Bug when handling assert statements

[mgyucht]

Discovered the following behavior difference between sjsonnet and jsonnet.

test.jsonnet:

// Returns true if any key from base is overridden in object
local isAnyKeyOverridden = function (base, object)
  local keys = std.objectFields(base);
  std.foldl(function(acc, field) acc || base[field] != object[field], keys, false);

local base = {
  paramA: null,
  paramB: null,
};

base + {
  assert !isAnyKeyOverridden(base, $),
}

test2.jsonnet:

local base = import "test.jsonnet";
local Parameterized = base + { paramA:: 3 };
Parameterized

Output from jsonnet test2.jsonnet:

RUNTIME ERROR: Object assertion failed.
        ../universe/test.jsonnet:12:10-38       thunk <object_assert>
        During manifestation

Output from sjsonnet test2.jsonnet:

{
   "paramB": null
}

[rschatz]

I think I have also run into this bug, and I have found a simpler reproducer:

{ } + {
    assert false
}

With jsonnet this fails, with sjsonnet it just returns { }.

Apparently, when combining objects, it's ignoring assertions from the second object. Putting the assertion in the first object makes it fail as expected.

In the original bug report, if you switch the + around, it also fails as expected:

{
  assert !isAnyKeyOverridden(base, $),
} + base