How to add a [key: alias] node to a map?

[slhck]

I have a map and, somewhere else, I have some anchors defined.

I would like to change the name of an anchor, then change the alias that references it to use new name. This works.

But I would like to also add a new entry to the map, and make it reference that anchor.

Here is what I have so far:

import YAML, { isAlias, isMap } from "yaml";

const TEST_YAML_STRING = `
my_custom_schedules:
  custom_schedule: &custom_schedule_alias
    foo: bar

my_config:
  default: &default
    foo: baz
  my-c-005: *default
  my-c-006: *custom_schedule_alias
`;

const document = YAML.parseDocument(TEST_YAML_STRING);
const customSchedules = document.get("my_custom_schedules");
if (isMap(customSchedules)) {
  const customSchedule = customSchedules.get("custom_schedule");
  if (isMap(customSchedule)) {
    // change the name of the anchor
    customSchedule.anchor = "new_custom_schedule_anchor";
  }
}

const config = document.get("my_config");
if (isMap(config)) {
  // change the existing C006 alias to point to the new anchor
  const myC006 = config.get("my-c-006");
  if (isAlias(myC006)) {
    myC006.source = "new_custom_schedule_anchor";
  }

  // create a new alias for C007 to point to the anchor
  config.add({ key: "my-c-007", value: "???" });
}

const documentStr = document.toString();

I would expect the following:

my_custom_schedules:
  custom_schedule: &new_custom_schedule_anchor
    foo: bar

my_config:
  default: &default
    foo: baz
  my-c-005: *default
  my-c-006: *new_custom_schedule_anchor
  my-c-007: *new_custom_schedule_anchor

But how do I add my-c-007 with the correct alias?

[eemeli]

I'd use a visitor. Something like this ought to work, though I've not tested it:

import { type Document, visit } from 'yaml'

function renameAlias(doc: Document, prev: string, next: string) {
  visit(doc, {
    Alias(_, alias) {
      if (alias.source === prev) alias.source = next
    },
    Node(_, node) {
      if (node.anchor === prev) node.anchor = next
    }
  )}
}

[slhck]

Thanks for the suggestion, but I think that's not what I need. I know how to rename the alias. I would like to add a new one in the map. .add() does not seem to work, as it requires a key/value, no?

[eemeli]

Use doc.createAlias(): https://eemeli.org/yaml/#creating-nodes

[slhck]

Thanks, I figured that I'd need it, but the exact steps required weren't obvious for me from the given examples.

After fumbling around a lot, here is the simplest way I found to create a new alias:

const document = YAML.parseDocument('foo: bar');
const foo = document.get('foo', true);

if (isScalar(foo)) {
  foo.anchor = 'foo_anchor';
  const alias = document.createAlias(foo);
  document.add({ key: 'foo_alias', value: alias });
}

expect(document.toString()).toContain('foo: &foo_anchor');
expect(document.toString()).toContain('foo_alias: *foo_anchor');

Here is the fully working example from the original question — note that I forced casts of the return values from .get which is not recommended, but I am validating my schema beforehand, so I know the values are there:

const TEST_YAML_STRING = `
my_custom_schedules:
  custom_schedule: &custom_schedule_alias
    foo: bar

my_config:
  default: &default
    foo: baz
  my-c-005: *default
  my-c-006: *custom_schedule_alias
`;

const document = YAML.parseDocument(TEST_YAML_STRING);
const customSchedules = document.get("my_custom_schedules") as YAMLMap;
const customSchedule = customSchedules.get("custom_schedule") as YAMLMap;
customSchedule.anchor = "new_custom_schedule_anchor";

const config = document.get("my_config") as YAMLMap;
// change the existing C006 alias to point to the new anchor
const myC006 = config.get("my-c-006") as Alias;
myC006.source = "new_custom_schedule_anchor";

// create a new alias for C007
config.add({
  key: "my-c-007",
  value: document.createAlias(customSchedule),
});

const documentStr = document.toString();
expect(documentStr).toContain("custom_schedule: &new_custom_schedule_anchor");
expect(documentStr).toContain("my-c-006: *new_custom_schedule_anchor");
expect(documentStr).toContain("my-c-007: *new_custom_schedule_anchor");