From e5ddcadd3cca81b7ad52339bb0fa7e95c93340aa Mon Sep 17 00:00:00 2001
From: Marcin Gasperowicz <xnooga@gmail.com>
Date: Sun, 25 Oct 2020 14:46:51 +0100
Subject: [PATCH] LibJS: Parse line continuations in string literals properly

Newlines after line continuation were inserted into the string
literals. This patch makes the parser ignore the newlines after \ and
also makes it so that "use strict" containing a line continuation is
not a valid "use strict".
---
 Libraries/LibJS/Tests/functions/function-strict-mode.js | 6 ++++++
 Libraries/LibJS/Tests/template-literals.js              | 7 +++++++
 Libraries/LibJS/Tests/test-common-tests.js              | 3 +++
 Libraries/LibJS/Token.cpp                               | 2 ++
 4 files changed, 18 insertions(+)

diff --git a/Libraries/LibJS/Tests/functions/function-strict-mode.js b/Libraries/LibJS/Tests/functions/function-strict-mode.js
index 85f022603d..08145bf089 100644
--- a/Libraries/LibJS/Tests/functions/function-strict-mode.js
+++ b/Libraries/LibJS/Tests/functions/function-strict-mode.js
@@ -30,6 +30,12 @@ test("use strict with double quotes after statement does not yield strict mode c
     expect(isStrictMode()).toBeFalse();
 });
 
+test("use strict interrupted by a line continuation does not yield strict mode code", () => {
+    "use \
+    strict";
+    expect(isStrictMode()).toBeFalse();
+});
+
 test("strict mode propagates down the scope chain", () => {
     "use strict";
     expect(isStrictMode()).toBeTrue();
diff --git a/Libraries/LibJS/Tests/template-literals.js b/Libraries/LibJS/Tests/template-literals.js
index 17cb548641..07d81509a8 100644
--- a/Libraries/LibJS/Tests/template-literals.js
+++ b/Libraries/LibJS/Tests/template-literals.js
@@ -53,6 +53,13 @@ test("newline literals (not characters)", () => {
     ).toBe("foo\n    bar");
 });
 
+test("line continuation in literals (not characters)", () => {
+    expect(
+        `foo\
+    bar`
+    ).toBe("foo    bar");
+});
+
 test("reference error from expressions", () => {
     expect(() => `${b}`).toThrowWithMessage(ReferenceError, "'b' is not defined");
 });
diff --git a/Libraries/LibJS/Tests/test-common-tests.js b/Libraries/LibJS/Tests/test-common-tests.js
index 31951fffde..a2071f15a0 100644
--- a/Libraries/LibJS/Tests/test-common-tests.js
+++ b/Libraries/LibJS/Tests/test-common-tests.js
@@ -53,6 +53,9 @@ test("toHaveLength", () => {
     expect([1]).toHaveLength(1);
     expect({ length: 1 }).toHaveLength(1);
 
+    expect("a\
+b").toHaveLength(2);
+
     expect(() => {
         expect(1).toHaveLength();
     }).toThrow(ExpectationError);
diff --git a/Libraries/LibJS/Token.cpp b/Libraries/LibJS/Token.cpp
index 57190ef487..89a3b212ac 100644
--- a/Libraries/LibJS/Token.cpp
+++ b/Libraries/LibJS/Token.cpp
@@ -155,6 +155,8 @@ String Token::string_value(StringValueStatus& status) const
             case '\\':
                 builder.append('\\');
                 break;
+            case '\n':
+                break;
             case 'x': {
                 if (i + 2 >= m_value.length() - offset)
                     return encoding_failure(StringValueStatus::MalformedHexEscape);