feat(parser): add openImpliesClose option to disable implicit HTML changes

src/Parser.events.spec.ts

@@ -301,6 +301,15 @@ describe("Events", () => {
             '<Page\n    title="Hello world"\n    actionBarVisible="false"/>',
             { xmlMode: true },
         ));
+
+    it("openImpliesClose=false: no implicit close via map", () =>
+        runTest("<p>first<p>second</p></p>", { openImpliesClose: false }));
+
+    it("openImpliesClose=false: no implicit p open before close", () =>
+        runTest("<div>text</p></div>", { openImpliesClose: false }));
+
+    it("openImpliesClose=false: no implicit br open before close", () =>
+        runTest("<div>text</br></div>", { openImpliesClose: false }));
 });
 
 describe("Helper", () => {

src/Parser.ts

@@ -17,7 +17,7 @@ const tableSectionTags = new Set(["thead", "tbody", "tfoot", "tr", "td", "th"]);
 const ddtTags = new Set(["dd", "dt"]);
 const rtpTags = new Set(["rt", "rp"]);
 
-const openImpliesClose = new Map<string, Set<string>>([
+const impliesCloseMap = new Map<string, Set<string>>([
     ["tr", new Set(["tr", "th", "td"])],
     ["th", new Set(["th", "td"])],
     ["td", new Set(["thead", "th", "td"])],
@@ -208,6 +208,18 @@ export interface ParserOptions {
      * Allows the default tokenizer to be overwritten.
      */
     Tokenizer?: typeof Tokenizer;
+
+    /**
+     * If set to `true`, the parser will implicitly open and close HTML tags
+     * according to the HTML5 spec (e.g. `<p>` will implicitly close another
+     * `<p>` that is still open, `</p>` will implicitly open `<p>` if none is
+     * open). Set to `false` to disable all implicit HTML changes, preserving
+     * the original document structure more closely.
+     *
+     * This option has no effect when `xmlMode` is `true`.
+     * @default !xmlMode
+     */
+    openImpliesClose?: boolean;
 }
 
 /**
@@ -280,6 +292,8 @@ export class Parser implements Callbacks {
     private readonly recognizeSelfClosing: boolean;
     /** We are parsing HTML. Inverse of the `xmlMode` option. */
     private readonly htmlMode: boolean;
+    /** Whether implicit open/close logic is active (requires HTML mode + openImpliesClose option). */
+    private readonly impliesCloseEnabled: boolean;
     private readonly tokenizer: Tokenizer;
 
     private readonly buffers: string[] = [];
@@ -295,6 +309,7 @@ export class Parser implements Callbacks {
     ) {
         this.cbs = cbs ?? {};
         this.htmlMode = !this.options.xmlMode;
+        this.impliesCloseEnabled = this.htmlMode && (options.openImpliesClose ?? this.htmlMode);
         this.lowerCaseTagNames = options.lowerCaseTags ?? this.htmlMode;
         this.lowerCaseAttributeNames =
             options.lowerCaseAttributeNames ?? this.htmlMode;
@@ -410,12 +425,12 @@ export class Parser implements Callbacks {
          * stays null so endOpenTag is a no-op, and closeCurrentTag can't
          * match "" on the stack.
          */
-        if (this.htmlMode && name === "form" && this.stack.includes("form")) {
+        if (this.impliesCloseEnabled && name === "form" && this.stack.includes("form")) {
             this.tagname = "";
             return;
         }
 
-        const impliesClose = this.htmlMode && openImpliesClose.get(name);
+        const impliesClose = this.impliesCloseEnabled && impliesCloseMap.get(name);
 
         if (impliesClose) {
             while (this.stack.length > 0 && impliesClose.has(this.stack[0])) {
@@ -481,12 +496,12 @@ export class Parser implements Callbacks {
                     this.popElement(true);
                 }
                 this.popElement(false);
-            } else if (this.htmlMode && name === "p") {
+            } else if (this.impliesCloseEnabled && name === "p") {
                 // Implicit open before close
                 this.emitOpenTag("p");
                 this.closeCurrentTag(true);
             }
-        } else if (this.htmlMode && name === "br") {
+        } else if (this.impliesCloseEnabled && name === "br") {
             // We can't use `emitOpenTag` for implicit open, as `br` would be implicitly closed.
             this.cbs.onopentagname?.("br");
             this.cbs.onopentag?.("br", {}, true);

src/__snapshots__/Parser.events.spec.ts.snap

@@ -5304,6 +5304,161 @@ exports[`Events > open-implies-close case of (non-br) void close tag in non-XML
 ]
 `;
 
+exports[`Events > openImpliesClose=false: no implicit br open before close 1`] = `
+[
+  {
+    "$event": "opentagname",
+    "data": [
+      "div",
+    ],
+    "endIndex": 4,
+    "startIndex": 0,
+  },
+  {
+    "$event": "opentag",
+    "data": [
+      "div",
+      {},
+      false,
+    ],
+    "endIndex": 4,
+    "startIndex": 0,
+  },
+  {
+    "$event": "text",
+    "data": [
+      "text",
+    ],
+    "endIndex": 8,
+    "startIndex": 5,
+  },
+  {
+    "$event": "closetag",
+    "data": [
+      "div",
+      false,
+    ],
+    "endIndex": 19,
+    "startIndex": 14,
+  },
+]
+`;
+
+exports[`Events > openImpliesClose=false: no implicit close via map 1`] = `
+[
+  {
+    "$event": "opentagname",
+    "data": [
+      "p",
+    ],
+    "endIndex": 2,
+    "startIndex": 0,
+  },
+  {
+    "$event": "opentag",
+    "data": [
+      "p",
+      {},
+      false,
+    ],
+    "endIndex": 2,
+    "startIndex": 0,
+  },
+  {
+    "$event": "text",
+    "data": [
+      "first",
+    ],
+    "endIndex": 7,
+    "startIndex": 3,
+  },
+  {
+    "$event": "opentagname",
+    "data": [
+      "p",
+    ],
+    "endIndex": 10,
+    "startIndex": 8,
+  },
+  {
+    "$event": "opentag",
+    "data": [
+      "p",
+      {},
+      false,
+    ],
+    "endIndex": 10,
+    "startIndex": 8,
+  },
+  {
+    "$event": "text",
+    "data": [
+      "second",
+    ],
+    "endIndex": 16,
+    "startIndex": 11,
+  },
+  {
+    "$event": "closetag",
+    "data": [
+      "p",
+      false,
+    ],
+    "endIndex": 20,
+    "startIndex": 17,
+  },
+  {
+    "$event": "closetag",
+    "data": [
+      "p",
+      false,
+    ],
+    "endIndex": 24,
+    "startIndex": 21,
+  },
+]
+`;
+
+exports[`Events > openImpliesClose=false: no implicit p open before close 1`] = `
+[
+  {
+    "$event": "opentagname",
+    "data": [
+      "div",
+    ],
+    "endIndex": 4,
+    "startIndex": 0,
+  },
+  {
+    "$event": "opentag",
+    "data": [
+      "div",
+      {},
+      false,
+    ],
+    "endIndex": 4,
+    "startIndex": 0,
+  },
+  {
+    "$event": "text",
+    "data": [
+      "text",
+    ],
+    "endIndex": 8,
+    "startIndex": 5,
+  },
+  {
+    "$event": "closetag",
+    "data": [
+      "div",
+      false,
+    ],
+    "endIndex": 18,
+    "startIndex": 13,
+  },
+]
+`;
+
 exports[`Events > plaintext 1`] = `
 [
   {