feat: Add multiline set functionality.

Author: pweglik

packages/jinja/src/ast.ts

@@ -51,7 +51,8 @@ export class SetStatement extends Statement {
 	override type = "Set";
 	constructor(
 		public assignee: Expression,
-		public value: Expression
+		public value: Expression | null, 
+		public body: Statement[]
 	) {
 		super();
 	}

packages/jinja/src/lexer.ts

@@ -39,6 +39,7 @@ export const TOKEN_TYPES = Object.freeze({
 	Is: "Is",
 	NotIn: "NotIn",
 	Else: "Else",
+	EndSet: "EndSet",
 	EndIf: "EndIf",
 	ElseIf: "ElseIf",
 	EndFor: "EndFor",
@@ -61,6 +62,7 @@ const KEYWORDS = Object.freeze({
 	is: TOKEN_TYPES.Is,
 	if: TOKEN_TYPES.If,
 	else: TOKEN_TYPES.Else,
+	endset: TOKEN_TYPES.EndSet,
 	endif: TOKEN_TYPES.EndIf,
 	elif: TOKEN_TYPES.ElseIf,
 	endfor: TOKEN_TYPES.EndFor,

packages/jinja/src/parser.ts

@@ -131,11 +131,27 @@ export function parse(tokens: Token[]): Program {
 
 		if (is(TOKEN_TYPES.Equals)) {
 			++current;
-			const value = parseSetStatement();
+			const value = parseExpression();
+
+			return new SetStatement(left, value, []);
+		} else {
+			// parsing multiline set here
+			const body: Statement[] = [];
+			expect(TOKEN_TYPES.CloseStatement, "Expected %} token");
+			while (
+				!(
+					tokens[current]?.type === TOKEN_TYPES.OpenStatement &&
+					tokens[current + 1]?.type === TOKEN_TYPES.EndSet
+				)
+			) {
+				const another = parseAny()
+				body.push(another);
+			}
+			expect(TOKEN_TYPES.OpenStatement, "Expected {% token");
+			expect(TOKEN_TYPES.EndSet, "Expected endset token");
 
-			return new SetStatement(left, value);
+			return new SetStatement(left, null, body);
 		}
-		return left;
 	}
 
 	function parseIfStatement(): If {

packages/jinja/src/runtime.ts

@@ -587,6 +587,8 @@ export class Interpreter {
 						);
 					case "join":
 						return new StringValue(operand.value.map((x) => x.value).join(""));
+					case "string":
+						return new StringValue(toJSON(operand));
 					default:
 						throw new Error(`Unknown ArrayValue filter: ${filter.value}`);
 				}
@@ -916,7 +918,7 @@ export class Interpreter {
 	}
 
 	private evaluateSet(node: SetStatement, environment: Environment): NullValue {
-		const rhs = this.evaluate(node.value, environment);
+		const rhs = node.value ? this.evaluate(node.value, environment) : this.evaluateBlock(node.body, environment);
 		if (node.assignee.type === "Identifier") {
 			const variableName = (node.assignee as Identifier).value;
 			environment.setVariable(variableName, rhs);