Example of merge operation in helm

Question

In offcial documentaion the description is very poor:

Merge two or more dictionaries into one, giving precedence to the dest dictionary:

$newdict := merge $dest $source1 $source2 This is a deep merge operation but not a deep copy operation. Nested objects that are merged are the same instance on both dicts. If you want a deep copy along with the merge, then use the deepCopy function along with merging...

Could you please provide example with input and output values ?

Answer 1

Consider we have 3 maps (or Dict) as follows:

dst = {
    "default": "default",
    "overwrite": "me",
    "key": "true"
}
src1 = {
    "overwrite": "overwritten",
    "key": "false",
    "name": "value1"
}
src2 = {
    "key": "false",
    "name": "value2"
}

You can represent it in helm with:

{{ $dst := dict "default" "default" "overwrite" "me" "key" "true"}}
{{ $src1 := dict "overwrite" "overwritten" "key" "false" "name" "value1"}}
{{ $src2 := dict  "key" "false" "name" "value2"}}

Merge

In merging dicts, keys with different values will be kept, and in the same keys cases, dst dict takes precedence. For example, result of merge $dst $src1 $src2 would be:

mergedDict = {
    "default": "default",
    "key": "true",
    "name": "value1",
    "overwrite": "me"
}

or in helm syntacs:

{{ $mergedDict := merge $dst $src1 $src2 }}

would be:

mergedDict: map[default:default key:true name:value1 overwrite:me]

mergeOverwrite

In mergeOverwrite, precedence would be from right to left. So we have:

{{ $mergedDict := mergeOverwrite  $dst $src1 $src2}}

would be:

mergedDict: map[default:default key:false name:value2 overwrite:overwritten]

or

{
    "default": "default",
    "key": "false",
    "name": "value2",
    "overwrite": "overwritten"
}