New Extra Check: Schema Elem should be *schema.Schema or *schema.Resource

[bflad]

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Description

While a helper/schema.Schema.Elem may contain a schema.ValueType Go type in some very limited cases (e.g. root TypeMap attributes), its support is limited, its not implemented in many providers, and otherwise can cause a panic in the Terraform Plugin SDK:

panic: invalid element type: schema.ValueType

For consistency and safety, a new extra check can recommend the more common &schema.Schema{Type: /* ... */} implementation.

New Checks

• XS###

Flagged Provider Code

&schema.Schema{
  Type: schema.TypeList,
  Elem: schema.TypeString,
}

Passing Provider Code

&schema.Schema{
  Type: schema.TypeList,
  Elem: &schema.Schema{
    Type: schema.TypeString,
  },
}

References

• https://github.com/hashicorp/terraform-plugin-sdk/blob/838e0bdc5dfb297e22aac0e7c263f718a067f553/helper/schema/serialize.go#L114-L125