Overwrite a nested list element using jsonnet - json

Question

I have the following json
{
"namespace": "monitoring",
"name": "alok",
"spec": {
"replicas": 1,
"template": {
"metadata": "aaa",
"spec": {
"containers": [
{
"image": "practodev/test:test",
"env": [
{
"name":"GF_SERVER_HTTP_PORT",
"value":"3000"
},
{
"name":"GF_SERVER_HTTPS_PORT",
"value":"443"
},
]
}
]
}
}
}
}
How do I add deployment_env.json using jsonnet?
{
"env": [
{
"name":"GF_AUTH_DISABLE_LOGIN_FORM",
"value":"false"
},
{
"name":"GF_AUTH_BASIC_ENABLED",
"value":"false"
},
]
}
I need to add it under spec.template.containers[0].env = deployment_env.json
I wrote the below jsonnet to do that. It appends a new element. But i need to change the existing 0th container element in the json. Please suggest how to do it.
local grafana_envs = (import 'custom_grafana/deployment_env.json');
local grafanaDeployment = (import 'nested.json') + {
spec+: {
template+: {
spec+: {
containers+: [{
envs: grafana_envs.env,
}]
}
}
},
};
grafanaDeployment

Answer 1

See below for an implementation that allows adding env to an existing container by its index in the containers[] array.
Do note that jsonnet is much better suited to work with objects (i.e. dictionaries / maps) rather than arrays, thus it needs contrived handling via std.mapWithIndex(), to be able to modify an entry from its matching index.
local grafana_envs = (import 'deployment_env.json');
// Add extra_env to a container by its idx passed containers array
local override_env(containers, idx, extra_env) = (
local f(i, x) = (
if i == idx then x {env+: extra_env} else x
);
std.mapWithIndex(f, containers)
);
local grafanaDeployment = (import 'nested.json') + {
spec+: {
template+: {
spec+: {
containers: override_env(super.containers, 0, grafana_envs.env)
}
}
},
};
grafanaDeployment

Answer 2

Alternative implementation, not relying on the array index position, but image value instead (which makes more sense here as the env must be understood by the image implementation)
local grafana_envs = (import 'deployment_env.json');
local TARGET_CONTAINER_IMAGE = 'practodev/test:test';
local grafanaDeployment = (import 'nested.json') + {
spec+: {
template+: {
spec+: {
containers: [
// TARGET_CONTAINER_IMAGE identifies which container to modify
if x.image == TARGET_CONTAINER_IMAGE
then x { env+: grafana_envs.env }
else x
for x in super.containers
],
},
},
},
};
grafanaDeployment

Answer 3

An alternative to std.mapWithIndex is to explicitly iterate through the indexes based on the size of the list.
local grafana_envs = (import 'deployment_env.json');
local grafanaDeployment = (import 'nested.json') + {
spec+: {
template+: {
spec+: {
containers:
[super.containers[0] { env+: grafana_envs.env }]
+
[
super.containers[i]
for i in std.range(1, std.length(super.containers) - 1)
]
}
}
},
};
grafanaDeployment
If one needed to modify a specific index other than 0, say 5, then they could do so by putting an if i == 5 in the loop.