Setting default values on non-primitive types does not fail schema validation.

What happened?

This was raised internally: https://pulumi.slack.com/archives/C045N7FDGHW/p1719386921192569.

Example

To summarize:

A bridged provider maintainer set a default value (via env) for a provider configuration value.

                "defaultInfo": {
                    "environment": [
                        "GRAFANA_CLOUD_ACCESS_POLICY_TOKEN"
                    ]
                },

At minimum, this generates invalid C# code:

https://github.com/pulumiverse/pulumi-grafana/pull/175/files#diff-95b29f66b24fa6371a2f80b462b9bf6222b7ae1a30b703b88d47d207b2c49e2aR119

The code doesn't type check:

Error: /home/runner/work/pulumi-grafana/pulumi-grafana/sdk/dotnet/Config/Config.cs(119,127): error CS0019: Operator '??' cannot be applied to operands of type 'ImmutableArray<string>' and 'string' [/home/runner/work/pulumi-grafana/pulumi-grafana/sdk/dotnet/Pulumiverse.Grafana.csproj]

Output of `pulumi about`

NA. Codegen was on v3.118.0.

Additional context

Waiting until we check if SDKs compile is confusing to users and might not catch the bug until runtime for a python based provider. Pulumi should fail fast when invalid default values are supplied and give the user an actionable error message.

Contributing

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pulumi / pulumi