Before this change, expressions like:
with import <nixpkgs> {};
runCommand "foo" {} ''
echo '@nix {}' >&$NIX_LOG_FD
''
would result in Lix crashing, because accessing nonexistent fields of
a JSON object throws an exception.
Rather than handling each field individually, we just catch JSON
exceptions wholesale. Since these log messages are an unusual
circumstance, log a warning when this happens.
Fixes#544.
Change-Id: Idc2d8acf6e37046b3ec212f42e29269163dca893
Linus Heckemann
e55cd3beea