Fixes #92: implements frontmatter syntax

common/deps.ts

@@ -27,6 +27,7 @@ export type {
   BlockContext,
   LeafBlock,
   LeafBlockParser,
+  Line,
   MarkdownConfig,
   MarkdownExtension,
 } from "@lezer/markdown";

common/parse_tree.ts

@@ -2,6 +2,7 @@ import { ParseTree } from "$sb/lib/tree.ts";
 
 import type { SyntaxNode } from "./deps.ts";
 import type { Language } from "./deps.ts";
+
 export function lezerToParseTree(
   text: string,
   n: SyntaxNode,
@@ -24,10 +25,10 @@ export function lezerToParseTree(
       },
     ];
   } else {
-    let newChildren: ParseTree[] = [];
+    const newChildren: ParseTree[] = [];
     let index = n.from;
-    for (let child of children) {
-      let s = text.substring(index, child.from);
+    for (const child of children) {
+      const s = text.substring(index, child.from);
       if (s) {
         newChildren.push({
           from: index + offset,
@@ -38,14 +39,14 @@ export function lezerToParseTree(
       newChildren.push(child);
       index = child.to!;
     }
-    let s = text.substring(index, n.to);
+    const s = text.substring(index, n.to);
     if (s) {
       newChildren.push({ from: index + offset, to: n.to + offset, text: s });
     }
     children = newChildren;
   }
 
-  let result: ParseTree = {
+  const result: ParseTree = {
     type: n.name,
     from: n.from + offset,
     to: n.to + offset,
@@ -60,7 +61,7 @@ export function lezerToParseTree(
 }
 
 export function parse(language: Language, text: string): ParseTree {
-  let tree = lezerToParseTree(text, language.parser.parse(text).topNode);
+  const tree = lezerToParseTree(text, language.parser.parse(text).topNode);
   // replaceNodesMatching(tree, (n): MarkdownTree | undefined | null => {
   //   if (n.type === "FencedCode") {
   //     let infoN = findNodeMatching(n, (n) => n.type === "CodeInfo");

common/parser.test.ts

@@ -0,0 +1,38 @@
+import { parse } from "./parse_tree.ts";
+import buildMarkdown from "./parser.ts";
+import { findNodeOfType, renderToText } from "../plug-api/lib/tree.ts";
+import { assertEquals, assertNotEquals } from "../test_deps.ts";
+
+const sample1 = `---
+type: page
+tags:
+- hello
+- world
+
+---
+# This is a doc
+
+Supper`;
+
+const sampleInvalid1 = `---
+name: Zef
+# This is a doc
+
+Supper`;
+
+Deno.test("Test parser", () => {
+  const lang = buildMarkdown([]);
+  let tree = parse(
+    lang,
+    sample1,
+  );
+  // Check if rendering back to text works
+  assertEquals(renderToText(tree), sample1);
+  // console.log("tree", JSON.stringify(tree, null, 2));
+  let node = findNodeOfType(tree, "FrontMatter");
+  assertNotEquals(node, undefined);
+  tree = parse(lang, sampleInvalid1);
+  node = findNodeOfType(tree, "FrontMatter");
+  // console.log("Invalid node", node);
+  assertEquals(node, undefined);
+});

common/parser.ts

@@ -1,17 +1,17 @@
 import {
   BlockContext,
   Language,
-  LanguageDescription,
-  LanguageSupport,
   LeafBlock,
   LeafBlockParser,
+  Line,
   markdown,
   MarkdownConfig,
-  parseCode,
+  StreamLanguage,
   styleTags,
   Table,
   tags as t,
   TaskList,
+  yamlLanguage,
 } from "./deps.ts";
 import * as ct from "./customtags.ts";
 import {
@@ -92,7 +92,7 @@ export const Comment: MarkdownConfig = {
   parseBlock: [
     {
       name: "Comment",
-      leaf(cx, leaf) {
+      leaf(_cx, leaf) {
         return /^%%\s/.test(leaf.content) ? new CommentParser() : null;
       },
       after: "SetextHeading",
@@ -100,34 +100,80 @@ export const Comment: MarkdownConfig = {
   ],
 };
 
+// FrontMatter parser
+
+const lang = StreamLanguage.define(yamlLanguage);
+
+export const FrontMatter: MarkdownConfig = {
+  defineNodes: [
+    { name: "FrontMatter", block: true },
+    { name: "FrontMatterMarker" },
+    { name: "FrontMatterCode" },
+  ],
+  parseBlock: [{
+    name: "FrontMatter",
+    parse: (cx, line: Line) => {
+      if (cx.parsedPos !== 0) {
+        return false;
+      }
+      if (line.text !== "---") {
+        return false;
+      }
+      const frontStart = cx.parsedPos;
+      const elts = [
+        cx.elt(
+          "FrontMatterMarker",
+          cx.parsedPos,
+          cx.parsedPos + line.text.length + 1,
+        ),
+      ];
+      cx.nextLine();
+      const startPos = cx.parsedPos;
+      let endPos = startPos;
+      let text = "";
+      let lastPos = cx.parsedPos;
+      do {
+        text += line.text + "\n";
+        endPos += line.text.length + 1;
+        cx.nextLine();
+        if (cx.parsedPos === lastPos) {
+          // End of file, no progress made, there may be a better way to do this but :shrug:
+          return false;
+        }
+        lastPos = cx.parsedPos;
+      } while (line.text !== "---");
+      const yamlTree = lang.parser.parse(text);
+
+      elts.push(
+        cx.elt("FrontMatterCode", startPos, endPos, [
+          cx.elt(yamlTree, startPos),
+        ]),
+      );
+      endPos = cx.parsedPos + line.text.length;
+      elts.push(cx.elt(
+        "FrontMatterMarker",
+        cx.parsedPos,
+        cx.parsedPos + line.text.length,
+      ));
+      cx.nextLine();
+      cx.addElement(cx.elt("FrontMatter", frontStart, endPos, elts));
+      return true;
+    },
+    before: "HorizontalRule",
+  }],
+};
+
 export default function buildMarkdown(mdExtensions: MDExt[]): Language {
   return markdown({
     extensions: [
       WikiLink,
+      FrontMatter,
       TaskList,
       Comment,
       Strikethrough,
       Table,
       ...mdExtensions.map(mdExtensionSyntaxConfig),
-      // parseCode({
-      //   codeParser: getCodeParser([
-      //     LanguageDescription.of({
-      //       name: "yaml",
-      //       alias: ["meta", "data"],
-      //       support: new LanguageSupport(StreamLanguage.define(yaml)),
-      //     }),
-      //     LanguageDescription.of({
-      //       name: "javascript",
-      //       alias: ["js"],
-      //       support: new LanguageSupport(javascriptLanguage),
-      //     }),
-      //     LanguageDescription.of({
-      //       name: "typescript",
-      //       alias: ["ts"],
-      //       support: new LanguageSupport(typescriptLanguage),
-      //     }),
-      //   ]),
-      // }),
+
       {
         props: [
           styleTags({