From 1afd5cf7e99bf9937ff10de8b276bdcbfc3280c6 Mon Sep 17 00:00:00 2001
From: Joshua Lochner <admin@xenova.com>
Date: Fri, 15 Dec 2023 02:22:39 +0200
Subject: [PATCH] [`@huggingface/jinja`] Fix escaped characters (#416)

Better parsing of escaped newlines, tabs, etc. Also adds a unit test for this.
---
 packages/jinja/src/lexer.ts           | 29 +++++++++++++++++++++++
 packages/jinja/src/runtime.ts         |  7 +-----
 packages/jinja/test/templates.test.js | 33 +++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 6 deletions(-)

diff --git a/packages/jinja/src/lexer.ts b/packages/jinja/src/lexer.ts
index 1e6015164..3dd6eaafb 100644
--- a/packages/jinja/src/lexer.ts
+++ b/packages/jinja/src/lexer.ts
@@ -123,6 +123,18 @@ const ORDERED_MAPPING_TABLE: [string, TokenType][] = [
 	["=", TOKEN_TYPES.Equals],
 ];
 
+const ESCAPE_CHARACTERS = new Map([
+	["n", "\n"], // New line
+	["t", "\t"], // Horizontal tab
+	["r", "\r"], // Carriage return
+	["b", "\b"], // Backspace
+	["f", "\f"], // Form feed
+	["v", "\v"], // Vertical tab
+	["'", "'"], // Single quote
+	['"', '"'], // Double quote
+	["\\", "\\"], // Backslash
+]);
+
 /**
  * Generate a list of tokens from a source string.
  */
@@ -135,6 +147,23 @@ export function tokenize(source: string): Token[] {
 	const consumeWhile = (predicate: (char: string) => boolean): string => {
 		let str = "";
 		while (predicate(src[cursorPosition])) {
+			// Check for escaped characters
+			if (src[cursorPosition] === "\\") {
+				// Consume the backslash
+				++cursorPosition;
+				// Check for end of input
+				if (cursorPosition >= src.length) throw new SyntaxError("Unexpected end of input");
+
+				// Add the escaped character
+				const escaped = src[cursorPosition++];
+				const unescaped = ESCAPE_CHARACTERS.get(escaped);
+				if (unescaped === undefined) {
+					throw new SyntaxError(`Unexpected escaped character: ${escaped}`);
+				}
+				str += unescaped;
+				continue;
+			}
+
 			str += src[cursorPosition++];
 			if (cursorPosition >= src.length) throw new SyntaxError("Unexpected end of input");
 		}
diff --git a/packages/jinja/src/runtime.ts b/packages/jinja/src/runtime.ts
index da02dffee..ec44705ef 100644
--- a/packages/jinja/src/runtime.ts
+++ b/packages/jinja/src/runtime.ts
@@ -486,12 +486,7 @@ export class Interpreter {
 			case "NumericLiteral":
 				return new NumericValue(Number((statement as NumericLiteral).value));
 			case "StringLiteral":
-				return new StringValue(
-					(statement as StringLiteral).value
-						// Unescape special characters
-						.replaceAll("\\n", "\n")
-						.replaceAll("\\t", "\t")
-				);
+				return new StringValue((statement as StringLiteral).value);
 			case "BooleanLiteral":
 				return new BooleanValue((statement as BooleanLiteral).value);
 			case "Identifier":
diff --git a/packages/jinja/test/templates.test.js b/packages/jinja/test/templates.test.js
index 1525cd98c..10e4d2f1b 100644
--- a/packages/jinja/test/templates.test.js
+++ b/packages/jinja/test/templates.test.js
@@ -60,6 +60,9 @@ const TEST_STRINGS = {
 	MEMBERSHIP: `|{{ 0 in arr }}|{{ 1 in arr }}|{{ true in arr }}|{{ false in arr }}|{{ 'a' in arr }}|{{ 'b' in arr }}|`,
 	MEMBERSHIP_NEGATION_1: `|{{ not 0 in arr }}|{{ not 1 in arr }}|{{ not true in arr }}|{{ not false in arr }}|{{ not 'a' in arr }}|{{ not 'b' in arr }}|`,
 	MEMBERSHIP_NEGATION_2: `|{{ 0 not in arr }}|{{ 1 not in arr }}|{{ true not in arr }}|{{ false not in arr }}|{{ 'a' not in arr }}|{{ 'b' not in arr }}|`,
+
+	// Escaped characters
+	ESCAPED_CHARS: `{{ '\\n' }}{{ '\\t' }}{{ '\\'' }}{{ '\\"' }}{{ '\\\\' }}{{ '|\\n|\\t|\\'|\\"|\\\\|' }}`,
 };
 
 const TEST_PARSED = {
@@ -1019,6 +1022,28 @@ const TEST_PARSED = {
 		{ value: "}}", type: "CloseExpression" },
 		{ value: "|", type: "Text" },
 	],
+
+	// Escaped characters
+	ESCAPED_CHARS: [
+		{ value: "{{", type: "OpenExpression" },
+		{ value: "\n", type: "StringLiteral" },
+		{ value: "}}", type: "CloseExpression" },
+		{ value: "{{", type: "OpenExpression" },
+		{ value: "\t", type: "StringLiteral" },
+		{ value: "}}", type: "CloseExpression" },
+		{ value: "{{", type: "OpenExpression" },
+		{ value: "'", type: "StringLiteral" },
+		{ value: "}}", type: "CloseExpression" },
+		{ value: "{{", type: "OpenExpression" },
+		{ value: '"', type: "StringLiteral" },
+		{ value: "}}", type: "CloseExpression" },
+		{ value: "{{", type: "OpenExpression" },
+		{ value: "\\", type: "StringLiteral" },
+		{ value: "}}", type: "CloseExpression" },
+		{ value: "{{", type: "OpenExpression" },
+		{ value: `|\n|\t|'|"|\\|`, type: "StringLiteral" },
+		{ value: "}}", type: "CloseExpression" },
+	],
 };
 
 const TEST_CONTEXT = {
@@ -1115,6 +1140,9 @@ const TEST_CONTEXT = {
 	MEMBERSHIP_NEGATION_2: {
 		arr: [0, true, "a"],
 	},
+
+	// Escaped characters
+	ESCAPED_CHARS: {},
 };
 
 const EXPECTED_OUTPUTS = {
@@ -1173,6 +1201,11 @@ const EXPECTED_OUTPUTS = {
 	MEMBERSHIP: "|true|false|true|false|true|false|",
 	MEMBERSHIP_NEGATION_1: "|false|true|false|true|false|true|",
 	MEMBERSHIP_NEGATION_2: "|false|true|false|true|false|true|",
+
+	// Escaped characters
+	// NOTE: Since `trim_blocks` is enabled, we remove the first newline after the template tag,
+	// meaning the first newline in the output is not present
+	ESCAPED_CHARS: `\t'"\\|\n|\t|'|"|\\|`,
 };
 
 describe("Templates", () => {