feat: don't read full file if range header is present

src/middleware.js

@@ -48,15 +48,15 @@ export default function wrapper(context) {
         headers = headers(req, res, context);
       }
 
-      let content;
+      let fileSize;
 
       if (!filename) {
         await goNext();
         return;
       }
 
       try {
-        content = context.outputFileSystem.readFileSync(filename);
+        fileSize = context.outputFileSystem.lstatSync(filename).size;
       } catch (_ignoreError) {
         await goNext();
         return;
@@ -100,21 +100,24 @@ export default function wrapper(context) {
       }
 
       // Buffer
-      content = handleRangeHeaders(context, content, req, res);
-
-      // Express API
-      if (res.send) {
-        res.send(content);
-      }
-      // Node.js API
-      else {
-        res.setHeader("Content-Length", content.length);
-
-        if (req.method === "HEAD") {
-          res.end();
-        } else {
-          res.end(content);
-        }
+      const ranges = handleRangeHeaders(context, fileSize, req, res);
+      const stream = context.outputFileSystem.createReadStream(
+        filename,
+        ranges
+          ? {
+              start: ranges.start,
+              end: ranges.end,
+            }
+          : {}
+      );
+
+      const responseSize = ranges ? 1 + (ranges.end - ranges.start) : fileSize;
+      res.setHeader("Content-Length", responseSize);
+
+      if (req.method === "HEAD") {
+        res.end();
+      } else {
+        stream.pipe(res);
       }
     }
   };

src/utils/handleRangeHeaders.js

@@ -1,6 +1,6 @@
 import parseRange from "range-parser";
 
-export default function handleRangeHeaders(context, content, req, res) {
+export default function handleRangeHeaders(context, size, req, res) {
   // assumes express API. For other servers, need to add logic to access
   // alternative header APIs
   if (res.set) {
@@ -21,20 +21,20 @@ export default function handleRangeHeaders(context, content, req, res) {
   }
 
   if (range) {
-    const ranges = parseRange(content.length, range);
+    const ranges = parseRange(size, range);
 
     // unsatisfiable
     if (ranges === -1) {
       // Express API
       if (res.set) {
-        res.set("Content-Range", `bytes */${content.length}`);
+        res.set("Content-Range", `bytes */${size}`);
         res.status(416);
       }
       // Node.js API
       else {
         // eslint-disable-next-line no-param-reassign
         res.statusCode = 416;
-        res.setHeader("Content-Range", `bytes */${content.length}`);
+        res.setHeader("Content-Range", `bytes */${size}`);
       }
     } else if (ranges === -2) {
       // malformed header treated as regular response
@@ -47,16 +47,13 @@ export default function handleRangeHeaders(context, content, req, res) {
         "A Range header with multiple ranges was provided. Multiple ranges are not supported, so a regular response will be sent for this request."
       );
     } else {
-      // valid range header
-      const { length } = content;
-
       // Express API
       if (res.set) {
         // Content-Range
         res.status(206);
         res.set(
           "Content-Range",
-          `bytes ${ranges[0].start}-${ranges[0].end}/${length}`
+          `bytes ${ranges[0].start}-${ranges[0].end}/${size}`
         );
       }
       // Node.js API
@@ -66,14 +63,13 @@ export default function handleRangeHeaders(context, content, req, res) {
         res.statusCode = 206;
         res.setHeader(
           "Content-Range",
-          `bytes ${ranges[0].start}-${ranges[0].end}/${length}`
+          `bytes ${ranges[0].start}-${ranges[0].end}/${size}`
         );
       }
 
-      // eslint-disable-next-line no-param-reassign
-      content = content.slice(ranges[0].start, ranges[0].end + 1);
+      return ranges[0];
     }
   }
 
-  return content;
+  return null;
 }

test/middleware.test.js

@@ -231,23 +231,43 @@ describe.each([
         });
 
         it('should return the "206" code for the "GET" request with the valid range header', (done) => {
+          const fileData = instance.context.outputFileSystem.readFileSync(
+            path.resolve(outputPath, "bundle.js"),
+            "utf8"
+          );
           request(app)
             .get("/bundle.js")
             .set("Range", "bytes=3000-3500")
             .expect("Content-Length", "501")
             .expect("Content-Range", `bytes 3000-3500/${codeLength}`)
-            .expect(206, done);
+            .expect(206)
+            .then((response) => {
+              expect(response.text).toBe(fileData.substr(3000, 501));
+              expect(response.text.length).toBe(501);
+              done();
+            });
         });
 
         it('should return the "200" code for the "GET" request with malformed range header which is ignored', (done) => {
-          request(app).get("/bundle.js").set("Range", "abc").expect(200, done);
+          request(app)
+            .get("/bundle.js")
+            .set("Range", "abc")
+            .expect(200)
+            .then((response) => {
+              expect(response.text.length).toBe(codeLength);
+              done();
+            });
         });
 
         it('should return the "200" code for the "GET" request with multiple range header which is ignored', (done) => {
           request(app)
             .get("/bundle.js")
             .set("Range", "bytes=3000-3100,3200-3300")
-            .expect(200, done);
+            .expect(200)
+            .then((response) => {
+              expect(response.text.length).toBe(codeLength);
+              done();
+            });
         });
 
         it('should return the "404" code for the "GET" request with to the non-public path', (done) => {

test/utils/__snapshots__/handleRangeHeaders.test.js.snap.webpack4

@@ -17,15 +17,15 @@ Array [
 ]
 `;
 
-exports[`handleRangeHeaders should handle multiple ranges 1`] = `
+exports[`handleRangeHeaders should handle multiple ranges by sending a regular response 1`] = `
 Array [
   Array [
     "A Range header with multiple ranges was provided. Multiple ranges are not supported, so a regular response will be sent for this request.",
   ],
 ]
 `;
 
-exports[`handleRangeHeaders should handle multiple ranges 2`] = `
+exports[`handleRangeHeaders should handle multiple ranges by sending a regular response 2`] = `
 Array [
   Array [
     "Accept-Ranges",

test/utils/__snapshots__/handleRangeHeaders.test.js.snap.webpack5

@@ -17,15 +17,15 @@ Array [
 ]
 `;
 
-exports[`handleRangeHeaders should handle multiple ranges 1`] = `
+exports[`handleRangeHeaders should handle multiple ranges by sending a regular response 1`] = `
 Array [
   Array [
     "A Range header with multiple ranges was provided. Multiple ranges are not supported, so a regular response will be sent for this request.",
   ],
 ]
 `;
 
-exports[`handleRangeHeaders should handle multiple ranges 2`] = `
+exports[`handleRangeHeaders should handle multiple ranges by sending a regular response 2`] = `
 Array [
   Array [
     "Accept-Ranges",

test/utils/handleRangeHeaders.test.js

@@ -29,8 +29,8 @@ describe("handleRangeHeaders", () => {
       },
     };
 
-    const contentRes = handleRangeHeaders(context, content, req, res);
-    expect(contentRes).toEqual("bcde");
+    const ranges = handleRangeHeaders(context, content.length, req, res);
+    expect(ranges).toEqual({ start: 1, end: 4 });
     expect(res.statusCode).toEqual(206);
     expect(res.set.mock.calls).toMatchSnapshot();
   });
@@ -53,8 +53,8 @@ describe("handleRangeHeaders", () => {
       },
     };
 
-    const contentRes = handleRangeHeaders(context, content, req, res);
-    expect(contentRes).toEqual("abcdef");
+    const ranges = handleRangeHeaders(context, content, req, res);
+    expect(ranges).toEqual(null);
     expect(context.logger.error.mock.calls).toMatchSnapshot();
     expect(res.statusCode).toBeUndefined();
     expect(res.set.mock.calls).toMatchSnapshot();
@@ -78,13 +78,13 @@ describe("handleRangeHeaders", () => {
       },
     };
 
-    const contentRes = handleRangeHeaders(context, content, req, res);
-    expect(contentRes).toEqual("abcdef");
+    const ranges = handleRangeHeaders(context, content.length, req, res);
+    expect(ranges).toEqual(null);
     expect(res.statusCode).toEqual(416);
     expect(res.set.mock.calls).toMatchSnapshot();
   });
 
-  it("should handle multiple ranges", () => {
+  it("should handle multiple ranges by sending a regular response", () => {
     const content = "abcdef";
     const req = {
       headers: {
@@ -102,8 +102,8 @@ describe("handleRangeHeaders", () => {
       },
     };
 
-    const contentRes = handleRangeHeaders(context, content, req, res);
-    expect(contentRes).toEqual("abcdef");
+    const ranges = handleRangeHeaders(context, content.length, req, res);
+    expect(ranges).toEqual(null);
     expect(context.logger.error.mock.calls).toMatchSnapshot();
     expect(res.statusCode).toBeUndefined();
     expect(res.set.mock.calls).toMatchSnapshot();