fix: add highlight support (#87)

Author: tylerdave

docs/Markdown Support.md

@@ -65,7 +65,7 @@ Rockgarden supports the superset of CommonMark, GFM (GitHub Flavored Markdown),
 
 | Feature       | Syntax             | Status | Notes                     |
 | ------------- | ------------------ | ------ | ------------------------- |
-| Highlights    | `==text==`         | ❌     | Future                    |
+| Highlights    | `==text==`         | ✅     | Renders as `<mark>`       |
 | Comments      | `%% comment %%`    | ❌     | Should strip during build |
 | HTML comments | `<!-- comment -->` | ✅     | Standard markdown         |
 
@@ -134,7 +134,6 @@ This ensures:
 
 ## Future Syntax Additions
 
-- Highlights: `==text==`
 - Comment stripping: `%% comment %%`
 - Block references: `[[page#^block]]`
 - Inline fields: `key:: value` (Dataview compatibility)

plans/tier-1-2-plan.md

@@ -9,7 +9,7 @@ One branch + PR per item. Plan → implement → test → PR → feedback → me
 - [x] 1a. Heading link fragments not slugified
 - [x] 1b. Macros not processed in transclusions
 - [x] 2a. Math rendering (KaTeX)
-- [ ] 2b. Highlights (`==text==`)
+- [x] 2b. Highlights (`==text==`)
 - [ ] 2c. Comment stripping (`%% comment %%`)
 - [ ] 3. Nav reverse ordering
 - [ ] 4. Dev server custom 404

src/rockgarden/obsidian/highlights.py

@@ -0,0 +1,111 @@
+"""Highlight syntax (==text==) for markdown-it-py.
+
+Ported from the JS markdown-it-mark plugin. Registers an inline rule that
+converts ==text== into <mark>text</mark>. Uses the delimiter runner pattern
+(same as emphasis/strikethrough).
+"""
+
+from markdown_it import MarkdownIt
+from markdown_it.rules_inline import StateInline
+from markdown_it.rules_inline.state_inline import Delimiter
+
+
+def highlight_plugin(md: MarkdownIt) -> None:
+    md.inline.ruler.before("emphasis", "mark", _mark_tokenize)
+    md.inline.ruler2.before("emphasis", "mark", _mark_post_process)
+    md.add_render_rule("mark_open", _mark_open)
+    md.add_render_rule("mark_close", _mark_close)
+
+
+def _mark_open(self, tokens, idx, options, env):
+    return "<mark>"
+
+
+def _mark_close(self, tokens, idx, options, env):
+    return "</mark>"
+
+
+def _mark_tokenize(state: StateInline, silent: bool) -> bool:
+    pos = state.pos
+    src = state.src
+
+    if src[pos] != "=":
+        return False
+
+    if silent:
+        return False
+
+    scanned = state.scanDelims(pos, True)
+    length = scanned.length
+
+    if length < 2:
+        return False
+
+    if length % 2:
+        token = state.push("text", "", 0)
+        token.content = "="
+        length -= 1
+
+    i = 0
+    while i < length:
+        token = state.push("text", "", 0)
+        token.content = "=="
+
+        state.delimiters.append(
+            Delimiter(
+                marker=ord("="),
+                length=0,
+                token=len(state.tokens) - 1,
+                end=-1,
+                open=scanned.can_open,
+                close=scanned.can_close,
+            )
+        )
+
+        i += 2
+
+    state.pos += scanned.length
+    return True
+
+
+def _mark_post_process(state: StateInline, *args) -> None:
+    delimiters = state.delimiters
+    lone_markers = []
+    maximum = len(delimiters)
+
+    i = maximum - 1
+    while i >= 0:
+        start_delim = delimiters[i]
+
+        if start_delim.marker != ord("="):
+            i -= 1
+            continue
+
+        if start_delim.end == -1:
+            i -= 1
+            continue
+
+        end_delim = delimiters[start_delim.end]
+
+        token = state.tokens[start_delim.token]
+        token.type = "mark_open"
+        token.tag = "mark"
+        token.nesting = 1
+        token.markup = "=="
+        token.content = ""
+
+        token = state.tokens[end_delim.token]
+        token.type = "mark_close"
+        token.tag = "mark"
+        token.nesting = -1
+        token.markup = "=="
+        token.content = ""
+
+        inner = state.tokens[end_delim.token - 1]
+        if inner.type == "text" and inner.content == "=":
+            lone_markers.append(end_delim.token - 1)
+
+        i -= 1
+
+    for idx in sorted(lone_markers, reverse=True):
+        del state.tokens[idx]

src/rockgarden/render/markdown.py

@@ -12,6 +12,8 @@
 from pygments.lexers import get_lexer_by_name
 from pygments.util import ClassNotFound
 
+from rockgarden.obsidian.highlights import highlight_plugin
+
 _md: MarkdownIt | None = None
 _highlight_formatter = HtmlFormatter(nowrap=False, cssclass="highlight")
 
@@ -50,6 +52,7 @@ def get_markdown_renderer() -> MarkdownIt:
     - Task lists (- [ ] item) via mdit-py-plugins
     - Footnotes ([^1] references and [^1]: definitions) via mdit-py-plugins
     - Dollar math ($..$ inline, $$...$$ block) via mdit-py-plugins
+    - Highlights (==text==) via custom plugin
     - Syntax highlighting via Pygments
     """
     global _md
@@ -58,6 +61,7 @@ def get_markdown_renderer() -> MarkdownIt:
         footnote_plugin(_md)
         tasklists_plugin(_md)
         dollarmath_plugin(_md, allow_digits=False, allow_space=False)
+        highlight_plugin(_md)
         _md.add_render_rule("fence", _fence_renderer)
     return _md
 

tests/test_highlights.py

@@ -0,0 +1,43 @@
+"""Tests for highlight (==text==) syntax."""
+
+from rockgarden.render.markdown import render_markdown
+
+
+class TestHighlights:
+    def test_basic_highlight(self):
+        result = render_markdown("This is ==highlighted== text")
+        assert "<mark>" in result
+        assert "highlighted" in result
+        assert "</mark>" in result
+
+    def test_highlight_with_inline_formatting(self):
+        result = render_markdown("==**bold highlight**==")
+        assert "<mark>" in result
+        assert "<strong>" in result
+
+    def test_multiple_highlights(self):
+        result = render_markdown("==one== and ==two==")
+        assert result.count("<mark>") == 2
+        assert result.count("</mark>") == 2
+
+    def test_no_empty_highlight(self):
+        result = render_markdown("====")
+        assert "<mark>" not in result
+
+    def test_highlight_in_code_block_unchanged(self):
+        result = render_markdown("```\n==not highlighted==\n```")
+        assert "<mark>" not in result
+
+    def test_inline_code_unchanged(self):
+        result = render_markdown("`==not highlighted==`")
+        assert "<mark>" not in result
+
+    def test_single_equals_not_highlight(self):
+        result = render_markdown("a = b")
+        assert "<mark>" not in result
+
+    def test_triple_equals_renders_with_extra_char(self):
+        """=== has an odd =, so it becomes = + ==highlight==."""
+        result = render_markdown("===highlighted===")
+        assert "<mark>" in result
+        assert "highlighted" in result