Infracost estimate: monthly cost will increase by $0.00 - When base branch is empty about actions HOT 5 CLOSED

Thanks @kaykhan, yeah this seems like something that could be accounted for in the Infracost CLI itself. We don't have a solution for that just now, but it's something we should probably consider.

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@kaykhan thanks for reporting. In the pipeline what are you passing in as inputs.TF_ROOT?

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@kaykhan thanks for reporting. In the pipeline what are you passing in as inputs.TF_ROOT?

To be clear terraform-ci.yaml is a reusable workflow (updated original post to show that). This reusable workflow is triggered via the below workflow.

TF_ROOT is applications/prod/msk

msk-prod-tf-ci.yaml

name: msk-prod-tf-ci

on:
  pull_request:
    paths: ['applications/prod/msk/**']
    
concurrency:
  group: terraform

jobs:
  ci:
    uses: ./.github/workflows/terraform-ci.yaml
    with: 
      TF_ROOT: applications/prod/msk
      TF_APP_NAME: msk-prod
    secrets: inherit

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Thanks @kaykhan. My initial thoughts are since you are passing in applications/prod/msk as the path to Infracost, then when it runs against the base branch it is actually erroring, instead of producing an empty output since that dir doesn't exist in that branch. Since the base branch is erroring for that project then the diff command will fail as well for that project.

One way to resolve this would be to use an Infracost config file to dynamically find the project directories that exist on each given branch.

Something like this infracost.yml.tmpl might work for your case:

version: 0.1
projects:
{{- range $project := matchPaths "applications/:env/:name" }}
    - path: {{ $project._path }}
      name: {{ $project.env }}/{{ $project.name }}
{{- end }}

And then updating your pipeline to generate the config.

For the base run:

infracost generate config --repo-path=. \
    --template-path=infracost.yml.tmpl \
    --out-file=infracost.yml
infracost breakdown --config-file=infracost.yml \
    --format=json \
    --out-file=/tmp/infracost-base.json

For the diff run:

infracost generate config --repo-path=. \
    --template-path=infracost.yml.tmpl \
    --out-file=infracost.yml
infracost diff --config-file=infracost.yml \
    --format=json \
    --compare-to=/tmp/infracost-base.json \
    --out-file=/tmp/infracost.json

Another option that might be simpler to test initially is just to ensure the directory exists when you run the base branch, i.e.:

mkdir -p ${{ inputs.TF_ROOT }}
infracost breakdown --path=${{ inputs.TF_ROOT }} \
    --format=json \
    --out-file=/tmp/infracost-base.json

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Alright i'll have to try the infracost config file another time.

Another option that might be simpler to test initially is just to ensure the directory exists when you run the base branch, i.e.:

Tested this just now and of course there is an additional error. No valid Terraform files found at path applications/prod/msk (main branch is emtpy)

What i am thinking of doing is checking for the presence of the folder inputs.TF_ROOT in an initial step.

  - name: Check baseline exists
    run: |

Based on the result of that step i can either continue to run the baseline + diff or just run the breakdown directly.

Maybe i was hoping for an extra flag that could be added to infracost diff (ignore any errors that are in infracost-base.json and run the breakdown) to do this but i dont know if this would introduce some unforeseen conflicts.

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