Convert to number error when storing a value in float64 during execution of provider-defined function

[bendbennett]

Module version

v1.5.0

Relevant provider source code

var _ function.Function = Float64Function{}

func NewFloat64Function() function.Function {
	return &Float64Function{}
}

type Float64Function struct{}

func (f Float64Function) Metadata(ctx context.Context, req function.MetadataRequest, resp *function.MetadataResponse) {
	resp.Name = "float64"
}

func (f Float64Function) Definition(ctx context.Context, req function.DefinitionRequest, resp *function.DefinitionResponse) {
	resp.Definition = function.Definition{
		Parameters: []function.Parameter{
			function.Float64Parameter{},
		},
		Return: function.Float64Return{},
	}
}

func (f Float64Function) Run(ctx context.Context, req function.RunRequest, resp *function.RunResponse) {
	var arg float64

	resp.Diagnostics.Append(req.Arguments.Get(ctx, &arg)...)

	resp.Diagnostics.Append(resp.Result.Set(ctx, arg)...)
}

func TestFloat64Function_known(t *testing.T) {
	resource.UnitTest(t, resource.TestCase{
		TerraformVersionChecks: []tfversion.TerraformVersionCheck{
			tfversion.SkipBelow(tfversion.Version1_7_0),
		},
		ProtoV6ProviderFactories: map[string]func() (tfprotov6.ProviderServer, error){
			"framework": providerserver.NewProtocol6WithError(New()),
		},
		Steps: []resource.TestStep{
			{
				Config: `
				output "test" {
					value = provider::framework::float64(1.23)
				}`,
				ConfigStateChecks: []statecheck.StateCheck{
					statecheck.ExpectKnownOutputValue("test", knownvalue.Float64Exact(1.23)),
				},
			},
		},
	})
}

Terraform Configuration Files

Following is the configuration used during execution of the test.

output "test" {
	value = provider::framework::float64(1.23)
}

Debug Output

https://gist.github.com/bendbennett/ea6aadc53b2e53e66eda630f6b638e64

Expected Behavior

Test should run sucessfully.

Actual Behavior

Following error is generated:

=== RUN   TestFloat64Function_known
    float64_function_test.go:20: Step 1/1 error: Error running pre-apply plan: exit status 1
        
        Error: Error in function call
        
          on terraform_plugin_test.tf line 13, in output "test":
          13: 					value = provider::framework::float64(1.23)
            ├────────────────
            │ while calling provider::framework::float64(param)
        
        Call to function "provider::framework::float64" failed: Value Conversion
        Error: An unexpected error was encountered trying to convert to number. This
        is always an error in the provider. Please report the following to the
        provider developer:
        
        cannot store 1.23 in float64.
--- FAIL: TestFloat64Function_known (0.15s)

Steps to Reproduce

1. Requires a build of the Terraform binary from main (until such time as v1.8.0 is released).
2. Test described is included as part of Adding Provider-Defined Function Testing, a specific example being TestFloat64Function_known

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