GraphQL - Subscription Endpoint not being Interpolated

[steve-gray]

Issue workflow progress

Progress of the issue based on the
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• 1. The issue provides a reproduction available on
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Please make sure Mesh package versions under package.json matches yours.

• 2. A failing test has been provided
• 3. A local solution has been provided
• 4. A pull request is pending review

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Describe the bug

The endpoint in the .meshrc.yaml file does not get environment variables interpolated, causing Websocket / Websocket legacy requests to fail where the URL is specified in this way. The URL is interpolated correctly when doing schema fetching and for non-subscription queries, but does not get interpolated before being passed to the websocket drivers (both legacy WS and WS), causing requests to fail.

To Reproduce Steps to reproduce the behavior:

• Use an environment variable to specify the GraphQL handler endpoint
• Try to subscribe to data.

The issue applies both when using a single endpoint and when using a dedicated subscriptionEndpoint.

Expected behavior

Should be interpolated correctly with environment variables and other tokens, and allow this.

Additional context

Was the root problem that led to me reporting #5402

[ardatan]

Fixed in e4f94eb