In CustomizedDiff the 2nd return value of d.GetChange on a nested block (TypeSet) doesn't contain inner nested block

[magodo]

SDK version

v1.6.0 & v1.13.0

Relevant provider source code

Schema definition:

"foo": {
    Type:     schema.TypeSet,
    Optional: true,
    Elem: &schema.Resource{
        Schema: map[string]*schema.Schema{
            "a": {
                Type:     schema.TypeString,
                Required: true,
            },

            "b": {
                Type:     schema.TypeList,
                Optional: true,
                MaxItems: 1,
                Elem: &schema.Resource{
                    Schema: map[string]*schema.Schema{
                        "x": {
                            Type:     schema.TypeBool,
                            Required: true,
                        },
                    },
                },
            },
        },
    },
}

Then define a CustomizeDiff, which in turns call d.GetChange("foo").

Expected Behavior

The returned "new" value of foo should contain the new state defined in terraform configuration.

Actual Behavior

The returned "new" value has foo.b with one element: nil.

Addtional Findings

I have debugged a bit on v1.6.0, and find the cause is that in readListField() it will modify the addrPadded to change the hash index of Set into a list index, which in turns will change affect the out address (as slice is passed by pointer in Go). In later step when d.GetChange wants to get the value from diff for an address, it can't find the value, hence setting it to nil.

The fix is simply copy the addrPadded to a temporary list before calling:

countResult, err := r.ReadField(addrPadded)

in file field_reader.go in readListField().

I suspect the same fix should be applied to the v1-maint branch.

[magodo]

@paddycarver Any update on this?

[arodriguezdlc]

Hello, this issue is blocking the resolution of hashicorp/terraform-provider-azurerm#7463. Is there any update about this? Thank you.

[Chandra2614]

Any update on this??