[language-html] Allow for folding of attribute lists…

…such as in multi-line self-closing tags and multi-line opening tags.

Also fix an issue in fold handling that made it impossible to use `@_IGNORE_` captures in `folds.scm`.

Author: savetheclocktower

packages/language-html/grammars/tree-sitter-html/folds.scm

@@ -1,6 +1,74 @@
+; When dealing with a self-closing element that spans multiple lines, this lets
+; us fold the attribute list.
+;
+; This query captures elements that happen to be self-closing but don't end
+; with an XHTML-style ` />`. Because `tree-sitter-html` doesn't distinguish
+; these from elements that can have content, we have to check the tag name to
+; know how to treat these.
+
+((element
+  (start_tag
+    (tag_name) @_IGNORE_) @fold)
+  (#match? @_IGNORE_ "^(area|base|br|col|embed|hr|img|input|keygen|link|meta|param|source|track|wbr)$")
+)
+
+; This one captures the XHTML-style nodes.
+(self_closing_tag) @fold
+
+
+; TODO: Right now, the fold cache doesn't work properly when a given range
+; satisfies more than one fold. We should employ `ScopeResolver` to fix this.
+
+; Fold up all of
+;
+; <div
+;   foo="bar"
+;   baz="thud">
+;
+; </div>
+;
+; with the fold indicator appearing on whichever line has the `>` that closes
+; the opening tag.
+;
+; Usually this'll be the same line on which the tag opened; but when it isn't,
+; this allows for the attribute list of the opening element to be folded
+; separately from the element's contents.
+;
+
+(element
+  (start_tag
+    (tag_name) @_IGNORE_
+     ">" @fold)
+  (#not-match? @_IGNORE_ "^(area|base|br|col|embed|hr|img|input|keygen|link|meta|param|source|track|wbr)$")
+  (#set! fold.endAt parent.parent.lastNamedChild.startPosition)
+  (#set! fold.adjustToEndOfPreviousRow true)
+)
+
+
+; When we have…
+;
+; <div
+;   foo="bar"
+;   baz="thud"
+; >
+;
+; </div>
+;
+; …we can put a fold indicator on the line with `<div` and use it to fold up
+; all of a start tag's attributes.
+;
+; We keep the end of the fold on a separate line because otherwise we lose the
+; ability to independently toggle the folding of the element's contents.
+;
+(element
+  (start_tag
+    (tag_name) @_IGNORE_) @fold
+  (#not-match? @_IGNORE_ "^(area|base|br|col|embed|hr|img|input|keygen|link|meta|param|source|track|wbr)$")
+  (#set! fold.endAt lastChild.startPosition)
+  (#set! fold.adjustToEndOfPreviousRow true))
+
 
 [
-  (element)
   (script_element)
   (style_element)
 ] @fold

src/wasm-tree-sitter-language-mode.js

@@ -2149,14 +2149,17 @@ class FoldResolver {
     let boundaries = createTree(compareBoundaries);
     let captures = this.layer.foldsQuery.captures(rootNode, start, end);
 
+    // TODO: When a node is captured more than once, we handle all captures. We
+    // should instead use `ScopeResolver` so that a single folds query can use
+    // `capture.final` and `capture.shy` to rule out other possible matches.
     for (let capture of captures) {
       if (capture.node.startPosition.row < start.row) { continue; }
       if (capture.name === 'fold') {
         boundaries = boundaries.insert({
           position: capture.node.startPosition,
           boundary: 'start'
         }, capture);
-      } else {
+      } else if (capture.name.startsWith('fold.')) {
         let key = this.keyForDividedFold(capture);
         boundaries = boundaries.insert(key, capture);
       }