Download testing emulators using a buffer

scripts/emulator-testing/dataconnect-test-runner.ts

@@ -18,6 +18,7 @@
 import { DataConnectEmulator } from './emulators/dataconnect-emulator';
 import { spawn } from 'child-process-promise';
 import * as path from 'path';
+
 function runTest(port: number) {
   console.log(
     'path: ' + path.resolve(__dirname, '../../packages/data-connect')
@@ -38,7 +39,7 @@ async function run(): Promise<void> {
     await emulator.setUp();
     await runTest(emulator.port);
   } finally {
-    await emulator.tearDown();
+    emulator.tearDown();
   }
 }
 run().catch(err => {

scripts/emulator-testing/emulators/dataconnect-emulator.ts

@@ -21,8 +21,6 @@ import { Emulator } from './emulator';
 const DATABASE_EMULATOR_VERSION = '1.3.7';
 
 export class DataConnectEmulator extends Emulator {
-  //   namespace: string;
-
   constructor(port = 3628) {
     const os = platform();
     let urlString = '';

scripts/emulator-testing/emulators/emulator.ts

@@ -53,64 +53,73 @@ export abstract class Emulator {
       return Promise.resolve();
     }
 
+    console.log(`Downloading emulator from [${this.binaryUrl}] ...`);
+    const { name: tempDir } = tmp.dirSync({ unsafeCleanup: true });
+    const filepath = path.resolve(tempDir, this.binaryName);
+    let cur = 0;
+    let buf = new Uint8Array(2 ** 26);
     return new Promise<void>((resolve, reject) => {
-      tmp.dir((err: Error | null, dir: string) => {
-        if (err) reject(err);
-        console.log(`Created temporary directory at [${dir}].`);
-        const filepath: string = path.resolve(dir, this.binaryName);
-        const writer = fs.createWriteStream(filepath);
-        console.log(`Downloading emulator from [${this.binaryUrl}] ...`);
-        // Map the DOM's fetch Reader to node's streaming file system
-        // operations. We will need to access class members `binaryPath` and `copyToCache` after the
-        // download completes. It's a compilation error to pass `this` into the named function
-        // `readChunk`, so the download operation is wrapped in a promise that we wait upon.
-        const downloadPromise = new Promise<void>(
-          (downloadComplete, downloadFailed) => {
-            fetch(this.binaryUrl)
-              .then(resp => {
-                if (resp.status !== 200 || resp.body === null) {
-                  console.log('Download of emulator failed: ', resp.statusText);
-                  downloadFailed();
-                } else {
-                  const reader = resp.body.getReader();
-                  reader.read().then(function readChunk({ done, value }): any {
-                    if (done) {
-                      downloadComplete();
-                    } else {
-                      writer.write(value);
-                      return reader.read().then(readChunk);
-                    }
-                  });
+      /**
+       * Once the download is `done` in `readChunk`, we want to set `this.binaryPath` to the path of the
+       * downloaded emulator. Unfortunately, we can't access `this` when inside `readChunk`'s scope, since
+       * it's a named function expression, and does not inherit the `this` object from it's parent.
+       * To work around this, we wrap the fetch in a promise,
+       * then once it's resolved we can access `this` in a callback arrow function that *does* inherit
+       * `this` from the parent object, allowing us to set `this.binaryPath`.
+       * Note that we can't make readChunk an arrow function, since it needs to be named so that we can
+       * perform recursion to read the next chunk.
+       */
+      const downloadPromise = new Promise<void>(
+        (downloadComplete, downloadFailed) => {
+          fetch(this.binaryUrl)
+            .then(resp => {
+              if (!resp.ok || resp.body === null) {
+                return downloadFailed(
+                  `Failed to download emulator: [${resp.status}] ${resp.statusText}`
+                );
+              }
+
+              const reader = resp.body.getReader();
+              reader.read().then(function readChunk({ done, value }): any {
+                if (done) {
+                  return downloadComplete();
+                }
+
+                if (!value) {
+                  return downloadFailed(
+                    'Did not receive chunk in response body'
+                  );
                 }
-              })
-              .catch(e => {
-                console.log(`Download of emulator failed: ${e}`);
-                downloadFailed();
+
+                buf.set(value, cur);
+                cur += value.length;
+                return reader.read().then(readChunk);
               });
-          }
-        );
+            })
+            .catch(err => downloadFailed(err));
+        }
+      );
+
+      downloadPromise
+        .then(() => {
+          console.log('Download complete.');
+          fs.writeFileSync(filepath, buf.slice(0, cur));
+          fs.chmod(filepath, 0o755, err => {
+            if (err) {
+              return reject(err);
+            }
 
-        downloadPromise.then(
-          () => {
-            console.log('Download complete');
-            // Change emulator binary file permission to 'rwxr-xr-x'.
-            // The execute permission is required for it to be able to start
-            // with 'java -jar'.
-            fs.chmod(filepath, 0o755, err => {
-              if (err) reject(err);
-              console.log(`Changed emulator file permissions to 'rwxr-xr-x'.`);
-              this.binaryPath = filepath;
-              if (this.copyToCache()) {
-                console.log(`Cached emulator at ${this.cacheBinaryPath}`);
-              }
-              resolve();
-            });
-          },
-          () => {
-            reject();
-          }
-        );
-      });
+            console.log(`Changed emulator file permissions to 'rwxr-xr-x'.`);
+            // Since we are now in an arrow function, `this` is inherited from the `download()` method, so it is the Emulator object
+            this.binaryPath = filepath;
+            if (this.copyToCache()) {
+              console.log(`Cached emulator at ${this.cacheBinaryPath}`);
+            }
+
+            resolve();
+          });
+        })
+        .catch(err => reject(err));
     });
   }
 
@@ -184,7 +193,7 @@ export abstract class Emulator {
     }
 
     if (this.binaryPath) {
-      console.log(`Deleting the emulator jar at ${this.binaryPath}`);
+      console.log(`Deleting the emulator at ${this.binaryPath}`);
       fs.unlinkSync(this.binaryPath);
     }
   }