merge.jsonnet

// extensible takes a jsonnet value and if it's an object it recursively
// computes a version of the object where each of its fields is converted
// to the "+:" form.
local extensible(o) = if std.isObject(o) then {
  [n]+: extensible(o[n])
  for n in std.objectFields(o)
} else o;

// merge takes two objects and merges them recursively.
local merge(a, b) = a + extensible(b);

local testCases = [
  [
    {
      a: 1,
    },
    {
      b: 2,
    },
    {
      a: 1,
      b: 2,
    },
  ],
  [
    {
      x: {
        a: 1,
      },
    },
    {
      x: {
        b: 2,
      },
    },
    {
      x: {
        a: 1,
        b: 2,
      },
    },
  ],
];

local check = [
  std.assertEqual(merge(e[0], e[1]), e[2])
  for e in testCases
];

check