Add a --dry-run switch or equivalent to prefect deploy

[tjordahl]

Describe the current behavior

My continuous integration/deployment fails when there is a problem in the prefect.yaml file and I would like something to be able to validate all the entries so this can be done before the changes are merged and attempted to be deployed.

The current prefect deploy --all will deploy all flows up until it encounters an error, then stop. This leaves my Depoyments in a state of half new, half old deployments.

Describe the proposed behavior

In addition to validating the YAML schema for prefect.yaml, this should catch items such as:

• Invalid parameter values
• Incorrect endpoint specifications (missing file/function)
• Other validation

In short, everything but the POST /deployment operation. A --dry-run switch to prefect deploy would be ideal

Example Use

prefect deploy --all --dry-run

Additional context

Slack thread: https://prefect-community.slack.com/archives/CL09KU1K7/p1744654952403849
Relevant issue: #16996

[tjordahl]

Just wanted to ping on this - any plans to implement soon(ish)?
We keep getting caught with bad deployment config which leaves our server with partially updated deployments as everything above any error deploys successfully and anything below doesn't get run.

[cicdw]

We are interested in this feature but I don't have a timeline to share on when we will be able to pick it up. We would also accept a PR if you have the energy to do that!