2 files changed, 18 insertions, 10 deletions
diff --git a/std/mime/multipart.ts b/std/mime/multipart.ts
index d88ff3d13..7113af012 100644
--- a/std/mime/multipart.ts
+++ b/std/mime/multipart.ts
@@ -12,7 +12,7 @@ import { extname } from "../path/mod.ts";
 import { tempFile } from "../io/util.ts";
 import { BufReader, BufWriter, UnexpectedEOFError } from "../io/bufio.ts";
 import { encoder } from "../strings/mod.ts";
-import { assertStrictEq } from "../testing/asserts.ts";
+import { assertStrictEq, assert } from "../testing/asserts.ts";
 import { TextProtoReader } from "../textproto/mod.ts";
 import { hasOwnProperty } from "../util/has_own_property.ts";
 
@@ -205,7 +205,8 @@ class PartReader implements Reader, Closer {
     if (this.contentDispositionParams) return this.contentDispositionParams;
     const cd = this.headers.get("content-disposition");
     const params: { [key: string]: string } = {};
-    const comps = cd!.split(";");
+    assert(cd != null, "content-disposition must be set");
+    const comps = cd.split(";");
     this.contentDisposition = comps[0];
     comps
       .slice(1)
@@ -265,10 +266,12 @@ export class MultipartReader {
   /** Read all form data from stream.
    * If total size of stored data in memory exceed maxMemory,
    * overflowed file data will be written to temporal files.
-   * String field values are never written to files */
+   * String field values are never written to files.
+   * null value means parsing or writing to file was failed in some reason.
+   *  */
   async readForm(
     maxMemory: number
-  ): Promise<{ [key: string]: string | FormFile }> {
+  ): Promise<{ [key: string]: null | string | FormFile }> {
     const result = Object.create(null);
     let maxValueBytes = maxMemory + (10 << 20);
     const buf = new Buffer(new Uint8Array(maxValueBytes));
@@ -293,8 +296,10 @@ export class MultipartReader {
         continue;
       }
       // file
-      let formFile: FormFile;
+      let formFile: FormFile | null = null;
       const n = await copy(buf, p);
+      const contentType = p.headers.get("content-type");
+      assert(contentType != null, "content-type must be set");
       if (n > maxMemory) {
         // too big, write to disk and flush buffer
         const ext = extname(p.fileName);
@@ -311,7 +316,7 @@ export class MultipartReader {
           file.close();
           formFile = {
             filename: p.fileName,
-            type: p.headers.get("content-type")!,
+            type: contentType,
             tempfile: filepath,
             size
           };
@@ -321,14 +326,14 @@ export class MultipartReader {
       } else {
         formFile = {
           filename: p.fileName,
-          type: p.headers.get("content-type")!,
+          type: contentType,
           content: buf.bytes(),
           size: buf.length
         };
         maxMemory -= n;
         maxValueBytes -= n;
       }
-      result[p.formName] = formFile!;
+      result[p.formName] = formFile;
     }
     return result;
   }
diff --git a/std/mime/multipart_test.ts b/std/mime/multipart_test.ts
index 869932fbf..d3e49aa4d 100644
--- a/std/mime/multipart_test.ts
+++ b/std/mime/multipart_test.ts
@@ -199,7 +199,8 @@ test(async function multipartMultipartReader2(): Promise<void> {
     assertEquals(form["bar"], "bar");
     const file = form["file"] as FormFile;
     assertEquals(file.type, "application/octet-stream");
-    const f = await open(file.tempfile!);
+    assert(file.tempfile != null);
+    const f = await open(file.tempfile);
     const w = new StringWriter();
     await copy(w, f);
     const json = JSON.parse(w.toString());
@@ -207,7 +208,9 @@ test(async function multipartMultipartReader2(): Promise<void> {
     f.close();
   } finally {
     const file = form["file"] as FormFile;
-    await remove(file.tempfile!);
+    if (file.tempfile) {
+      await remove(file.tempfile);
+    }
   }
 });