Processing files and folders in-place

[air3ijai]

Hello,

We found gomplate as a great alternative for sed and envsubst for Kubernetes manifest preprocessing.

We also found that we may process files and folders in-place:

# Same file
gomplate --file test.yaml --out test.yaml

# Same folder
gomplate --input-dir test-folder --output-dir test-folder

And we have some questions related to this

1. It is safe to preprocess files/folders in place?
2. Is there a switch to not use --out/--output-dir and just process same file/folder?

   gomplate --in-place --file test.yaml
   gomplate --in-place --input-dir test-folder
   

[hairyhenderson]

Hi @air3ijai, thanks for the questions - I've converted this to a Discussion since it does not appear to be a bug report or feature request.

1. It is safe to preprocess files/folders in place?

In general, it should be safe - gomplate reads the contents of each template into memory before rendering it, so the output file won't be written until after the input is read. Obviously, if you're processing a file in-place, it will be modified - that may not be considered "safe".

2. Is there a switch to not use --out/--output-dir and just process same file/folder?

No. It's pretty rare to do this as generally folks don't want templates to be modified, so I don't think it makes sense to add this as an implicit capability. But specifying the same file/dir for in/out works, so you can continue to do that.

Let me know if you have any other questions about this - hope this helped!

[air3ijai]

@hairyhenderson, thank you for moving that - will consider this for future questions.

We have a lot of stuff like

# envsubst
cat k8s/base/secrets.yaml | envsubst > k8s/base/secrets.yaml.tmp && mv k8s/base/secrets.yaml.tmp k8s/base/secrets.yaml

# sed
sed -i 's|{{NAMESPACE}}|${{ env.NAMESPACE }}|' k8s/overlays/${{ env.ENVIRONMENT_NAME }}/kustomization.yaml

and a simple alternative like this, looks very good

gomplate --file k8s/base/secrets.yaml --out k8s/base/secrets.yaml
gomplate --file k8s/overlays/${{ env.ENVIRONMENT_NAME }}/kustomization.yaml --out k8s/overlays/${{ env.ENVIRONMENT_NAME }}/kustomization.yaml

In our case we don't need to store template separately and manifests should be updated in-place, right before apply.

--in-place switch just can be more clean, without necessity to repeat same file/folder again

gomplate --in-place --file k8s/base/secrets.yaml
gomplate --in-place --file k8s/overlays/${{ env.ENVIRONMENT_NAME }}/kustomization.yaml

But for our case a solution like this, will replace a tens of commands

gomplate --input-dir k8s --output-dir k8s

Maybe someone else will ask same approach and you will consider a kind of --in-place for future releases.

Thank you for your work, Dave!