makeTerraformInputs converts empty strings wrong

[VenelinMartinov]

What happened?

discovered in #1913

We convert empty strings wrong.

Example

func TestInputsEmptyString(t *testing.T) {
	t.Skip("Empty strings are misrepresented")
	runCreateInputCheck(t, inputTestCase{
		Resource: &schema.Resource{
			Schema: map[string]*schema.Schema{
				"f0": {
					Type:     schema.TypeString,
					Required: true,
				},
			},
		},
		Config: tftypes.NewValue(
			tftypes.Object{
				AttributeTypes: map[string]tftypes.Type{
					"f0": tftypes.String,
				},
			},
			map[string]tftypes.Value{
				"f0": tftypes.NewValue(tftypes.String, ""),
			}),
	})
}

Output of pulumi about

.

Additional context

No response

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[iwahbe]

@VenelinMartinov How do we convert empty strings vs what they should be? Can you post a diff (what we do vs what tf does)?

[t0yv0]

I'd be curious to have some more detail here as well. I think I have an intuition about why set-nested blocks should convert as empty sets instead of null, but strings?

[VenelinMartinov]

This is what I got in TestInputsEmptyString:

Resource: &schema.Resource{
	Schema: map[string]*schema.Schema{
		"f0": {
			Type:     schema.TypeString,
			Required: true,
		},
	},
},
Config: tftypes.NewValue(
	tftypes.Object{
		AttributeTypes: map[string]tftypes.Type{
			"f0": tftypes.String,
		},
	},
	map[string]tftypes.Value{
		"f0": tftypes.NewValue(tftypes.String, ""),
	},
),

TF value cty.ObjectVal(map[string]cty.Value{"f0":cty.StringVal(""), "id":cty.UnknownVal(cty.String)})
PU value cty.ObjectVal(map[string]cty.Value{"f0":cty.NullVal(cty.String), "id":cty.NullVal(cty.String)})

We seem to use NullVal(cty.String) while TF returns cty.StringVal("") in RawPlan

[t0yv0]

That's under Required: true? Does it hold under Optional: true?

[t0yv0]

Wait hold on a second, Pulumi substitutes null for ""? That's very surprising. Might be worth double checking that we print a correct Pulumi program and it's not some kind of test harness issue.

[VenelinMartinov]

backend:
    url: file://./data
name: project
resources:
    example:
        properties:
            f0: ""
        type: crossprovider:index:TestRes
runtime: yaml

resource "crossprovider_testres" "example" {
  f0 = ""
}

Same thing for Optional: true.

I've also checked that #1971 fixes this so it must be UpgradeState at fault here.

[t0yv0]

I'm a little mindblown and very glad we got a fix for this.