Fix: Correctly escape newlines in constructType function (#5955)

* Fix: Escape newlines in multi-line strings for `wrangler types` generation

* Add test for handling multiline strings in `constructType` function

* Add changeset for newline escape fix in constructType function

* fix: Simplify `constructType` function by using JSON.stringify for value escaping

* Update packages/wrangler/src/type-generation.ts

Remove unnecessary quotation marks around JSON.stringify output

Co-authored-by: Somhairle MacLeòid <[email protected]>

* fix changeset formatting

* fix type-gen escaping tests

---------

Co-authored-by: Somhairle MacLeòid <[email protected]>
Co-authored-by: Peter Bacon Darwin <[email protected]>

.changeset/shy-planets-move.md

@@ -0,0 +1,7 @@
+---
+"wrangler": patch
+---
+
+fix: correctly escape newlines in `constructType` function for multiline strings
+
+This fix ensures that multiline strings are correctly handled by the `constructType` function. Newlines are now properly escaped to prevent invalid JavaScript code generation when using the `wrangler types` command. This improves robustness and prevents errors related to multiline string handling in environment variables and other configuration settings.

packages/wrangler/src/__tests__/type-generation.test.ts

@@ -65,9 +65,9 @@ describe("constructType", () => {
 		);
 
 		expect(constructType("valid", 'a"', false)).toBe('valid: "a\\"";');
-		expect(constructType("valid", "a\\", false)).toBe('valid: "a\\";');
-		expect(constructType("valid", "a\\b", false)).toBe('valid: "a\\b";');
-		expect(constructType("valid", 'a\\b"', false)).toBe('valid: "a\\b\\"";');
+		expect(constructType("valid", "a\\", false)).toBe('valid: "a\\\\";');
+		expect(constructType("valid", "a\\b", false)).toBe('valid: "a\\\\b";');
+		expect(constructType("valid", 'a\\b"', false)).toBe('valid: "a\\\\b\\"";');
 
 		expect(constructType("valid", 1)).toBe("valid: 1;");
 		expect(constructType("valid", 12345)).toBe("valid: 12345;");
@@ -76,6 +76,14 @@ describe("constructType", () => {
 	});
 });
 
+describe("constructType with multiline strings", () => {
+	it("should correctly escape newlines in string values", () => {
+		const multilineString = "This is a\nmulti-line\nstring";
+		const expected = `valid: "This is a\\nmulti-line\\nstring";`;
+		expect(constructType("valid", multilineString, false)).toBe(expected);
+	});
+});
+
 const bindingsConfigMock: Omit<
 	EnvironmentNonInheritable,
 	"define" | "tail_consumers" | "constellation" | "cloudchamber"

packages/wrangler/src/type-generation.ts

@@ -144,7 +144,7 @@ export function constructType(
 		if (useRawVal) {
 			return `${typeKey}: ${value};`;
 		}
-		return `${typeKey}: "${value.replace(/"/g, '\\"')}";`;
+		return `${typeKey}: ${JSON.stringify(value)};`;
 	}
 	if (typeof value === "number" || typeof value === "boolean") {
 		return `${typeKey}: ${value};`;