Treat empty env var paths as unset

We make sure the env var paths are actually set (ie. not "") before
sending them to the canonicalization function. If we forget to do so,
the user will end up facing a puzzled failed assertion internal error.

We issue a non-failing warning as a stop-gap measure. We could want to
revisit this to issue a detailed failing error message in the future.

2 files changed, 16 insertions, 0 deletions

diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 885bae69c..5377f093b 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -54,6 +54,18 @@ std::optional<std::string> getEnv(const std::string & key)
     return std::string(value);
 }
 
+std::optional<std::string> getEnvNonEmpty(const std::string & key) {
+    auto value = getEnv(key);
+    if (value == "") {
+        // TODO: determine whether this should be a warning or an error.
+        logWarning({
+                .msg = hintfmt("ignoring the '%1%' env variable, its value has been set to \"\"", key)
+         });
+        return std::nullopt;
+    } else {
+        return value;
+    }
+}
 
 std::map<std::string, std::string> getEnv()
 {
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index b5625ecef..3293c758f 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -39,6 +39,10 @@ extern const std::string nativeSystem;
 /* Return an environment variable. */
 std::optional<std::string> getEnv(const std::string & key);
 
+/* Return a non empty environment variable. Returns nullopt if the env
+variable is set to "" */
+std::optional<std::string> getEnvNonEmpty(const std::string & key);
+
 /* Get the entire environment. */
 std::map<std::string, std::string> getEnv();