User-supplied, empty values in the provider configuration should not be ignored and unused

[SarahFrench]

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Terraform Version

N/A
This is related to a defect identified after introduction of v4.60.2
We have fixed the provider to have parity with the old behaviour, but in 5.0.0 we should remove the behaviour seen in <=4.59.0

Affected Resource(s)

N/A - is related to provider config

Terraform Configuration Files

Provider is configured by:

• Running gcloud auth application-default login
• Not having any ENVs for configuring the provider present

provider "google" {
  credentials = ""
}

Debug Output

N/A

Expected Behavior

When a user sets a value in their configuration it should override any environment variables. If a user sets credentials = "", or project="" (for example) then the provider should attempt to use that value.

Actual Behavior

In the old SDK version of the provider <=4.59.0 empty strings would be ignored and ENVs would be used instead.
After muxing was introduced to the provider the ignoring stopped, and we then changed to code to ensure parity with the un-muxed code.
Currently empty strings are ignored in provider configurations.

Steps to Reproduce

1. Local environment setup
   a. Running gcloud auth application-default login
   b. Unset any ENVs for configuring the provider
2. Make a TF config where the provider config block includes an empty string as an argument, e.g. credentials = ""
3. terraform apply <- error occurs here

Important Factoids

The reason empty strings were ignored in the past is because the SDK made it hard to distinguish between Go's zero values and user-supplied values. After values were taken out of the ResourceData struct for the provider you lose any information about whether the value was set or not. Structs made using values from the provider config, i.e. the Config struct, have no way to distinguish between zero values and user values that match.

References

• Original issue where this was reported: Provider configuration values supplied as empty strings/zero-values are no longer treated like null values (muxed provider, v4.60.2+) #14255

[SarahFrench]

This change could include addition of validation functions like : https://developer.hashicorp.com/terraform/plugin/framework/providers/validate-configuration#validateconfig-method

[rileykarson]

Note: We may need to watch out for an intersection with GoogleCloudPlatform/magic-modules#8569, we probably just want to test a couple of cases

[SarahFrench]

Issue is still open due because GoogleCloudPlatform/magic-modules#9050 is needed to add user-facing validation on provider config values

[c2thorn]

Closed with GoogleCloudPlatform/magic-modules#9050

[github-actions]

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