feat(cli): Get StackOutputs in CDK application

[rcollette]

Use Case

I have an output

const output = new CfnOutput(this, 'BastionPublicIP', {
            exportName: 'bastion-public-ip',
            value: bastion.instancePublicIp,
            description: 'The public IP address of the bastion host'
        });

And I want a simple way where I can console out a message to the user for how to to connect to the bastion host, without having to write another shell script or application that has to parse the output json file.

console.log('Use the following ssh command to connect to the bastion host:');
console.log(`ssh ec2-user@${output.value}`)

Proposed Solution

Unfortunately, I am not aware of the internals of the cli, but it would seem like perhaps some form of protected callback method in the Stack or App might be provided.

There is Stack.resolve() but the documentation isn't clear as to what scenario it is used for.

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This is a 🚀 Feature Request

[shivlaks]

@rcollette I think what you're touching on is the programmatic usage of the CLI which would enable you to easily deploy stacks, write outputs wherever you would want with the instructions you want to share with the user.

Right now deploy will finish deploying all the stacks that were specified and the outputs will be written to a file (if specified) and console. The simplest way today would be to read that output file, which would be keyed under your stack name and print it out.

Out of curiosity, where would you want to be able to print your instructions out and how do you deploy your stacks today?

[rcollette]

For something like deploying a bastion host, the user would run a CDK application. I am aware of the JSON output, but that requires launching a separate application since, unless I am unaware, there is no callback when the CLI has completed performing a deployment.

If there was some application callback method when deployment completes, then I could parse the json file in the same CDK application and write to the console, but it would seem more effective to return the same json data to that callback method, perhaps in a more general context object, allowing other completion data to be added as needed in the future (ex. a model of the stack current state?)

[iDVB]

@shivlaks We would also love some way to hook into a "Post Deploy" step of the CLI.
Programmatic access to the CLI would be great... or some kind of Plugins API?

In Serverless Framework this can be done a number of ways or even building a custom plugin that can hook into various steps of the build and deploy process.

Our usecase is that we currently have SLS exporting a whitelist of CFN outputs as well as some custom ones stored statically in yaml... to a .env file which can then be baked into our frontend code buy most frameworks (CreateReactApp, GatsbyJS, NextJS etc.) Things like API endpoints etc.

Having plugin or programmatic access is required (beyond --outputs-file) as the above frameworks require prefexes on all things in the .env file. (eg. GATSBY_XXXX)

Doing this with SLS looks like this...
sls deploy > .env > gatsby build > fin

Doing this with CDK today looks like this...
CUSTOM_ENVS=blah make deploy > cdk deploy --outputs-file outputs.json > node out2env.js > .env > gatsby build > fin

Reallllly would love plugin or programmatic CLI support to wrap CDK is super warm fussy helpers so that frontend devs love CDK too.