Added list of env variables for fn-plugins

[aodinokov]

KRM-functions should be able to get env variables.
After changes of runfn object fn based plugins don't
get them anymore.
Reflecting in build cmd args added in [1]
for fn run cmd.

[1]
#2988

[k8s-ci-robot]

Hi @aodinokov. Thanks for your PR.

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[aodinokov]

cc: @Shell32-Natsu

[Shell32-Natsu]

/ok-to-test
/lgtm

[Shell32-Natsu]

Can you add some tests in api/krusty/fnplugin_test.go? env should also be able to used in declarative files.

[aodinokov]

Can you add some tests in api/krusty/fnplugin_test.go? env should also be able to used in declarative files.

api/krusty/fnplugin_test.go runs tests with kpt-functions inside containers. that's a good idea to make something that passes env and expect the result based on the env variable value. the only concern, that I don't know any kpt-functions that need env variables. except 2 that I've written by myself :) That's why I'm not sure right now if it's possible to write a good test for that.

with std kpt-functions I may use envs values, but not sure how to check... will need to look inside to find a good one

[Shell32-Natsu]

OK, let's consider that later.

[monopole]

Thanks for the SOPs function in GoogleContainerTools/kpt-functions-catalog#101

by all means please contribute a simple test function in go that use env vars (e.g. accepts them and emits their values somewhere in the output).

https://github.com/GoogleContainerTools/kpt-functions-catalog/tree/master/functions/go

[aodinokov]

by all means please contribute a simple test function in go that use env vars (e.g. accepts them and emits their values somewhere in the output).

Was thinking about reusing already existing functions. helm_template looked promising, but it appeared that env functions is blocked (See warnings in the description).
I decided that it should be something meaningful and generic like envsubst, but at the same time - simple.

I ended up with this go-templater. Here is the ut that comply with our goal:

                        cfg: `
...
    template: |
      value: {{ env "TESTTEMPLATE" }}
`,
			expectedOut: `value: testtemplatevalue
`,

The implementation doesn't' look difficult to me, but of course it's not the simplest option. Is it simple enough?
see GoogleContainerTools/kpt-functions-catalog#103

[k8s-ci-robot]

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[aodinokov]

@monopole , @Shell32-Natsu

by all means please contribute a simple test function in go that use env vars (e.g. accepts them and emits their values somewhere in the output).

please find this test I've added:
64cbfbe#diff-97cedd4af5012b151e61e21710553cc6R479

it will be necessary to wait for GoogleContainerTools/kpt-functions-catalog#103 to be able to change image to gcr.io/kpt-functions/templater .
And with that PR it may also take some time: I needed a little hack to make this to be able to pass e2e:
GoogleContainerTools/kpt-functions-catalog@84f2c57#diff-60fe268f71ae7f8409aff40d0a3e51d8R70 . I expect that there will be some changes related to CI first to be able to test go-functions, + thorough review of my function... It may be a long story :)
may be I should split this PR on 2: with the original changes and with the added test?

[Shell32-Natsu]

Probably we should use one PR for both code and test. @monopole

[aodinokov]

Probably we should use one PR for both code and test.

np. actually I just realized that these changes I propose now are not so critical, since it's now possible to make the following the plugin config file and basically get the previous behaviour, but for the limited number of vars:

envs:
- envvarname1 #without setting the value
...

the changes you made for env vars there + setting a user to run container are awesome 👍

[monopole]

/lgtm