Exporting config w/ arrays in new platform plugin breaks

[jloleysens]

Kibana version:

Master since at least 4ca2fbdb11

Describe the bug:

Given a config object like:

const configSchema = schema.object(
  {
    enabled: schema.boolean({ defaultValue: true }),
    proxyFilter: schema.arrayOf(schema.string(), { defaultValue: ['.*'] }),
    ssl: schema.object({ verify: schema.boolean({ defaultValue: false }) }, {}),

    // This does not actually work
    proxyConfig: schema.arrayOf(
      schema.object({
        match: schema.object({
          protocol: schema.string({ defaultValue: '*' }),
          host: schema.string({ defaultValue: '*' }),
          port: schema.string({ defaultValue: '*' }),
          path: schema.string({ defaultValue: '*' }),
        }),

        timeout: schema.number(),
        ssl: schema.object(
          {
            verify: schema.boolean(),
            ca: schema.arrayOf(schema.string()),
            cert: schema.string(),
            key: schema.string(),
          },
          { defaultValue: undefined }
        ),
      }),
      { defaultValue: [] }
    ),
  },
  { defaultValue: undefined }
)

Kibana fails to start when setting a proxyConfig like (2nd item not needed, just illustrating array) inside kibana.yml:

console.proxyConfig:
    - timeout: 20
      ssl:
        cert: ''
        ca:
          - bla
        verify: true
        key: ''
    - timeout: 20
      ssl:
        cert: ''
        ca:
          - bla
        verify: true
        key: ''

Error: Error: Unknown configuration key(s): "console.proxyConfig". Check for spelling errors and ensure that expected plugins are installed

Expected behavior:

Kibana should start as normal and provide config to the plugin. Validation of the object seems to be working.

Any additional context:

Looks like this is caused by this line:

kibana/src/core/server/legacy/config/get_unused_config_keys.ts

Line 62 in 320b608

const inputKeys = getFlattenedKeys(settings);

Returning a value like console.proxyConfig and then attempting to match against what it considers root paths like console.proxyConfig.0.timeout (the latter is not a subset of the former).

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[pgayvallet]

The way we flatten paths for the config's getUsedPaths considers arrays as objects, and therefor flatten the underneath keys.

kibana/src/core/server/config/object_to_config_adapter.ts

Lines 52 to 64 in 6034cc7

	function* flattenObjectKeys(
	obj: { [key: string]: any },
	path: string = ''
	): IterableIterator<string> {
	if (typeof obj !== 'object' || obj === null) {
	yield path;
	} else {
	for (const [key, value] of Object.entries(obj)) {
	const newPath = path !== '' ? `${path}.${key}` : key;
	yield* flattenObjectKeys(value, newPath);
	}
	}
	}

{a: [1, 2]} will flattenKey to ['a.0', 'a.1']

This is a difference with how the other parts of core (and legacy) was doing it, which preserves arrays at final values

kibana/src/core/utils/get_flattened_object.ts

Lines 24 to 36 in 133c299

	/**
	* Flattens a deeply nested object to a map of dot-separated
	* paths pointing to all primitive values **and arrays**
	* from `rootValue`.
	*
	* example:
	* getFlattenedObject({ a: { b: 1, c: [2,3] } })
	* // => { 'a.b': 1, 'a.c': [2,3] }
	*
	* @param {Object} rootValue
	* @returns {Object}
	*/
	export function getFlattenedObject(rootValue: Record<string, any>) {

{a: [1, 2]} will flattenKey to ['a']

I think considering arrays as terminal values makes sense, and would fix this issue.

@restrry do you see any reason not to do this change?

[pgayvallet]

Created #56105