Ensure config builders always have a valid state

...by making the respective Build methods const. It should be
perfectly valid for multiple Build calls to happen for the same
builder instance, so its internal state should never be invalidated
by, e.g., moving from internal fields.

2 files changed, 9 insertions, 3 deletions

diff --git a/src/buildtool/auth/authentication.hpp b/src/buildtool/auth/authentication.hpp
index cd4ff86d..f06e6a1c 100644
--- a/src/buildtool/auth/authentication.hpp
+++ b/src/buildtool/auth/authentication.hpp
@@ -84,7 +84,7 @@ class Auth::TLS::Builder final {
     /// tls_client_key are set, or none of the two.
     /// \return Auth on success, error string on failure, nullopt if no TLS
     /// configuration fields were set.
-    [[nodiscard]] auto Build() noexcept
+    [[nodiscard]] auto Build() const noexcept
         -> std::optional<expected<Auth, std::string>> {
         // To not duplicate default arguments of Auth::TLS in builder,
         // create a default config and copy default arguments from there.
diff --git a/src/buildtool/serve_api/remote/config.hpp b/src/buildtool/serve_api/remote/config.hpp
index d19e7699..005d56af 100644
--- a/src/buildtool/serve_api/remote/config.hpp
+++ b/src/buildtool/serve_api/remote/config.hpp
@@ -17,6 +17,7 @@
 
 #include <chrono>
 #include <cstddef>
+#include <exception>
 #include <filesystem>
 #include <iterator>
 #include <optional>
@@ -93,7 +94,7 @@ class RemoteServeConfig::Builder final {
 
     /// \brief Finalize building and create RemoteServeConfig.
     /// \return RemoteServeConfig on success or an error on failure.
-    [[nodiscard]] auto Build() noexcept
+    [[nodiscard]] auto Build() const noexcept
         -> expected<RemoteServeConfig, std::string> {
         // To not duplicate default arguments of RemoteServeConfig in builder,
         // create a default config and copy default arguments from there.
@@ -111,7 +112,12 @@ class RemoteServeConfig::Builder final {
 
         auto known_repositories = default_config.known_repositories;
         if (known_repositories_.has_value()) {
-            known_repositories = std::move(*known_repositories_);
+            try {
+                known_repositories = *known_repositories_;
+            } catch (std::exception const& ex) {
+                return unexpected{
+                    std::string("Setting known repositories failed.")};
+            }
         }
 
         auto jobs = default_config.jobs;