phase 12: tags — lexer, AST, index, anchor resolution, ws/symbol

Vimwiki `:tag1:tag2:` syntax across the full stack. P11 resolved as
strict-vimwiki — no markdown `#tag` alias.

AST (nuwiki-core):
- `TagScope { File, Heading(usize), Standalone }` mirrors vimwiki's
  three placement-determined meanings: lines 0-1 → File; one or two
  lines below the most recent heading → Heading(idx); otherwise
  Standalone.
- `TagNode { span, tags: Vec<String>, scope }` + `BlockNode::Tag`.
- `PageMetadata.tags: Vec<String>` accumulates the file-scope tag
  names — convenience projection of the Tag blocks whose scope is
  File. New field is additive (Default derive) so existing consumers
  using `..Default::default()` keep working.
- `Visitor::visit_tag` lands with a default body and `walk_block`
  dispatches the new arm.

Lexer (`syntax/vimwiki/lexer.rs`):
- `VimwikiTokenKind::Tag(Vec<String>)` block-level token.
- `try_lex_tag` runs in the normal-line dispatcher right after heading
  recognition; demands the *whole trimmed line* match `:name:name…:`,
  with non-empty whitespace-free names between adjacent colons. Empty
  segments (`::tag::`), whitespace inside a name, or single-colon
  lines are all rejected. Doesn't fight `Term::` (definition-list
  marker) because that pattern requires text before the `::`.
- Indentation is tolerated; the span covers the trimmed run.

Parser (`syntax/vimwiki/parser.rs`):
- `ParseState` gains `headings_seen` + `last_heading_line`.
- `parse_heading` bumps both on every closed heading so the tag
  parser can detect the heading window.
- `parse_tag` reads the Tag token, computes the scope via
  `scope_for_tag(tag_line)`, eats the trailing newline, and emits the
  TagNode.
- `parse_document` post-processes each block: when a Tag with
  `scope == File` is emitted, its names are pushed (de-duped) into
  `metadata.tags`.

Renderer (`render/html.rs`):
- `render_tag` emits `<div class="tags"><span class="tag"
  id="tag-name">name</span>...</div>`. The `id` is what makes
  `[[Page#tag-name]]` jump to the rendered tag.

Semantic tokens (`semantic_tokens.rs`):
- New `TOKEN_TAG = 19` / `vimwikiTag` so editors highlight tag lines
  distinctly. `emit_block` adds the Tag arm.

Workspace index (`index.rs`):
- `IndexedPage.tags: Vec<TagInfo>` records each tag occurrence on a
  page with its span + scope.
- `WorkspaceIndex.tags_by_name: HashMap<String, Vec<TagOccurrence>>`
  is the reverse map for cross-page anchor resolution + the Phase 13
  `nuwiki.tags.search` command.
- `upsert` populates both; `remove` scrubs the reverse map and drops
  empty entries; `tags_for(name)` is the public lookup.

LSP handlers (`lib.rs`):
- `heading_range_in` falls back to tag matching when the anchor
  isn't a heading slug — so `[[Page#some-tag]]` lands on the matching
  TagNode. Heading anchors win over tag anchors when both match (the
  vimwiki precedence).
- `workspace/symbol` includes tags alongside headings, named `:tag:`
  and kinded `PROPERTY` so editor UIs can distinguish them.

Tests (20 new):
- Syntax (15 in `vimwiki_tags.rs`):
  lexer recognition + rejection of `::tag::`, whitespace-in-name,
  Term::-conflict; parser scope paths (file, heading-1-below,
  heading-2-below, standalone, no-heading, line-1 priority);
  metadata dedup; renderer HTML + escaping.
- LSP index (5 in `tags_index_and_lsp.rs`):
  per-page tag population, cross-page `tags_by_name` aggregation,
  re-upsert replaces stale tags, `remove` cleans the reverse map,
  heading-scope tag indexed but not in file metadata.

All 191 v1.0 + Phase 11 tests still pass — backward compatible.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/nuwiki-lsp/src/index.rs

@@ -15,7 +15,7 @@ use std::path::{Path, PathBuf};
 
 use nuwiki_core::ast::{
     BlockNode, BlockquoteNode, DocumentNode, InlineNode, LinkKind, LinkTarget, ListNode, Span,
-    TableNode,
+    TableNode, TagScope,
 };
 use tower_lsp::lsp_types::Url;
 
@@ -28,6 +28,19 @@ pub struct IndexedPage {
     pub title: Option<String>,
     pub headings: Vec<HeadingInfo>,
     pub outgoing: Vec<OutgoingLink>,
+    /// Phase 12: every `TagNode` on the page. `tags_by_name` on the
+    /// containing `WorkspaceIndex` is the reverse map.
+    pub tags: Vec<TagInfo>,
+}
+
+/// One tag occurrence on a page. `name` is the bare tag string (no
+/// surrounding colons). Multiple tags on the same source line each get
+/// their own `TagInfo` so anchor lookup can return a precise location.
+#[derive(Debug, Clone)]
+pub struct TagInfo {
+    pub name: String,
+    pub scope: TagScope,
+    pub span: Span,
 }
 
 #[derive(Debug, Clone)]
@@ -56,12 +69,25 @@ pub struct Backlink {
     pub target_anchor: Option<String>,
 }
 
+/// A tag's location, used by `WorkspaceIndex::tags_for` for cross-page
+/// `[[Page#tag]]` resolution and `nuwiki.tags.search` (Phase 13).
+#[derive(Debug, Clone)]
+pub struct TagOccurrence {
+    pub uri: Url,
+    pub span: Span,
+    pub scope: TagScope,
+}
+
 #[derive(Debug, Default)]
 pub struct WorkspaceIndex {
     pub root: Option<PathBuf>,
     pub pages_by_uri: HashMap<Url, IndexedPage>,
     pub pages_by_name: HashMap<String, Url>,
     pub backlinks: HashMap<String, Vec<Backlink>>,
+    /// Phase 12: tag name → every occurrence across the workspace. Used by
+    /// the v1.1 nav handlers (tag-as-anchor `definition`, `workspace/symbol`
+    /// inclusion) and the Phase 13 `nuwiki.tags.search` command.
+    pub tags_by_name: HashMap<String, Vec<TagOccurrence>>,
 }
 
 impl WorkspaceIndex {
@@ -84,6 +110,7 @@ impl WorkspaceIndex {
             title: ast.metadata.title.clone(),
             headings: Vec::new(),
             outgoing: Vec::new(),
+            tags: Vec::new(),
         };
         index_blocks(&ast.children, &mut page);
 
@@ -100,6 +127,18 @@ impl WorkspaceIndex {
             }
         }
 
+        // Phase 12: maintain the reverse tag map alongside the per-page list.
+        for tag in &page.tags {
+            self.tags_by_name
+                .entry(tag.name.clone())
+                .or_default()
+                .push(TagOccurrence {
+                    uri: uri.clone(),
+                    span: tag.span,
+                    scope: tag.scope,
+                });
+        }
+
         self.pages_by_name.insert(name, uri.clone());
         self.pages_by_uri.insert(uri, page);
     }
@@ -112,6 +151,19 @@ impl WorkspaceIndex {
             entries.retain(|b| &b.source_uri != uri);
         }
         self.backlinks.retain(|_, v| !v.is_empty());
+        for entries in self.tags_by_name.values_mut() {
+            entries.retain(|t| &t.uri != uri);
+        }
+        self.tags_by_name.retain(|_, v| !v.is_empty());
+    }
+
+    /// All occurrences of a tag across the workspace. Empty slice when the
+    /// tag isn't indexed.
+    pub fn tags_for(&self, name: &str) -> &[TagOccurrence] {
+        self.tags_by_name
+            .get(name)
+            .map(Vec::as_slice)
+            .unwrap_or(&[])
     }
 
     /// Resolve a `LinkTarget` to a page URI in this workspace.
@@ -258,6 +310,15 @@ fn index_block(block: &BlockNode, page: &mut IndexedPage) {
                 }
             }
         }
+        BlockNode::Tag(t) => {
+            for name in &t.tags {
+                page.tags.push(TagInfo {
+                    name: name.clone(),
+                    scope: t.scope,
+                    span: t.span,
+                });
+            }
+        }
         _ => {}
     }
 }

crates/nuwiki-lsp/src/lib.rs

@@ -622,6 +622,24 @@ impl LanguageServer for Backend {
                         });
                     }
                 }
+                // Phase 12: surface tags too, named as `:tag:` so editors
+                // can distinguish them from headings at a glance.
+                for t in &page.tags {
+                    if q.is_empty() || t.name.to_lowercase().contains(&q) {
+                        #[allow(deprecated)]
+                        out.push(LspSymbolInformation {
+                            name: format!(":{}:", t.name),
+                            kind: SymbolKind::PROPERTY,
+                            tags: None,
+                            deprecated: None,
+                            location: Location {
+                                uri: page.uri.clone(),
+                                range: span_to_lsp_range_no_text(&t.span),
+                            },
+                            container_name: Some(page.name.clone()),
+                        });
+                    }
+                }
             }
         }
         Ok(Some(out))
@@ -964,8 +982,15 @@ fn zero_range() -> Range {
 
 fn heading_range_in(idx: &WorkspaceIndex, uri: &Url, anchor: &str, _utf8: bool) -> Option<Range> {
     let page = idx.page(uri)?;
-    let h = page.headings.iter().find(|h| h.anchor == anchor)?;
-    Some(span_to_lsp_range_no_text(&h.span))
+    // Headings win over tags when both match — same precedence as
+    // vimwiki: heading anchors are the "canonical" target shape.
+    if let Some(h) = page.headings.iter().find(|h| h.anchor == anchor) {
+        return Some(span_to_lsp_range_no_text(&h.span));
+    }
+    // Phase 12: tags-as-anchors. `[[Page#tag-name]]` lands on the
+    // matching `TagNode` on the target page.
+    let t = page.tags.iter().find(|t| t.name == anchor)?;
+    Some(span_to_lsp_range_no_text(&t.span))
 }
 
 fn is_inside_wikilink(text: &str, line: u32, byte_col: u32) -> bool {

crates/nuwiki-lsp/src/semantic_tokens.rs

@@ -46,6 +46,7 @@ pub const TOKEN_TRANSCLUSION: u32 = 15;
 pub const TOKEN_URL: u32 = 16;
 pub const TOKEN_COMMENT: u32 = 17;
 pub const TOKEN_DEFINITION_TERM: u32 = 18;
+pub const TOKEN_TAG: u32 = 19;
 
 pub const TOKEN_TYPE_NAMES: &[&str] = &[
     "vimwikiHeading",
@@ -67,6 +68,7 @@ pub const TOKEN_TYPE_NAMES: &[&str] = &[
     "vimwikiUrl",
     "vimwikiComment",
     "vimwikiDefinitionTerm",
+    "vimwikiTag",
 ];
 
 pub const MOD_LEVEL1: u32 = 1 << 0;
@@ -197,6 +199,7 @@ fn emit_block(block: &BlockNode, text: &str, idx: &LineIndex, out: &mut Vec<RawT
             }
         }
         BlockNode::Comment(c) => split_span(c.span, text, idx, TOKEN_COMMENT, 0, out),
+        BlockNode::Tag(t) => split_span(t.span, text, idx, TOKEN_TAG, 0, out),
         BlockNode::Error(_) => {}
     }
 }

crates/nuwiki-lsp/tests/tags_index_and_lsp.rs

@@ -0,0 +1,84 @@
+//! Phase 12 LSP-side tag tests:
+//! - WorkspaceIndex maintains per-page tag lists and a reverse map.
+//! - `tags_for` returns occurrences across pages.
+//! - `upsert` replaces stale tags on re-parse.
+//! - `remove` drops the page's tags + cleans `tags_by_name`.
+
+use std::path::PathBuf;
+
+use nuwiki_core::syntax::vimwiki::VimwikiSyntax;
+use nuwiki_core::syntax::SyntaxPlugin;
+use nuwiki_lsp::index::WorkspaceIndex;
+use tower_lsp::lsp_types::Url;
+
+fn parse(src: &str) -> nuwiki_core::ast::DocumentNode {
+    VimwikiSyntax::new().parse(src)
+}
+
+#[test]
+fn upsert_populates_per_page_tags() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let uri = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    idx.upsert(uri.clone(), &parse(":alpha:beta:\n= Home =\n"));
+
+    let page = idx.page(&uri).expect("indexed");
+    assert_eq!(page.tags.len(), 2);
+    let names: Vec<_> = page.tags.iter().map(|t| t.name.as_str()).collect();
+    assert!(names.contains(&"alpha"));
+    assert!(names.contains(&"beta"));
+}
+
+#[test]
+fn tags_by_name_aggregates_across_pages() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let home = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    let about = Url::from_file_path("/wiki/About.wiki").unwrap();
+    idx.upsert(home.clone(), &parse(":shared:\n"));
+    idx.upsert(about.clone(), &parse(":shared:other:\n"));
+
+    let shared = idx.tags_for("shared");
+    assert_eq!(shared.len(), 2);
+    let uris: Vec<&Url> = shared.iter().map(|o| &o.uri).collect();
+    assert!(uris.contains(&&home));
+    assert!(uris.contains(&&about));
+
+    assert_eq!(idx.tags_for("other").len(), 1);
+    assert!(idx.tags_for("nonexistent").is_empty());
+}
+
+#[test]
+fn re_upsert_replaces_stale_tags() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let uri = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    idx.upsert(uri.clone(), &parse(":old:\n"));
+    assert_eq!(idx.tags_for("old").len(), 1);
+
+    idx.upsert(uri.clone(), &parse(":new:\n"));
+    assert!(idx.tags_for("old").is_empty());
+    assert_eq!(idx.tags_for("new").len(), 1);
+}
+
+#[test]
+fn remove_drops_tags_and_reverse_entries() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let uri = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    idx.upsert(uri.clone(), &parse(":a:b:\n"));
+    idx.remove(&uri);
+
+    assert!(idx.page(&uri).is_none());
+    assert!(idx.tags_for("a").is_empty());
+    assert!(idx.tags_for("b").is_empty());
+}
+
+#[test]
+fn heading_scope_tag_indexed_but_not_in_metadata() {
+    // Tag at the third line below a heading is `Heading`-scoped; the
+    // metadata.tags accumulator only collects file-scope tags.
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let uri = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    let doc = parse("para\n\n\n= H =\n:scoped:\n");
+    idx.upsert(uri.clone(), &doc);
+
+    assert_eq!(idx.tags_for("scoped").len(), 1);
+    assert!(doc.metadata.tags.is_empty());
+}