Start on parser v4.

packages/js/core/dist/document.cjs

@@ -1 +1 @@
-"use strict";Object.defineProperties(exports,{__esModule:{value:!0},[Symbol.toStringTag]:{value:"Module"}});const s=require("./parser.cjs");function a(l,u=" "){let r=s.createLineData(null,u);const t={ended:!1,clone(){return a(l.clone(),u)},async next(){if(r.line=await l.next(),r.line===null)return!0;s.parseLine(r)},current(){return t},line(){var e;return(e=r.line)==null?void 0:e.slice(r.offsetHead)},head(){var e;return(e=r.line)==null?void 0:e.slice(r.offsetHead,r.offsetTail)},tail(){var e;return(e=r.line)==null?void 0:e.slice(r.offsetTail)},level(){return r.level},async content(e=-1,n=[]){var i;return e===-1&&(e=r.level+1),await t.next()||r.level<e?n:(n.push(((i=r.line)==null?void 0:i.slice(e))||""),t.content(e,n))},async seek(e,n=-1){return n===-1&&(n=r.level),await t.next()?!1:t.head()===e?t:r.level<n?!1:t.seek(e,n)}};return t}exports.useDocument=a;
+"use strict";Object.defineProperties(exports,{__esModule:{value:!0},[Symbol.toStringTag]:{value:"Module"}});const u=require("./parser.cjs");function s(l,a=" "){let r=u.createLineData(null,a);const t={ended:!1,clone(){return s(l.clone(),a)},async next(){if(r.line=await l.next(),r.line===null)return!0;u.parseLine(r)},current(){return t},line(){var e;return(e=r.line)==null?void 0:e.slice(r.offsetHead)},head(){var e;return(e=r.line)==null?void 0:e.slice(r.offsetHead,r.offsetTail)},tail(){var e;return(e=r.line)==null?void 0:e.slice(r.offsetTail)},level(){return r.level},async content(e=-1,n=[]){var i;return e===-1&&(e=r.level+1),await t.next()||r.level<e?n:(n.push(((i=r.line)==null?void 0:i.slice(e))||""),t.content(e,n))},match(e){return e===t.head()},async each(e){const n=t.line()!==void 0?t.level():-1;for(;!(await t.next()||t.level()<=n||await e()););},async seek(e,n=-1){return n===-1&&(n=r.level),await t.next()?!1:t.head()===e?t:r.level<n?!1:t.seek(e,n)}};return t}exports.useDocument=s;

packages/js/core/dist/document.js

@@ -1,10 +1,10 @@
 import { parseLine as f, createLineData as s } from "./parser.js";
-function d(l, i = " ") {
-  let r = s(null, i);
-  const t = {
+function c(l, a = " ") {
+  let r = s(null, a);
+  const n = {
     ended: !1,
     clone() {
-      return d(l.clone(), i);
+      return c(l.clone(), a);
     },
     async next() {
       if (r.line = await l.next(), r.line === null)
@@ -12,7 +12,7 @@ function d(l, i = " ") {
       f(r);
     },
     current() {
-      return t;
+      return n;
     },
     line() {
       var e;
@@ -29,16 +29,24 @@ function d(l, i = " ") {
     level() {
       return r.level;
     },
-    async content(e = -1, n = []) {
-      var u;
-      return e === -1 && (e = r.level + 1), await t.next() || r.level < e ? n : (n.push(((u = r.line) == null ? void 0 : u.slice(e)) || ""), t.content(e, n));
+    async content(e = -1, t = []) {
+      var i;
+      return e === -1 && (e = r.level + 1), await n.next() || r.level < e ? t : (t.push(((i = r.line) == null ? void 0 : i.slice(e)) || ""), n.content(e, t));
     },
-    async seek(e, n = -1) {
-      return n === -1 && (n = r.level), await t.next() ? !1 : t.head() === e ? t : r.level < n ? !1 : t.seek(e, n);
+    match(e) {
+      return e === n.head();
+    },
+    async each(e) {
+      const t = n.line() !== void 0 ? n.level() : -1;
+      for (; !(await n.next() || n.level() <= t || await e()); )
+        ;
+    },
+    async seek(e, t = -1) {
+      return t === -1 && (t = r.level), await n.next() ? !1 : n.head() === e ? n : r.level < t ? !1 : n.seek(e, t);
     }
   };
-  return t;
+  return n;
 }
 export {
-  d as useDocument
+  c as useDocument
 };

packages/js/core/src/document.ts

@@ -10,6 +10,9 @@ type Document = {
   head: () => string,
   tail: () => string,
   content: (contentLevel: number, lines: string[]) => Promise<string>,
+  match: (matchHead: string) => boolean,
+  each: (handler: Function) => void,
+  buildObject: (allowList: Array<string>, handler: Function) => object,
   seek: (matchHead: string, contentLevel: number) => Promise<Document|false>
 }
 
@@ -61,6 +64,42 @@ export function useDocument (reader: Reader, indent: string = ' '): Document {
       return document.content(contentLevel, lines)
     },
 
+    match(matchHead: string): boolean {
+      return matchHead === document.head()
+    },
+
+    async each(handler: Function) {
+      // Set startLevel to -1 if we haven't started parsing the document yet.
+      // Otherwise we'll break to early, as the default value for doc.level() is 0.
+      const startLevel = document.line() !== undefined ? document.level() : -1
+
+      while(true) {
+        if (await document.next()) break
+        if (document.level() <= startLevel) break
+        if (await handler()) break
+      }
+    },
+
+    async buildObject(allowList = [], valHandler?: () => any) {
+      if (!valHandler) valHandler = () => document.tail().trim()
+
+      const obj = {}
+      await document.each(async () => {
+        if (!document.head()) return
+        if (!allowList.length || allowList.includes(document.head())) {
+          obj[document.head()] = await valHandler()
+          return
+        }
+
+        // Parse unspecified text into an array of lines and save to #text key.
+        if (allowList && !allowList.includes(document.head()) && allowList.includes('#text')) {
+          obj['#text'] = [document.line(), ...await document.content(document.level())]
+          return
+        }
+      })
+      return obj
+    },
+
     async seek (matchHead: string, contentLevel = -1): Promise<Document|false> {
       if (contentLevel === -1) contentLevel = lineData.level