
+|------|------|
 {{#items}}
 | {{name}} | {{qty}} |
 {{/items}}
@@ -523,7 +523,7 @@ The {{name}} office ({{city}}) handles this matter.
 {{/office}}
 
 | Item | Qty |
-|------|-----|
+|------|------|
 {{#items}}
 | {{name}} | {{qty}} |
 {{/items}}

examples/sample.md

@@ -84,7 +84,7 @@ Angle links work too: <https://example.com/spec>.
 
 `````markdown
 | Feature | Status | Notes |
-|:--------|:------:|------:|
+|:------|:------:|------:|
 | Tables | ready | aligned columns |
 | Math | ready | brackets mode |
 | HTML | ready | raw or markdown-enabled |
@@ -271,7 +271,7 @@ its trailing attribute list applies to the table:
 ![A cute puppy](puppy.jpg){#fig-diagram width="180"}
 
 | Stage | Days |
-|:------|-----:|
+|:------|------:|
 | Ship  | 3    |
 | Clear | 5    |
 : Delivery stages {#tbl-stages}
@@ -333,7 +333,7 @@ The {{name}} office ({{city}}) handles this matter.
 {{/office}}
 
 | Item | Qty |
-|------|-----|
+|------|------|
 {{#items}}
 | {{name}} | {{qty}} |
 {{/items}}

src/block.rs

@@ -1432,7 +1432,7 @@ impl<'a> ContainerBuilder<'a> {
         let Some(header_line) = lines.last().cloned() else { return false };
         let paragraph_len = lines.len();
         let Some(header) = split_table_row(&header_line) else { return false };
-        let Some(aligns) = parse_table_separator(line) else { return false };
+        let Some((aligns, attrs)) = parse_table_separator(line) else { return false };
         if header.len() != aligns.len() { return false; }
         if self.record_trace {
             let lead = self.cur_offset + (line.len() - line.trim_start().len());
@@ -1443,7 +1443,7 @@ impl<'a> ContainerBuilder<'a> {
         }
         let head = header.into_iter().map(|cell| cell.trim().to_string()).collect();
         let table = BuildKind::Table {
-            attrs: Attr::default(),
+            attrs,
             caption: None,
             row_tokens: Vec::new(),
             head: vec![draft_inline_table_row(head, &aligns)],
@@ -3003,23 +3003,29 @@ fn raw_table_cells(line: &str) -> Vec<String> {
     cells
 }
 
-fn parse_table_separator(line: &str) -> Option<Vec<Align>> {
+fn parse_table_separator(line: &str) -> Option<(Vec<Align>, Attr)> {
     let cells = split_table_row(line)?;
     let mut aligns = Vec::new();
+    let mut widths = Vec::new();
     for cell in cells {
         let c = cell.trim();
         let left = c.starts_with(':');
         let right = c.ends_with(':');
         let dashes = c.trim_matches(':');
         if dashes.is_empty() || !dashes.chars().all(|x| x == '-') { return None; }
+        widths.push(dashes.len());
         aligns.push(match (left, right) {
             (true, true) => Align::Center,
             (true, false) => Align::Left,
             (false, true) => Align::Right,
             _ => Align::None,
         });
     }
-    Some(aligns)
+    let mut attrs = Attr::default();
+    if widths.windows(2).any(|w| w[0] != w[1]) {
+        attrs.set_pair("colwidths", widths.iter().map(|w| format!("{w}fr")).collect::<Vec<_>>().join(" "));
+    }
+    Some((aligns, attrs))
 }
 
 pub(crate) fn paragraph_interrupts(line: &str) -> bool { starts_block(line) || list_interrupts_paragraph(line) || def_marker(line).is_some() }

tests/canonical.rs

@@ -12,6 +12,17 @@ fn panel_titles_and_nested_panels_roundtrip() {
     assert!(!html.contains("<h2") && !html.contains("<h3"));
 }
 
+#[test]
+fn table_dash_widths_roundtrip() {
+    let source = "| A | B |\n|:---|---------:|\n| x | y |\n";
+    let options = Options::default();
+    let document = parse(source, &options);
+    let html = render(&document);
+    assert!(html.contains(r#"colwidths="3fr 9fr""#));
+    let canonical = render_md(&document);
+    assert_eq!(render(&parse(&canonical, &options)), html);
+}
+
 #[test]
 fn canonical_markdown_preserves_mdhtml_tree() {
     let source = r#"---

tests/fixtures/dialect.md

@@ -5,7 +5,7 @@ A paragraph with *em*, **strong**, ~~gone~~, H~2~O, [a link](https://example.com
 [^n]: Footnote *body*.
 
 | Left | Right | Center |
-|:-----|------:|:------:|
+|:------|------:|:------:|
 | a | b | c |
 
 Term

tests/source/cmark-gfm/extensions.txt

@@ -44,7 +44,7 @@ textual alignment of the columns is shown to be irrelevant.
 Hello!
 
 | _abc_ | セン |
-| ----- | ---- |
+| ----- | ----- |
 | 1. Block elements inside cells don't work. | |
 | But _**inline elements do**_. | x |
 
@@ -81,7 +81,7 @@ Here we demonstrate some edge cases about what is and isn't a table.
 | Not enough table | to be considered table |
 
 | Just enough table | to be considered table |
-| ----------------- | ---------------------- |
+| ---------------------- | ---------------------- |
 
 | ---- | --- |
 
@@ -149,7 +149,7 @@ the end:
 Hello!
 
 | _abc_ | セン |
-| ----- | ---- |
+| ----- | ----- |
 | this row has a space at the end | | 
 | But _**inline elements do**_. | x |
 
@@ -181,7 +181,7 @@ Table alignment:
 
 ```````````````````````````````` example
 aaa | bbb | ccc | ddd | eee
-:-- | --- | :-: | --- | --:
+:--- | --- | :---: | --- | ---:
 fff | ggg | hhh | iii | jjj
 .
 <table>

tests/source/cmark-gfm/spec.txt

@@ -3376,7 +3376,7 @@ they are. Likewise, use of leading and trailing pipes may be inconsistent:
 
 ```````````````````````````````` example table
 | abc | defghi |
-:-: | -----------:
+:-: | -:
 bar | baz
 .
 <table>

tests/source/php-markdown-extra.mdtest/Tables.text

@@ -60,7 +60,7 @@ Table alignement:
 Table alignement (alternate spacing):
 
 | Default   | Right     |  Center   |     Left  |
-| --------- | :-------- | :-------: | --------: |
+| -------   | :-------  | :-------: | -------:  |
 | Long Cell | Long Cell | Long Cell | Long Cell |
 | Cell      | Cell      |   Cell    |     Cell  |
 

tests/test_focused.py

@@ -140,6 +140,30 @@ def test_table_ial_line_attaches():
     assert html.startswith('<table class="c">')
     assert '{: .c}' not in html
 
+
+def test_table_dash_widths():
+    from mdhtml import mdhtml2md
+    for sep, widths in (("|---|---------|", "3fr 9fr"), (" :--- | ---------: ", "3fr 9fr"), ("|:-:|---|", "1fr 3fr")):
+        src = f"| A | B |\n{sep}\n| x | [link](https://example.com) |\n"
+        html = md2mdhtml(src)
+        assert f'colwidths="{widths}"' in html
+        assert_html(html, md2mdhtml(src + f'{{: colwidths="{widths}"}}'))
+        assert_html(md2mdhtml(mdhtml2md(html)), html)
+    nested = "> - | A | B |\n>   |:---|---------:|\n>   | x | y |\n"
+    assert 'colwidths="3fr 9fr"' in md2mdhtml(nested)
+
+
+def test_table_dash_widths_auto_and_explicit():
+    for sep in ("|---|---|", "|:---|---:|", "|:---:| --- |", "|------|------|"):
+        assert "colwidths" not in md2mdhtml(f"| A | B |\n{sep}\n| x | y |\n")
+    assert "colwidths" not in md2mdhtml("| A |\n|:-----:|\n| x |\n")
+    src = "| A | B |\n|---|---------|\n| x | y |\n"
+    ial = '{: colwidths="1fr 1fr"}'
+    for authored in (ial + "\n" + src, src + ial, src + ': Caption {colwidths="1fr 1fr"}'):
+        html = md2mdhtml(authored)
+        assert 'colwidths="1fr 1fr"' in html
+        assert 'colwidths="3fr 9fr"' not in html
+
 def test_raw_attribute_blocks_and_inlines():
     html = md2mdhtml('```{=docx}\n<w:br w:type="page"/>\n```\n')
     assert html == '<script type="application/vnd.mdhtml.raw" data-format="docx"><w:br w:type="page"/>\n</script>\n'