refactor(tvix): getEnv(): Return std::optional r/1756

This allows distinguishing between an empty value and no value.

Patch ported from upstream at
https://github.com/NixOS/nix/commit/ba87b08f8529e4d9f8c58d8c625152058ceadb75

Change-Id: I061cc8e16b1a7a0341adfc3b0edca1c0c51d5c97
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1884
Tested-by: BuildkiteCI
Reviewed-by: kanepyork <rikingcoding@gmail.com>

1 files changed, 14 insertions, 11 deletions

diff --git a/third_party/nix/src/libstore/globals.cc b/third_party/nix/src/libstore/globals.cc
index 34f5d4605bf5..6babb4589fa0 100644
--- a/third_party/nix/src/libstore/globals.cc
+++ b/third_party/nix/src/libstore/globals.cc
@@ -31,19 +31,22 @@ static GlobalConfig::Register r1(&settings);
 Settings::Settings()
     : nixPrefix(NIX_PREFIX),
       nixStore(canonPath(
-          getEnv("NIX_STORE_DIR", getEnv("NIX_STORE", NIX_STORE_DIR)))),
-      nixDataDir(canonPath(getEnv("NIX_DATA_DIR", NIX_DATA_DIR))),
-      nixLogDir(canonPath(getEnv("NIX_LOG_DIR", NIX_LOG_DIR))),
-      nixStateDir(canonPath(getEnv("NIX_STATE_DIR", NIX_STATE_DIR))),
-      nixConfDir(canonPath(getEnv("NIX_CONF_DIR", NIX_CONF_DIR))),
-      nixLibexecDir(canonPath(getEnv("NIX_LIBEXEC_DIR", NIX_LIBEXEC_DIR))),
-      nixBinDir(canonPath(getEnv("NIX_BIN_DIR", NIX_BIN_DIR))),
+          getEnv("NIX_STORE_DIR")
+              .value_or(getEnv("NIX_STORE").value_or(NIX_STORE_DIR)))),
+      nixDataDir(canonPath(getEnv("NIX_DATA_DIR").value_or(NIX_DATA_DIR))),
+      nixLogDir(canonPath(getEnv("NIX_LOG_DIR").value_or(NIX_LOG_DIR))),
+      nixStateDir(canonPath(getEnv("NIX_STATE_DIR").value_or(NIX_STATE_DIR))),
+      nixConfDir(canonPath(getEnv("NIX_CONF_DIR").value_or(NIX_CONF_DIR))),
+      nixLibexecDir(
+          canonPath(getEnv("NIX_LIBEXEC_DIR").value_or(NIX_LIBEXEC_DIR))),
+      nixBinDir(canonPath(getEnv("NIX_BIN_DIR").value_or(NIX_BIN_DIR))),
       nixManDir(canonPath(NIX_MAN_DIR)),
       nixDaemonSocketFile(canonPath(nixStateDir + DEFAULT_SOCKET_PATH)) {
   buildUsersGroup = getuid() == 0 ? "nixbld" : "";
-  lockCPU = getEnv("NIX_AFFINITY_HACK", "1") == "1";
+  lockCPU = getEnv("NIX_AFFINITY_HACK").value_or("1") == "1";
 
-  caFile = getEnv("NIX_SSL_CERT_FILE", getEnv("SSL_CERT_FILE", ""));
+  caFile = getEnv("NIX_SSL_CERT_FILE")
+               .value_or(getEnv("SSL_CERT_FILE").value_or(""));
   if (caFile.empty()) {
     for (auto& fn :
          {"/etc/ssl/certs/ca-certificates.crt",
@@ -58,9 +61,9 @@ Settings::Settings()
   /* Backwards compatibility. */
   // TODO(tazjin): still?
   auto s = getEnv("NIX_REMOTE_SYSTEMS");
-  if (!s.empty()) {
+  if (s) {
     Strings ss;
-    for (auto p : absl::StrSplit(s, absl::ByChar(':'), absl::SkipEmpty())) {
+    for (auto p : absl::StrSplit(*s, absl::ByChar(':'), absl::SkipEmpty())) {
       ss.push_back(absl::StrCat("@", p));
     }
     builders = concatStringsSep(" ", ss);