more relaxed boundary validation

only throw error when building multipart body bytes
show warning when parsing

src/Multipart.ts

@@ -59,14 +59,9 @@ export class Multipart implements Part {
      * @param parts The parts to include in the multipart
      * @param [boundary] The multipart boundary used to separate the parts. Randomly generated if not provided
      * @param [mediaType] The media type of the multipart. Defaults to "multipart/mixed"
-     *
-     * @throws {RangeError} If the boundary is invalid. A valid boundary is 1 to 70 characters long,
-     * does not end with space, and may only contain: A-Z a-z 0-9 '()+_,-./:=? and space
      */
     public constructor(public readonly parts: Part[], boundary: Uint8Array | string = crypto.randomUUID(), mediaType: string = "multipart/mixed") {
         this.#boundary = typeof boundary === "string" ? new TextEncoder().encode(boundary) : boundary;
-        if (!Multipart.isValidBoundary(this.#boundary))
-            throw new RangeError("Invalid boundary: must be 1 to 70 characters long, not end with space, and may only contain: A-Z a-z 0-9 '()+_,-./:=? and space");
         this.#mediaType = mediaType;
         this.setHeaders();
     }
@@ -121,13 +116,9 @@ export class Multipart implements Part {
 
     /**
      * Set the boundary bytes used to separate the parts
-     * @throws {RangeError} If the boundary is invalid. A valid boundary is 1 to 70 characters long,
-     * does not end with space, and may only contain: A-Z a-z 0-9 '()+_,-./:=? and space
      */
     public set boundary(boundary: Uint8Array | string) {
         this.#boundary = typeof boundary === "string" ? new TextEncoder().encode(boundary) : boundary;
-        if (!Multipart.isValidBoundary(this.#boundary))
-            throw new RangeError("Invalid boundary: must be 1 to 70 characters long, not end with space, and may only contain: A-Z a-z 0-9 '()+_,-./:=? and space");
         this.setHeaders();
     }
 
@@ -149,8 +140,14 @@ export class Multipart implements Part {
     /**
      * Get the bytes of the body of this multipart. Includes all parts separated by the boundary.
      * Does not include the headers.
+     *
+     * @throws {RangeError} If the multipart boundary is invalid. A valid boundary is 1 to 70 characters long,
+     * does not end with space, and may only contain: A-Z a-z 0-9 '()+_,-./:=? and space
      */
     public get body(): Uint8Array {
+        if (!Multipart.isValidBoundary(this.#boundary))
+            throw new RangeError("Invalid boundary: must be 1 to 70 characters long, not end with space, and may only contain: A-Z a-z 0-9 '()+_,-./:=? and space");
+
         const result: ArrayLike<number>[] = [];
         for (const part of this.parts) result.push(Multipart.DOUBLE_DASH, this.boundary, Multipart.CRLF, part.bytes(), Multipart.CRLF);
         result.push(Multipart.DOUBLE_DASH, this.boundary, Multipart.DOUBLE_DASH, Multipart.CRLF);
@@ -180,6 +177,9 @@ export class Multipart implements Part {
      * @param [mediaType] Multipart media type to pass to the constructor
      */
     public static parseBody(data: Uint8Array, boundary: Uint8Array, mediaType?: string): Multipart {
+        if (!Multipart.isValidBoundary(boundary))
+            console.warn("Invalid boundary:", new TextDecoder().decode(boundary), "\nMust be 1 to 70 characters long, not end with space, and may only contain: A-Z a-z 0-9 '()+_,-./:=? and space");
+
         const parts: Uint8Array[] = [];
         const fullBoundarySequence = new Uint8Array(Multipart.combineArrays([Multipart.DOUBLE_DASH, boundary, Multipart.CRLF]));
         const endBoundarySequence = new Uint8Array(Multipart.combineArrays([Multipart.DOUBLE_DASH, boundary, Multipart.DOUBLE_DASH, Multipart.CRLF]));
@@ -393,6 +393,9 @@ export class Multipart implements Part {
 
     /**
      * Get the bytes of the headers and {@link body} of this multipart.
+     *
+     * @throws {RangeError} If the multipart boundary is invalid. A valid boundary is 1 to 70 characters long,
+     * does not end with space, and may only contain: A-Z a-z 0-9 '()+_,-./:=? and space
      */
     public bytes(): Uint8Array {
         const result: ArrayLike<number>[] = [];

test/Multipart.test.js

@@ -27,30 +27,6 @@ describe("Multipart", function () {
             expect(new TextDecoder().decode(multipart.boundary)).to.equal("empty-boundary");
             expect(multipart.mediaType).to.equal("multipart/mixed");
         });
-
-        it("should accept only valid boundaries", function () {
-            expect(() => new Multipart([], "")).to.throw(RangeError, "Invalid boundary");
-            expect(() => new Multipart([], " ")).to.throw(RangeError, "Invalid boundary");
-            expect(() => new Multipart([], "a ")).to.throw(RangeError, "Invalid boundary");
-            expect(() => new Multipart([], "0123456789".repeat(7) + "0")).to.throw(RangeError, "Invalid boundary");
-            expect(() => new Multipart([], "foo!bar")).to.throw(RangeError, "Invalid boundary");
-
-            expect(() => new Multipart([], "a")).to.not.throw();
-            expect(() => new Multipart([], "0123456789".repeat(7))).to.not.throw();
-            expect(() => new Multipart([], "foo bar")).to.not.throw();
-            expect(() => new Multipart([], "foo'bar")).to.not.throw();
-            expect(() => new Multipart([], "foo(bar")).to.not.throw();
-            expect(() => new Multipart([], "foo)bar")).to.not.throw();
-            expect(() => new Multipart([], "foo+bar")).to.not.throw();
-            expect(() => new Multipart([], "foo_bar")).to.not.throw();
-            expect(() => new Multipart([], "foo,bar")).to.not.throw();
-            expect(() => new Multipart([], "foo-bar")).to.not.throw();
-            expect(() => new Multipart([], "foo.bar")).to.not.throw();
-            expect(() => new Multipart([], "foo/bar")).to.not.throw();
-            expect(() => new Multipart([], "foo:bar")).to.not.throw();
-            expect(() => new Multipart([], "foo=bar")).to.not.throw();
-            expect(() => new Multipart([], "foo?bar")).to.not.throw();
-        });
     });
 
     describe("parse", function () {
@@ -276,5 +252,29 @@ describe("Multipart", function () {
 
             expect(new TextDecoder().decode(bytes)).to.equal(new TextDecoder().decode(expectedBytes));
         });
+
+        it("should accept only valid boundaries", function () {
+            expect(() => new Multipart([], "").bytes()).to.throw(RangeError, "Invalid boundary");
+            expect(() => new Multipart([], " ").bytes()).to.throw(RangeError, "Invalid boundary");
+            expect(() => new Multipart([], "a ").bytes()).to.throw(RangeError, "Invalid boundary");
+            expect(() => new Multipart([], "0123456789".repeat(7) + "0").bytes()).to.throw(RangeError, "Invalid boundary");
+            expect(() => new Multipart([], "foo!bar").bytes()).to.throw(RangeError, "Invalid boundary");
+
+            expect(() => new Multipart([], "a").bytes()).to.not.throw();
+            expect(() => new Multipart([], "0123456789".repeat(7)).bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo'bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo(bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo)bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo+bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo_bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo,bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo-bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo.bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo/bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo:bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo=bar").bytes()).to.not.throw();
+            expect(() => new Multipart([], "foo?bar").bytes()).to.not.throw();
+        });
     });
 });