libstore: remove FileTransfer::enqueueDownload

it's no longer needed. `download` can do everything `enqueueDownload`
did, and a lot more. e.g. not block the calling thread, for instance.

Change-Id: I4b36235ed707c92d117b4c33efa3db50d26f9a84

src/libfetchers/tarball.cc

@@ -45,7 +45,9 @@ DownloadFileResult downloadFile(
     FileTransferResult res;
     std::string data;
     try {
-        std::tie(res, data) = getFileTransfer()->enqueueDownload(url, headers).get();
+        auto [meta, content] = getFileTransfer()->download(url, headers);
+        res = std::move(meta);
+        data = content->drain();
     } catch (FileTransferError & e) {
         if (cached) {
             warn("%s; using cached version", e.msg());

src/libstore/filetransfer.cc

@@ -700,12 +700,6 @@ struct curlFileTransfer : public FileTransfer
     }
 #endif
 
-    std::future<std::pair<FileTransferResult, std::string>>
-    enqueueDownload(const std::string & uri, const Headers & headers = {}) override
-    {
-        return enqueueFileTransfer(uri, headers, std::nullopt, false);
-    }
-
     void upload(const std::string & uri, std::string data, const Headers & headers) override
     {
         enqueueFileTransfer(uri, headers, std::move(data), false).get();

src/libstore/filetransfer.hh

@@ -69,13 +69,6 @@ struct FileTransfer
 {
     virtual ~FileTransfer() { }
 
-    /**
-     * Enqueues a download request, returning a future for the result of
-     * the download. The future may throw a FileTransferError exception.
-     */
-    virtual std::future<std::pair<FileTransferResult, std::string>>
-    enqueueDownload(const std::string & uri, const Headers & headers = {}) = 0;
-
     /**
      * Upload some data. May throw a FileTransferError exception.
      */

src/libstore/http-binary-cache-store.cc

@@ -161,7 +161,7 @@ protected:
         checkEnabled();
 
         try {
-            return std::move(getFileTransfer()->enqueueDownload(makeURI(path)).get().second);
+            return getFileTransfer()->download(makeURI(path)).second->drain();
         } catch (FileTransferError & e) {
             if (e.error == FileTransfer::NotFound || e.error == FileTransfer::Forbidden)
                 return {};

src/nix/upgrade-nix.cc

@@ -285,7 +285,8 @@ struct CmdUpgradeNix : MixDryRun, EvalCommand
         Activity act(*logger, lvlInfo, actUnknown, "querying latest Nix version");
 
         // FIXME: use nixos.org?
-        auto [res, data] = getFileTransfer()->enqueueDownload(storePathsUrl).get();
+        auto [res, content] = getFileTransfer()->download(storePathsUrl);
+        auto data = content->drain();
 
         auto state = std::make_unique<EvalState>(SearchPath{}, store);
         auto v = state->allocValue();

tests/unit/libstore/filetransfer.cc

@@ -163,7 +163,7 @@ TEST(FileTransfer, NOT_ON_DARWIN(reportsSetupErrors))
     auto [port, srv] = serveHTTP("404 not found", "", [] { return ""; });
     auto ft = makeFileTransfer();
     ASSERT_THROW(
-        ft->enqueueDownload(fmt("http://[::1]:%d/index", port)).get(),
+        ft->download(fmt("http://[::1]:%d/index", port)),
         FileTransferError
     );
 }
@@ -215,7 +215,7 @@ TEST(FileTransfer, usesIntermediateLinkHeaders)
         {"200 ok", "content-length: 1\r\n", [] { return "a"; }},
     });
     auto ft = makeFileTransfer(0);
-    auto [result, _data] = ft->enqueueDownload(fmt("http://[::1]:%d/first", port)).get();
+    auto [result, _data] = ft->download(fmt("http://[::1]:%d/first", port));
     ASSERT_EQ(result.immutableUrl, "http://foo");
 }