actions `pulumi-version-file` only works in install-only mode

What happened?

It seems that the pulumi-version-file input argument only works in install-only mode. I do not think this is expected behavior according to the documentation in the readme or in the PR: https://github.com/pulumi/actions/pull/1204

When in non-install-only mode

When running the following action config:

      - name: Preview <project-name> changes
        uses: pulumi/actions@v5
        env:
          PULUMI_CONFIG_PASSPHRASE: ${{ secrets.PULUMI_CONFIG_PASSPHRASE }}
        with:
          command: preview
          work-dir: ./projects/<project>
          comment-on-pr: true
          stack-name: prod
          pulumi-version-file: ./.pulumi.version
          cloud-url: ${{ steps.backend-url.outputs.result }}

I get this output:

> Run pulumi/actions@v5
  
Configured range: 
Matched version: v3.121.0
Install destination is /home/ubuntu/.pulumi
Successfully deleted pre-existing /home/ubuntu/.pulumi/bin
/usr/bin/tar xz --warning=no-unknown-keyword --overwrite -C /home/ubuntu/.pulumi -f /opt/actions-runner/_work/_temp/6800d063-e7de-41b2-86b5-d307745b54ce
Logging into s3://<i-removed-this>
pulumi preview on prod

Just to test, the content of the .pulumi.version file is:

3.120.0

When in install-only mode

      - name: Install Pulumi
        uses: pulumi/actions@v5
        with:
          pulumi-version-file: ./.pulumi.version
      - name: Preview <project-name> changes
        uses: pulumi/actions@v5
        env:
          PULUMI_CONFIG_PASSPHRASE: ${{ secrets.PULUMI_CONFIG_PASSPHRASE }}
        with:
          command: preview
          work-dir: ./projects/<project>
          comment-on-pr: true
          stack-name: prod
          pulumi-version-file: ./.pulumi.version
          cloud-url: ${{ steps.backend-url.outputs.result }}

Output:

# Install Pulumi
> Run pulumi/actions@v5
Configured range: 3.120.0
Matched version: v3.120.0
Install destination is /home/ubuntu/.pulumi
Successfully deleted pre-existing /home/ubuntu/.pulumi/bin
/usr/bin/tar xz --warning=no-unknown-keyword --overwrite -C /home/ubuntu/.pulumi -f /opt/actions-runner/_work/_temp/3cadc875-d728-485a-b0d5-18bd5df5536d
Pulumi has been successfully installed. Exiting.

# Preview <project-name> changes
> Run pulumi/actions@v5
Configured range: 
/opt/actions-runner/_work/_tool/pulumi/3.120.0/x64/pulumi version
v3.120.0
Pulumi version 3.120.0 has a known issue. Proceeding to download
Matched version: v3.121.0
Install destination is /home/ubuntu/.pulumi
Successfully deleted pre-existing /home/ubuntu/.pulumi/bin
/usr/bin/tar xz --warning=no-unknown-keyword --overwrite -C /home/ubuntu/.pulumi -f /opt/actions-runner/_work/_temp/1ea31476-34e3-48d1-874b-89a2915cc197
Logging into s3://<i-removed-this>
pulumi preview on prod

Example

The example comes from a GHES repo, but the following does not work:

When running the following action config:

      - name: Preview <project-name> changes
        uses: pulumi/actions@v5
        env:
          PULUMI_CONFIG_PASSPHRASE: ${{ secrets.PULUMI_CONFIG_PASSPHRASE }}
        with:
          command: preview
          work-dir: ./projects/<project>
          comment-on-pr: true
          stack-name: prod
          pulumi-version-file: ./.pulumi.version
          cloud-url: ${{ steps.backend-url.outputs.result }}

I get this output:

> Run pulumi/actions@v5
  
Configured range: 
Matched version: v3.121.0
Install destination is /home/ubuntu/.pulumi
Successfully deleted pre-existing /home/ubuntu/.pulumi/bin
/usr/bin/tar xz --warning=no-unknown-keyword --overwrite -C /home/ubuntu/.pulumi -f /opt/actions-runner/_work/_temp/6800d063-e7de-41b2-86b5-d307745b54ce
Logging into s3://<i-removed-this>
pulumi preview on prod

Just to test, the content of the .pulumi.version file is:

3.120.0

Output of `pulumi about`

CLI          
Version      3.121.0
Go Version   go1.22.4
Go Compiler  gc

Plugins
KIND      NAME    VERSION
resource  aws     6.42.0
language  nodejs  unknown
resource  tls     5.0.3

Host     
OS       ubuntu
Version  22.04
Arch     x86_64

This project is written in nodejs: executable='/home/<user>/.nvm/versions/node/v18.20.3/bin/node' version='v18.20.3'

Backend        
Name           <computer-name>
URL            s3://<s3-bucket>
User           <user>
Organizations  
Token type     personal

Additional context

In the config.ts file pulumi-version-file input is only read in makeInstallationConfig:

https://github.com/pulumi/actions/blob/760956aff50b515c197ee22d30aa8d756f7b86a2/src/config.ts#L27

installationConfig is only valid when command is undefined, so in main.ts the if statement checking downloadConfig.success is skipped when not in install-only mode:

https://github.com/pulumi/actions/blob/760956aff50b515c197ee22d30aa8d756f7b86a2/src/main.ts#L23-L28

So, when not in install-only mode, then full config does not use pulumi-version-file. Also, I suspect getInput('pulumi-version') returns an empty string causing pulumiVersion to be an empty string, rather than ^3 (I'm thinking this because of the outputted line Configured range: which should end with the value from pulumiVersion).

https://github.com/pulumi/actions/blob/760956aff50b515c197ee22d30aa8d756f7b86a2/src/main.ts#L32-L34

https://github.com/pulumi/actions/blob/760956aff50b515c197ee22d30aa8d756f7b86a2/src/main.ts#L43-L44

Contributing

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