Invocation logging: add new field context variables

It allows to specify a list of environment variables, which are captured at
invocation time and stored as key-value pairs in the metadata file. This allows
to get some information about the invocation context such as username,
merge-request ID or source branch (on a CI runner), or others.

3 files changed, 20 insertions, 0 deletions

diff --git a/src/other_tools/just_mr/cli.hpp b/src/other_tools/just_mr/cli.hpp
index d8ad0366..df952957 100644
--- a/src/other_tools/just_mr/cli.hpp
+++ b/src/other_tools/just_mr/cli.hpp
@@ -93,6 +93,7 @@ struct MultiRepoGcArguments {
 struct InvocationLogArguments {
     std::optional<std::filesystem::path> directory{std::nullopt};
     std::optional<std::string> invocation_msg{std::nullopt};
+    std::vector<std::string> context_vars{};
     std::optional<std::string> project_id{std::nullopt};
     std::optional<std::string> metadata{std::nullopt};
     std::optional<std::string> graph_file{std::nullopt};
diff --git a/src/other_tools/just_mr/launch.cpp b/src/other_tools/just_mr/launch.cpp
index ca21e268..dc861c11 100644
--- a/src/other_tools/just_mr/launch.cpp
+++ b/src/other_tools/just_mr/launch.cpp
@@ -371,6 +371,15 @@ auto CallJust(std::optional<std::filesystem::path> const& config_file,
             meta["configuration"] = mr_config_pair->second;
         }
         meta["cmdline"] = cmd;
+        if (not invocation_log.context_vars.empty()) {
+            auto context = nlohmann::json::object();
+            for (auto const& env_var : invocation_log.context_vars) {
+                auto* env_value = std::getenv(env_var.c_str());
+                context[env_var] =
+                    env_value != nullptr ? env_value : nlohmann::json{};
+            }
+            meta["context"] = context;
+        }
         // "configuration" -- the blob-identifier of the multi-repo
         // configuration
         auto file_name = *log_dir / *invocation_log.metadata;
diff --git a/src/other_tools/just_mr/rc.cpp b/src/other_tools/just_mr/rc.cpp
index 51813dfb..7d7f6f5a 100644
--- a/src/other_tools/just_mr/rc.cpp
+++ b/src/other_tools/just_mr/rc.cpp
@@ -635,6 +635,16 @@ namespace {
             if (msg->IsString()) {
                 clargs->invocation_log.invocation_msg = msg->String();
             }
+            auto context_vars =
+                invocation_log->Get("context variables", Expression::none_t{});
+            if (context_vars->IsList()) {
+                for (auto const& env_var : context_vars->List()) {
+                    if (env_var->IsString()) {
+                        clargs->invocation_log.context_vars.emplace_back(
+                            env_var->String());
+                    }
+                }
+            }
         }
     }
     // read config lookup order