Add parent support (devfile 2.0) to devfile

[elsony]

/kind user-story

User Story

As a devfile developer, I would like use the new devfile 2.0 support to set the parent of a devfile (devfile/api#25)

Acceptance Criteria

• If a devfile has the parent specified, load the devfile and the parent to generate a merged devfile to be used by odo
• Support the merge model defined by the devfile 2.0 specification

Links

• Related issue:

/kind user-story
/area devfile

[elsony]

@kadel I think your team has done some POC work on this before. Do you have the link to code of that POC?

[kadel]

@kadel I think your team has done some POC work on this before. Do you have the link to code of that POC?

sure

but we need to have parser in place before we can start working on this. #2918 needs to be addressed first
/status blocked

[mik-dass]

@kadel @elsony Are we planing to support kubernetes and ID parent references too?

[mik-dass]

@kadel @elsony Do we want to download the parent devfile too in the repo? Also what if the parent devfile also has a parent reference?

[girishramnani]

the parser got merged so we are unblocked

[kadel]

@kadel @elsony Are we planing to support kubernetes and ID parent references too?

Not at this time. We can consider it in the future, but there will be problems like what to do if odo is using docker mode etc... For this reason, I would defer this for now and just focus just on uri reference.

@kadel @elsony Do we want to download the parent devfile too in the repo? Also what if the parent devfile also has a parent reference?

No, we don't need to keep the parent devfile.
You can assume that parent devfile doesn't have parents.

[mik-dass]

• If schema version is V1, do nothing
• If schema version is V2, but has no parent, do nothing
• If schema version is V2 and has a parent
• Fetch the devfile without downloading, check if it the same API version or not. If not, error out.
• If no overrides are present in the local devfile, extract the components and commands from the parent devfile and append with the local one.
• If overrides are present, check the names in the local and search in the parent. If not found, error out. If found, merge the local and parent devfile and override the parent's values, maybe by using https://github.com/imdario/mergo
• Add unit and integration tests for the various above scenarios.

[neeraj-laad]

@kadel

You can assume that parent devfile doesn't have parents.

What is the rational for adding this constraint. This will become very restrictive and we'll end up with lots of copy/paste of information all over devfiles.

I think we should reconsider this.

[dharmit]

Need answers on devfile/api#25 (comment) to move further smoothly without being blocked.

[mik-dass]

https://github.com/kubernetes/apimachinery/blob/2d992b89ee6927fc5ba834371774ade243cd3732/pkg/util/strategicpatch/patch.go#L812

This function might help in merging the structs.

The directive can be added as https://github.com/kubernetes/api/blob/fd326d3007d39ad678622b2b4185892ec853aac2/core/v1/types.go#L2180.

[cdrage]

FYI / my notes, this is a good example on how a parent should be implemented / used within the Devfile: https://raw.githubusercontent.com/devfile/kubernetes-api/master/devfile-support/samples/with-nodejs-parent.devfile.yaml

schemaVersion: 2.0.0
metadata:
  name: with-parent
parent:
  uri: https://raw.githubusercontent.com/che-incubator/devworkspace-api/proposal-25-variant-1-define-stacks/devfile-support/samples/nodejs-stack.devfile.yaml
  projects:
    - name: example
      git:
          branch: 'mybranch'
commands:
  - exec:
      id: sayHello
      label: Say Hello
      commandLine: echo "hello"
      component: nodejs