Add parsermode pragma

Fixes #7058

core/modules/parsers/wikiparser/rules/parsermode.js

@@ -0,0 +1,68 @@
+/*\
+title: $:/core/modules/parsers/wikiparser/rules/parsermode.js
+type: application/javascript
+module-type: wikirule
+
+Wiki pragma rule for parser mode specifications
+
+```
+\parsermode block
+\parsermode inline
+```
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+exports.name = "parsermode";
+exports.types = {pragma: true};
+
+/*
+Instantiate parse rule
+*/
+exports.init = function(parser) {
+	this.parser = parser;
+	// Regexp to match
+	this.matchRegExp = /^\\parsermode[^\S\n]/mg;
+};
+
+/*
+Parse the most recent match
+*/
+exports.parse = function() {
+	// Move past the pragma invocation
+	this.parser.pos = this.matchRegExp.lastIndex;
+	// Parse whitespace delimited tokens terminated by a line break
+	var reMatch = /[^\S\n]*(\S+)|(\r?\n)/mg,
+		parserMode = undefined;
+	reMatch.lastIndex = this.parser.pos;
+	var match = reMatch.exec(this.parser.source);
+	while(match && match.index === this.parser.pos) {
+		this.parser.pos = reMatch.lastIndex;
+		// Exit if we've got the line break
+		if(match[2]) {
+			break;
+		}
+		// Process the token
+		if(match[1]) {
+			parserMode = match[1];
+		}
+		// Match the next token
+		match = reMatch.exec(this.parser.source);
+	}
+	// Process the tokens
+	if(parserMode !== undefined) {
+		if(parserMode === "block") {
+			this.parser.parseAsInline = false;
+		} else if(parserMode === "inline") {
+			this.parser.parseAsInline = true;
+		}
+	}
+	// No parse tree nodes to return
+	return [];
+};
+
+})();