Fix response size calculation

The `response.size` is almost always set to `0`. However, the
`Content-Length` header is returned by Azure and contains the size of
the file.

extensions/ql-vscode/src/remote-queries/variant-analysis-results-manager.ts

@@ -90,12 +90,18 @@ export class VariantAnalysisResultsManager extends DisposableObject {
     const zipFilePath = join(resultDirectory, "results.zip");
 
     const response = await fetch(repoTask.artifactUrl);
+
+    let responseSize = parseInt(response.headers.get("content-length") || "0");
+    if (responseSize === 0 && response.size > 0) {
+      responseSize = response.size;
+    }
+
     let amountDownloaded = 0;
     for await (const chunk of response.body) {
       await appendFile(zipFilePath, Buffer.from(chunk));
       amountDownloaded += chunk.length;
       await onDownloadPercentageChanged(
-        Math.floor((amountDownloaded / response.size) * 100),
+        Math.floor((amountDownloaded / responseSize) * 100),
       );
     }
 

extensions/ql-vscode/test/vscode-tests/cli-integration/remote-queries/variant-analysis-results-manager.test.ts

@@ -169,7 +169,10 @@ describe(VariantAnalysisResultsManager.name, () => {
           (url: RequestInfo, _init?: RequestInit) => {
             if (url === dummyRepoTask.artifactUrl) {
               const response = new Response(Readable.from(generateInParts()));
-              response.size = fileContents.length;
+              response.headers.set(
+                "Content-Length",
+                fileContents.length.toString(),
+              );
               return Promise.resolve(response);
             }
             return Promise.reject(new Error("Unexpected artifact URL"));