tfsdk: GetAttribute panic for nested object in missing/null attribute

[bluekeyes]

Module version

github.com/hashicorp/terraform-plugin-framework v0.4.3-0.20211006203044-2d173e3470f6

Relevant provider source code

I discovered this issue in a resource with this (partial) schema:

return tfsdk.Schema{
    Attributes: map[string]tfsdk.Attribute{
        "patches": {
            Optional: true,
            Attributes: tfsdk.ListNestedAttributes(map[string]tfsdk.Attribute{
                "content": {
                    Type:     types.StringType,
                    Required: true,
                },
                "target": {
                    Optional: true,
                    Attributes: tfsdk.SingleNestedAttributes(map[string]tfsdk.Attribute{
                        "name": {
                            Type:     types.StringType,
                            Optional: true,
                        },
                        // more optional attributes...
                    }),
                },
            }, tfsdk.ListNestedAttributesOptions{}),
        },
    },
}

I can include additional provider code if needed, but the panic stack is entirely in the framework so hopefully the unit test reproduction included below is sufficient.

Terraform Configuration Files

resource "myprovider_resource" "test" {
  patches = [
    {
      content = file("/path/to/file.patch"),
      target = {
        name = "test"
      }
    }
  ]
}

The resource exists in state and was initially created without the patches property. Adding patches and planning triggers the crash.

Expected Behavior

Terraform executes a plan without crashing, showing patches changing from empty/unset to the content above.

Actual Behavior

The provider panics:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x11e2385]

goroutine 25 [running]:
github.com/hashicorp/terraform-plugin-framework/types.ObjectType.ValueFromTerraform(0xc000174c60, 0x18fe2b0, 0xc00079e140, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-framework/types/object.go:55 +0x65
github.com/hashicorp/terraform-plugin-framework/tfsdk.State.GetAttribute(0x1903f28, 0xc00064e6f0, 0x1737b00, 0xc00017bd10, 0xc000156330, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-framework/tfsdk/state.go:74 +0x624
github.com/hashicorp/terraform-plugin-framework/tfsdk.Attribute.modifyPlan(0x0, 0x0, 0x1904d78, 0xc000156420, 0x0, 0x0, 0x0, 0x0, 0x100, 0x0, ...)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-framework/tfsdk/attribute.go:458 +0x19a
github.com/hashicorp/terraform-plugin-framework/tfsdk.modifyAttributesPlans(0x18fe2b0, 0xc00079e140, 0xc0001563f0, 0xc0004ad368, 0x1903f28, 0xc000121470, 0x1737b00, 0xc000156d50, 0xc000156330, 0x0, ...)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-framework/tfsdk/schema.go:245 +0x528
github.com/hashicorp/terraform-plugin-framework/tfsdk.modifyAttributesPlans(0x18fe2b0, 0xc00079e140, 0xc000156330, 0xc0001450c0, 0x1903f28, 0xc000121470, 0x1737b00, 0xc000156d50, 0xc000156330, 0x0, ...)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-framework/tfsdk/schema.go:275 +0xae8
github.com/hashicorp/terraform-plugin-framework/tfsdk.Schema.modifyAttributePlans(...)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-framework/tfsdk/schema.go:222
github.com/hashicorp/terraform-plugin-framework/tfsdk.(*server).planResourceChange(0xc00046a5a0, 0x18fe2b0, 0xc00079e140, 0xc0005d2460, 0xc000145a90)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-framework/tfsdk/serve.go:810 +0x1848
github.com/hashicorp/terraform-plugin-framework/tfsdk.(*server).PlanResourceChange(0xc00046a5a0, 0x18fe2b0, 0xc00079e100, 0xc0005d2460, 0xc00079e100, 0x17e40a0, 0xc000156000)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-framework/tfsdk/serve.go:635 +0xc8
github.com/hashicorp/terraform-plugin-go/tfprotov6/tf6server.(*server).PlanResourceChange(0xc00023ea00, 0x18fe358, 0xc00079e100, 0xc00045e000, 0xc00023ea00, 0xc000156030, 0xc000089ba0)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-go/tfprotov6/tf6server/server.go:314 +0xb5
github.com/hashicorp/terraform-plugin-go/tfprotov6/internal/tfplugin6._Provider_PlanResourceChange_Handler(0x17e40a0, 0xc00023ea00, 0x18fe358, 0xc000156030, 0xc000280300, 0x0, 0x18fe358, 0xc000156030, 0xc000168000, 0x42a6)
	/Users/bkeyes/code/my-provider/vendor/github.com/hashicorp/terraform-plugin-go/tfprotov6/internal/tfplugin6/tfplugin6_grpc.pb.go:363 +0x214
google.golang.org/grpc.(*Server).processUnaryRPC(0xc0003a3180, 0x19052b8, 0xc000603200, 0xc0000c8200, 0xc00046a690, 0x1cf0de8, 0x0, 0x0, 0x0)
	/Users/bkeyes/code/my-provider/vendor/google.golang.org/grpc/server.go:1194 +0x52b
google.golang.org/grpc.(*Server).handleStream(0xc0003a3180, 0x19052b8, 0xc000603200, 0xc0000c8200, 0x0)
	/Users/bkeyes/code/my-provider/vendor/google.golang.org/grpc/server.go:1517 +0xd05
google.golang.org/grpc.(*Server).serveStreams.func1.2(0xc000038290, 0xc0003a3180, 0x19052b8, 0xc000603200, 0xc0000c8200)
	/Users/bkeyes/code/my-provider/vendor/google.golang.org/grpc/server.go:859 +0xab
created by google.golang.org/grpc.(*Server).serveStreams.func1
	/Users/bkeyes/code/my-provider/vendor/google.golang.org/grpc/server.go:857 +0x1fd

Steps to Reproduce

Add this test to StateGetAttributeTest in tfsdk/state_test.go and run the tests:

"WithAttributeName-ListNestedAttributes-null-WithElementKeyInt-WithAttributeName-object": {
    state: State{
        Raw: tftypes.NewValue(tftypes.Object{
            AttributeTypes: map[string]tftypes.Type{
                "test": tftypes.List{
                    ElementType: tftypes.Object{
                        AttributeTypes: map[string]tftypes.Type{
                            "sub_test": tftypes.Object{
                                AttributeTypes: map[string]tftypes.Type{
                                    "value": tftypes.String,
                                },
                            },
                        },
                    },
                },
                "other": tftypes.Bool,
            },
        }, map[string]tftypes.Value{
            "test": tftypes.NewValue(tftypes.List{
                ElementType: tftypes.Object{
                    AttributeTypes: map[string]tftypes.Type{
                        "sub_test": tftypes.Object{
                            AttributeTypes: map[string]tftypes.Type{
                                "value": tftypes.String,
                            },
                        },
                    },
                },
            }, nil),
            "other": tftypes.NewValue(tftypes.Bool, nil),
        }),
        Schema: Schema{
            Attributes: map[string]Attribute{
                "test": {
                    Attributes: ListNestedAttributes(map[string]Attribute{
                        "sub_test": {
                            Attributes: SingleNestedAttributes(map[string]Attribute{
                                "value": {
                                    Type:     types.StringType,
                                    Optional: true,
                                },
                            }),
                            Optional: true,
                        },
                    }, ListNestedAttributesOptions{}),
                    Optional: true,
                },
                "other": {
                    Type:     types.BoolType,
                    Optional: true,
                },
            },
        },
    },
    path: tftypes.NewAttributePath().WithAttributeName("test").WithElementKeyInt(0).WithAttributeName("sub_test"),
    expected: types.Object{
        Null:      true,
        AttrTypes: map[string]attr.Type{"value": types.StringType},
    },
},

References

• I originally encountered the problem from "step cannot be applied to this value" failure after before update if nested attribute was previously null #150 and updated to the latest development commit, which led to this panic
• The fix from tfsdk: Return null value when missing from Config, Plan, and State GetAttribute() method #185 creates a situation where a tftypes.Value with a nil type is passed to types.Object#ValueFromTerraform.

Other Thoughts

In types.Object#ValueFromTerraform, I can fix the failing test by either:

1. Adding a check that in.Type() is not nil before calling Equal
2. Moving the IsKnown and IsNull checks before the type check

I can submit a PR with the test and a fix, but I'm not sure which option is best, or if there are any other similar cases that need fixes.

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