execution_response: Allow failures to be reported while populating

As populating the containers from remote response only takes place
once, no assumptions should be made that this cannot fail (for
example if wrong or invalid entries were produced). Instead, return
error messages on failure to callers that can log accordingly.

8 files changed, 144 insertions, 52 deletions

diff --git a/src/buildtool/execution_api/common/TARGETS b/src/buildtool/execution_api/common/TARGETS
index b417e26a..0f3288e5 100644
--- a/src/buildtool/execution_api/common/TARGETS
+++ b/src/buildtool/execution_api/common/TARGETS
@@ -21,6 +21,7 @@
     , ["src/buildtool/file_system", "file_system_manager"]
     , ["src/buildtool/logging", "log_level"]
     , ["src/buildtool/logging", "logging"]
+    , ["src/utils/cpp", "expected"]
     , ["src/utils/cpp", "gsl"]
     , ["src/utils/cpp", "hex_string"]
     , ["src/buildtool/file_system", "git_repo"]
diff --git a/src/buildtool/execution_api/common/execution_response.hpp b/src/buildtool/execution_api/common/execution_response.hpp
index ca1f34a1..c0aa16f8 100644
--- a/src/buildtool/execution_api/common/execution_response.hpp
+++ b/src/buildtool/execution_api/common/execution_response.hpp
@@ -23,6 +23,7 @@
 
 #include "gsl/gsl"
 #include "src/buildtool/common/artifact.hpp"
+#include "src/utils/cpp/expected.hpp"
 
 /// \brief Abstract response.
 /// Response of an action execution. Contains outputs from multiple commands and
@@ -60,9 +61,10 @@ class IExecutionResponse {
     [[nodiscard]] virtual auto ActionDigest() const noexcept
         -> std::string const& = 0;
 
-    [[nodiscard]] virtual auto Artifacts() noexcept -> ArtifactInfos const& = 0;
+    [[nodiscard]] virtual auto Artifacts() noexcept
+        -> expected<gsl::not_null<ArtifactInfos const*>, std::string> = 0;
     [[nodiscard]] virtual auto DirectorySymlinks() noexcept
-        -> DirSymlinks const& = 0;
+        -> expected<gsl::not_null<DirSymlinks const*>, std::string> = 0;
 };
 
 #endif  // INCLUDED_SRC_BUILDTOOL_EXECUTION_API_COMMON_REMOTE_EXECUTION_RESPONSE_HPP
diff --git a/src/buildtool/execution_api/execution_service/execution_server.cpp b/src/buildtool/execution_api/execution_service/execution_server.cpp
index 61fd3434..d59eb91f 100644
--- a/src/buildtool/execution_api/execution_service/execution_server.cpp
+++ b/src/buildtool/execution_api/execution_service/execution_server.cpp
@@ -94,8 +94,16 @@ auto ExecutionServiceImpl::ToIExecutionAction(
 auto ExecutionServiceImpl::ToBazelExecuteResponse(
     IExecutionResponse::Ptr const& i_execution_response) const noexcept
     -> expected<::bazel_re::ExecuteResponse, std::string> {
-    auto result = ToBazelActionResult(i_execution_response->Artifacts(),
-                                      i_execution_response->DirectorySymlinks(),
+    auto artifacts = i_execution_response->Artifacts();
+    if (not artifacts) {
+        return unexpected{std::move(artifacts).error()};
+    }
+    auto dir_symlinks = i_execution_response->DirectorySymlinks();
+    if (not dir_symlinks) {
+        return unexpected{std::move(dir_symlinks).error()};
+    }
+    auto result = ToBazelActionResult(*std::move(artifacts).value(),
+                                      *std::move(dir_symlinks).value(),
                                       storage_);
     if (not result) {
         return unexpected{std::move(result).error()};
diff --git a/src/buildtool/execution_api/local/TARGETS b/src/buildtool/execution_api/local/TARGETS
index 66a57f21..9bf9de97 100644
--- a/src/buildtool/execution_api/local/TARGETS
+++ b/src/buildtool/execution_api/local/TARGETS
@@ -43,6 +43,7 @@
     , ["src/buildtool/logging", "logging"]
     , ["src/buildtool/execution_api/execution_service", "cas_utils"]
     , ["src/buildtool/file_system", "git_repo"]
+    , ["src/utils/cpp", "expected"]
     , ["src/utils/cpp", "tmp_dir"]
     , ["src/buildtool/crypto", "hash_function"]
     ]
diff --git a/src/buildtool/execution_api/local/local_response.hpp b/src/buildtool/execution_api/local/local_response.hpp
index 3cc04361..141ffbe3 100644
--- a/src/buildtool/execution_api/local/local_response.hpp
+++ b/src/buildtool/execution_api/local/local_response.hpp
@@ -16,9 +16,11 @@
 #define INCLUDED_SRC_BUILDTOOL_EXECUTION_API_LOCAL_LOCAL_RESPONSE_HPP
 
 #include <cstddef>
+#include <optional>
 #include <string>
 #include <utility>
 
+#include "fmt/core.h"
 #include "gsl/gsl"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
 #include "src/buildtool/crypto/hash_function.hpp"
@@ -28,6 +30,7 @@
 #include "src/buildtool/logging/log_level.hpp"
 #include "src/buildtool/logging/logger.hpp"
 #include "src/buildtool/storage/storage.hpp"
+#include "src/utils/cpp/expected.hpp"
 
 /// \brief Response of a LocalAction.
 class LocalResponse final : public IExecutionResponse {
@@ -66,14 +69,22 @@ class LocalResponse final : public IExecutionResponse {
         return action_id_;
     }
 
-    auto Artifacts() noexcept -> ArtifactInfos const& final {
-        Populate();
-        return artifacts_;
+    auto Artifacts() noexcept
+        -> expected<gsl::not_null<ArtifactInfos const*>, std::string> final {
+        if (auto error_msg = Populate()) {
+            return unexpected{*std::move(error_msg)};
+        }
+        return gsl::not_null<ArtifactInfos const*>(
+            &artifacts_);  // explicit type needed for expected
     }
 
-    auto DirectorySymlinks() noexcept -> DirSymlinks const& final {
-        Populate();
-        return dir_symlinks_;
+    auto DirectorySymlinks() noexcept
+        -> expected<gsl::not_null<DirSymlinks const*>, std::string> final {
+        if (auto error_msg = Populate()) {
+            return unexpected{*std::move(error_msg)};
+        }
+        return gsl::not_null<DirSymlinks const*>(
+            &dir_symlinks_);  // explicit type needed for expected
     }
 
   private:
@@ -92,10 +103,12 @@ class LocalResponse final : public IExecutionResponse {
           output_{std::move(output)},
           storage_{*storage} {}
 
-    void Populate() noexcept {
+    /// \brief Populates the stored data, once.
+    /// \returns Error message on failure, nullopt on success.
+    [[nodiscard]] auto Populate() noexcept -> std::optional<std::string> {
         // Initialized only once lazily
         if (populated_) {
-            return;
+            return std::nullopt;
         }
         populated_ = true;
 
@@ -119,7 +132,9 @@ class LocalResponse final : public IExecutionResponse {
             auto digest =
                 ArtifactDigestFactory::FromBazel(hash_type, file.digest());
             if (not digest) {
-                return;
+                return fmt::format(
+                    "LocalResponse: failed to create artifact digest for {}",
+                    file.path());
             }
             try {
                 artifacts.emplace(
@@ -128,8 +143,12 @@ class LocalResponse final : public IExecutionResponse {
                                          .type = file.is_executable()
                                                      ? ObjectType::Executable
                                                      : ObjectType::File});
-            } catch (...) {
-                return;
+            } catch (std::exception const& ex) {
+                return fmt::format(
+                    "LocalResponse: unexpected failure gathering digest for "
+                    "{}:\n{}",
+                    file.path(),
+                    ex.what());
             }
         }
 
@@ -143,8 +162,12 @@ class LocalResponse final : public IExecutionResponse {
                             ArtifactDigestFactory::HashDataAs<ObjectType::File>(
                                 storage_.GetHashFunction(), link.target()),
                         .type = ObjectType::Symlink});
-            } catch (...) {
-                return;
+            } catch (std::exception const& ex) {
+                return fmt::format(
+                    "LocalResponse: unexpected failure gathering digest for "
+                    "{}:\n{}",
+                    link.path(),
+                    ex.what());
             }
         }
         for (auto const& link : action_result.output_directory_symlinks()) {
@@ -157,8 +180,12 @@ class LocalResponse final : public IExecutionResponse {
                                 storage_.GetHashFunction(), link.target()),
                         .type = ObjectType::Symlink});
                 dir_symlinks.emplace(link.path());  // add it to set
-            } catch (...) {
-                return;
+            } catch (std::exception const& ex) {
+                return fmt::format(
+                    "LocalResponse: unexpected failure gathering digest for "
+                    "{}:\n{}",
+                    link.path(),
+                    ex.what());
             }
         }
 
@@ -167,19 +194,26 @@ class LocalResponse final : public IExecutionResponse {
             auto digest =
                 ArtifactDigestFactory::FromBazel(hash_type, dir.tree_digest());
             if (not digest) {
-                return;
+                return fmt::format(
+                    "LocalResponse: failed to create artifact digest for {}",
+                    dir.path());
             }
             try {
                 artifacts.emplace(
                     dir.path(),
                     Artifact::ObjectInfo{.digest = *std::move(digest),
                                          .type = ObjectType::Tree});
-            } catch (...) {
-                return;
+            } catch (std::exception const& ex) {
+                return fmt::format(
+                    "LocalResponse: unexpected failure gathering digest for "
+                    "{}:\n{}",
+                    dir.path(),
+                    ex.what());
             }
         }
         artifacts_ = std::move(artifacts);
         dir_symlinks_ = std::move(dir_symlinks);
+        return std::nullopt;
     }
 
     [[nodiscard]] auto ReadContent(bazel_re::Digest const& digest)
diff --git a/src/buildtool/execution_api/remote/TARGETS b/src/buildtool/execution_api/remote/TARGETS
index ae67146d..ee1de5cb 100644
--- a/src/buildtool/execution_api/remote/TARGETS
+++ b/src/buildtool/execution_api/remote/TARGETS
@@ -34,6 +34,7 @@
     , ["src/buildtool/execution_api/bazel_msg", "bazel_msg_factory"]
     , ["src/buildtool/auth", "auth"]
     , ["src/buildtool/execution_api/common", "bytestream-common"]
+    , ["src/utils/cpp", "expected"]
     , ["src/utils/cpp", "gsl"]
     , ["src/buildtool/common/remote", "client_common"]
     , ["src/buildtool/common/remote", "port"]
@@ -48,7 +49,8 @@
     ]
   , "stage": ["src", "buildtool", "execution_api", "remote"]
   , "private-deps":
-    [ ["src/buildtool/common", "artifact_digest_factory"]
+    [ ["@", "fmt", "", "fmt"]
+    , ["src/buildtool/common", "artifact_digest_factory"]
     , ["src/buildtool/common", "bazel_digest_factory"]
     , ["src/buildtool/common", "protocol_traits"]
     , ["src/buildtool/file_system", "file_system_manager"]
diff --git a/src/buildtool/execution_api/remote/bazel/bazel_response.cpp b/src/buildtool/execution_api/remote/bazel/bazel_response.cpp
index c536f5dd..468a2531 100644
--- a/src/buildtool/execution_api/remote/bazel/bazel_response.cpp
+++ b/src/buildtool/execution_api/remote/bazel/bazel_response.cpp
@@ -17,7 +17,7 @@
 #include <cstddef>
 #include <functional>
 
-#include "gsl/gsl"
+#include "fmt/core.h"
 #include "src/buildtool/common/artifact_digest.hpp"
 #include "src/buildtool/common/artifact_digest_factory.hpp"
 #include "src/buildtool/common/bazel_digest_factory.hpp"
@@ -56,20 +56,28 @@ auto BazelResponse::ReadStringBlob(bazel_re::Digest const& id) noexcept
     return std::string{};
 }
 
-auto BazelResponse::Artifacts() noexcept -> ArtifactInfos const& {
-    Populate();
-    return artifacts_;
+auto BazelResponse::Artifacts() noexcept
+    -> expected<gsl::not_null<ArtifactInfos const*>, std::string> {
+    if (auto error_msg = Populate()) {
+        return unexpected{*std::move(error_msg)};
+    }
+    return gsl::not_null<ArtifactInfos const*>(
+        &artifacts_);  // explicit type needed for expected
 }
 
-auto BazelResponse::DirectorySymlinks() noexcept -> DirSymlinks const& {
-    Populate();
-    return dir_symlinks_;
+auto BazelResponse::DirectorySymlinks() noexcept
+    -> expected<gsl::not_null<DirSymlinks const*>, std::string> {
+    if (auto error_msg = Populate()) {
+        return unexpected{*std::move(error_msg)};
+    }
+    return gsl::not_null<DirSymlinks const*>(
+        &dir_symlinks_);  // explicit type needed for expected
 }
 
-void BazelResponse::Populate() noexcept {
+auto BazelResponse::Populate() noexcept -> std::optional<std::string> {
     // Initialized only once lazily
     if (populated_) {
-        return;
+        return std::nullopt;
     }
     populated_ = true;
 
@@ -92,7 +100,9 @@ void BazelResponse::Populate() noexcept {
         auto digest =
             ArtifactDigestFactory::FromBazel(hash_type, file.digest());
         if (not digest) {
-            return;
+            return fmt::format(
+                "BazelResponse: failed to create artifact digest for {}",
+                file.path());
         }
         try {
             artifacts.emplace(
@@ -101,8 +111,12 @@ void BazelResponse::Populate() noexcept {
                                      .type = file.is_executable()
                                                  ? ObjectType::Executable
                                                  : ObjectType::File});
-        } catch (...) {
-            return;
+        } catch (std::exception const& ex) {
+            return fmt::format(
+                "BazelResponse: unexpected failure gathering digest for "
+                "{}:\n{}",
+                file.path(),
+                ex.what());
         }
     }
 
@@ -116,8 +130,12 @@ void BazelResponse::Populate() noexcept {
                         ArtifactDigestFactory::HashDataAs<ObjectType::File>(
                             network_->GetHashFunction(), link.target()),
                     .type = ObjectType::Symlink});
-        } catch (...) {
-            return;
+        } catch (std::exception const& ex) {
+            return fmt::format(
+                "BazelResponse: unexpected failure gathering digest for "
+                "{}:\n{}",
+                link.path(),
+                ex.what());
         }
     }
     for (auto const& link : action_result.output_directory_symlinks()) {
@@ -130,8 +148,12 @@ void BazelResponse::Populate() noexcept {
                             network_->GetHashFunction(), link.target()),
                     .type = ObjectType::Symlink});
             dir_symlinks.emplace(link.path());  // add it to set
-        } catch (...) {
-            return;
+        } catch (std::exception const& ex) {
+            return fmt::format(
+                "BazelResponse: unexpected failure gathering digest for "
+                "{}:\n{}",
+                link.path(),
+                ex.what());
         }
     }
 
@@ -141,7 +163,9 @@ void BazelResponse::Populate() noexcept {
             auto digest =
                 ArtifactDigestFactory::FromBazel(hash_type, tree.tree_digest());
             if (not digest) {
-                return;
+                return fmt::format(
+                    "BazelResponse: failed to create artifact digest for {}",
+                    tree.path());
             }
             ExpectsAudit(digest->IsTree());
             try {
@@ -149,13 +173,17 @@ void BazelResponse::Populate() noexcept {
                     tree.path(),
                     Artifact::ObjectInfo{.digest = *std::move(digest),
                                          .type = ObjectType::Tree});
-            } catch (...) {
-                return;
+            } catch (std::exception const& ex) {
+                return fmt::format(
+                    "BazelResponse: unexpected failure gathering digest for "
+                    "{}:\n{}",
+                    tree.path(),
+                    ex.what());
             }
         }
         artifacts_ = std::move(artifacts);
         dir_symlinks_ = std::move(dir_symlinks);
-        return;
+        return std::nullopt;
     }
 
     // obtain tree digests for output directories
@@ -176,7 +204,9 @@ void BazelResponse::Populate() noexcept {
                 auto tree = BazelMsgFactory::MessageFromString<bazel_re::Tree>(
                     *tree_blob.data);
                 if (not tree) {
-                    return;
+                    return fmt::format(
+                        "BazelResponse: failed to create Tree for {}",
+                        tree_blob.digest.hash());
                 }
 
                 // The server does not store the Directory messages it just
@@ -185,22 +215,30 @@ void BazelResponse::Populate() noexcept {
                 // have to upload them manually.
                 auto root_digest = UploadTreeMessageDirectories(*tree);
                 if (not root_digest) {
-                    Logger::Log(LogLevel::Error,
-                                "uploading Tree's Directory messages failed");
-                    return;
+                    auto const error = fmt::format(
+                        "BazelResponse: failure in uploading Tree Directory "
+                        "message for {}",
+                        tree_blob.digest.hash());
+                    Logger::Log(LogLevel::Trace, error);
+                    return error;
                 }
                 artifacts.emplace(
                     action_result.output_directories(pos).path(),
                     Artifact::ObjectInfo{.digest = *root_digest,
                                          .type = ObjectType::Tree});
-            } catch (...) {
-                return;
+            } catch (std::exception const& ex) {
+                return fmt::format(
+                    "BazelResponse: unexpected failure gathering digest for "
+                    "{}:\n{}",
+                    tree_blob.digest.hash(),
+                    ex.what());
             }
             ++pos;
         }
     }
     artifacts_ = std::move(artifacts);
     dir_symlinks_ = std::move(dir_symlinks);
+    return std::nullopt;
 }
 
 auto BazelResponse::UploadTreeMessageDirectories(
diff --git a/src/buildtool/execution_api/remote/bazel/bazel_response.hpp b/src/buildtool/execution_api/remote/bazel/bazel_response.hpp
index 6e37d344..ec3e9748 100644
--- a/src/buildtool/execution_api/remote/bazel/bazel_response.hpp
+++ b/src/buildtool/execution_api/remote/bazel/bazel_response.hpp
@@ -20,9 +20,11 @@
 #include <utility>  // std::move
 #include <vector>
 
+#include "gsl/gsl"
 #include "src/buildtool/execution_api/common/execution_api.hpp"
 #include "src/buildtool/execution_api/remote/bazel/bazel_execution_client.hpp"
 #include "src/buildtool/execution_api/remote/bazel/bazel_network.hpp"
+#include "src/utils/cpp/expected.hpp"
 
 class BazelAction;
 
@@ -58,8 +60,10 @@ class BazelResponse final : public IExecutionResponse {
         return action_id_;
     }
 
-    auto Artifacts() noexcept -> ArtifactInfos const& final;
-    auto DirectorySymlinks() noexcept -> DirSymlinks const& final;
+    auto Artifacts() noexcept
+        -> expected<gsl::not_null<ArtifactInfos const*>, std::string> final;
+    auto DirectorySymlinks() noexcept
+        -> expected<gsl::not_null<DirSymlinks const*>, std::string> final;
 
   private:
     std::string action_id_{};
@@ -84,7 +88,9 @@ class BazelResponse final : public IExecutionResponse {
         return id.size_bytes() != 0;
     }
 
-    void Populate() noexcept;
+    /// \brief Populates the stored data, once.
+    /// \returns Error message on failure, nullopt on success.
+    [[nodiscard]] auto Populate() noexcept -> std::optional<std::string>;
 
     [[nodiscard]] auto UploadTreeMessageDirectories(
         bazel_re::Tree const& tree) const -> std::optional<ArtifactDigest>;