From c77bd88259dac6e6b7bcb29425905467aa2ef66f Mon Sep 17 00:00:00 2001
From: eldritch horrors <pennae@lix.systems>
Date: Sat, 27 Apr 2024 19:55:54 +0200
Subject: [PATCH] libstore: de-callback-ify BinaryCacheStore::getFile

Change-Id: I36b3eb9f645aa04058151e7b2353e15e6f29057b
---
 src/libstore/binary-cache-store.cc      | 69 +++++++------------------
 src/libstore/binary-cache-store.hh      | 10 +---
 src/libstore/http-binary-cache-store.cc | 33 ++++--------
 3 files changed, 29 insertions(+), 83 deletions(-)

diff --git a/src/libstore/binary-cache-store.cc b/src/libstore/binary-cache-store.cc
index 502fac05f..bf7265c35 100644
--- a/src/libstore/binary-cache-store.cc
+++ b/src/libstore/binary-cache-store.cc
@@ -67,26 +67,9 @@ void BinaryCacheStore::upsertFile(const std::string & path,
     upsertFile(path, std::make_shared<std::stringstream>(std::move(data)), mimeType);
 }
 
-void BinaryCacheStore::getFile(const std::string & path,
-    Callback<std::optional<std::string>> callback) noexcept
-{
-    try {
-        callback(getFile(path));
-    } catch (...) { callback.rethrow(); }
-}
-
 void BinaryCacheStore::getFile(const std::string & path, Sink & sink)
 {
-    std::promise<std::optional<std::string>> promise;
-    getFile(path,
-        {[&](std::future<std::optional<std::string>> result) {
-            try {
-                promise.set_value(result.get());
-            } catch (...) {
-                promise.set_exception(std::current_exception());
-            }
-        }});
-    sink(*promise.get_future().get());
+    sink(*getFile(path));
 }
 
 std::optional<std::string> BinaryCacheStore::getFile(const std::string & path)
@@ -377,25 +360,17 @@ void BinaryCacheStore::queryPathInfoUncached(const StorePath & storePath,
 
     auto narInfoFile = narInfoFileFor(storePath);
 
-    auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
+    try {
+        auto data = getFile(narInfoFile);
 
-    getFile(narInfoFile,
-        {[=,this](std::future<std::optional<std::string>> fut) {
-            try {
-                auto data = fut.get();
+        if (!data) return callback({});
 
-                if (!data) return (*callbackPtr)({});
+        stats.narInfoRead++;
 
-                stats.narInfoRead++;
-
-                (*callbackPtr)((std::shared_ptr<ValidPathInfo>)
-                    std::make_shared<NarInfo>(*this, *data, narInfoFile));
-
-                (void) act; // force Activity into this lambda to ensure it stays alive
-            } catch (...) {
-                callbackPtr->rethrow();
-            }
-        }});
+        callback(std::make_shared<NarInfo>(*this, *data, narInfoFile));
+    } catch (...) {
+        callback.rethrow();
+    }
 }
 
 StorePath BinaryCacheStore::addToStore(
@@ -477,24 +452,16 @@ void BinaryCacheStore::queryRealisationUncached(const DrvOutput & id,
 {
     auto outputInfoFilePath = realisationsPrefix + "/" + id.to_string() + ".doi";
 
-    auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
+    try {
+        auto data = getFile(outputInfoFilePath);
+        if (!data) return callback({});
 
-    Callback<std::optional<std::string>> newCallback = {
-        [=](std::future<std::optional<std::string>> fut) {
-            try {
-                auto data = fut.get();
-                if (!data) return (*callbackPtr)({});
-
-                auto realisation = Realisation::fromJSON(
-                    nlohmann::json::parse(*data), outputInfoFilePath);
-                return (*callbackPtr)(std::make_shared<const Realisation>(realisation));
-            } catch (...) {
-                callbackPtr->rethrow();
-            }
-        }
-    };
-
-    getFile(outputInfoFilePath, std::move(newCallback));
+        auto realisation = Realisation::fromJSON(
+            nlohmann::json::parse(*data), outputInfoFilePath);
+        return callback(std::make_shared<const Realisation>(realisation));
+    } catch (...) {
+        callback.rethrow();
+    }
 }
 
 void BinaryCacheStore::registerDrvOutput(const Realisation& info) {
diff --git a/src/libstore/binary-cache-store.hh b/src/libstore/binary-cache-store.hh
index 218a888e3..af2b50084 100644
--- a/src/libstore/binary-cache-store.hh
+++ b/src/libstore/binary-cache-store.hh
@@ -85,15 +85,7 @@ public:
      */
     virtual void getFile(const std::string & path, Sink & sink);
 
-    /**
-     * Fetch the specified file and call the specified callback with
-     * the result. A subclass may implement this asynchronously.
-     */
-    virtual void getFile(
-        const std::string & path,
-        Callback<std::optional<std::string>> callback) noexcept;
-
-    std::optional<std::string> getFile(const std::string & path);
+    virtual std::optional<std::string> getFile(const std::string & path);
 
 public:
 
diff --git a/src/libstore/http-binary-cache-store.cc b/src/libstore/http-binary-cache-store.cc
index 9b980d81f..764f97fc1 100644
--- a/src/libstore/http-binary-cache-store.cc
+++ b/src/libstore/http-binary-cache-store.cc
@@ -165,33 +165,20 @@ protected:
         }
     }
 
-    void getFile(const std::string & path,
-        Callback<std::optional<std::string>> callback) noexcept override
+    std::optional<std::string> getFile(const std::string & path) override
     {
-        try {
-            checkEnabled();
-        } catch (...) {
-            callback.rethrow();
-            return;
-        }
+        checkEnabled();
 
         auto request(makeRequest(path));
 
-        auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
-
-        getFileTransfer()->enqueueFileTransfer(request,
-            {[callbackPtr, this](std::future<FileTransferResult> result) {
-                try {
-                    (*callbackPtr)(std::move(result.get().data));
-                } catch (FileTransferError & e) {
-                    if (e.error == FileTransfer::NotFound || e.error == FileTransfer::Forbidden)
-                        return (*callbackPtr)({});
-                    maybeDisable();
-                    callbackPtr->rethrow();
-                } catch (...) {
-                    callbackPtr->rethrow();
-                }
-            }});
+        try {
+            return std::move(getFileTransfer()->enqueueFileTransfer(request).get().data);
+        } catch (FileTransferError & e) {
+            if (e.error == FileTransfer::NotFound || e.error == FileTransfer::Forbidden)
+                return {};
+            maybeDisable();
+            throw;
+        }
     }
 
     /**