tfsdk: Prevent Attribute misconfiguration by consolidating Computed, …

…Optional, and Required fields into a single Configuration field

Reference: #31
Reference: #94

.changelog/pending.txt

@@ -0,0 +1,7 @@
+```release-note:breaking-change
+tfsdk: The `Attribute` type `Computed`, `Optional`, and `Required` fields have been replaced by `Configuration`.
+```
+
+```release-note:enhancement
+tfsdk: Prevent `Attribute` misconfiguration by consolidating `Computed`, `Optional`, and `Required` fields into a single `Configuration` field.
+```

tfsdk/attribute.go

@@ -30,6 +30,12 @@ type Attribute struct {
 	// If Attributes is set, Type cannot be.
 	Attributes NestedAttributes
 
+	// Configuration describes attribute value behaviors, such as whether the
+	// value must be configured by the practitioner. Must be defined.
+	//
+	// See AttributeConfiguration descriptions for additional information.
+	Configuration AttributeConfiguration
+
 	// Description is used in various tooling, like the language server, to
 	// give practitioners more information about what this attribute is,
 	// what it's for, and how it should be used. It should be written as
@@ -42,23 +48,6 @@ type Attribute struct {
 	// used. It should be formatted using Markdown.
 	MarkdownDescription string
 
-	// Required indicates whether the practitioner must enter a value for
-	// this attribute or not. Required and Optional cannot both be true,
-	// and Required and Computed cannot both be true.
-	Required bool
-
-	// Optional indicates whether the practitioner can choose not to enter
-	// a value for this attribute or not. Optional and Required cannot both
-	// be true.
-	Optional bool
-
-	// Computed indicates whether the provider may return its own value for
-	// this attribute or not. Required and Computed cannot both be true. If
-	// Required and Optional are both false, Computed must be true, and the
-	// attribute will be considered "read only" for the practitioner, with
-	// only the provider able to set its value.
-	Computed bool
-
 	// Sensitive indicates whether the value of this attribute should be
 	// considered sensitive data. Setting it to true will obscure the value
 	// in CLI output. Sensitive does not impact how values are stored, and
@@ -111,13 +100,7 @@ func (a Attribute) Equal(o Attribute) bool {
 	if a.MarkdownDescription != o.MarkdownDescription {
 		return false
 	}
-	if a.Required != o.Required {
-		return false
-	}
-	if a.Optional != o.Optional {
-		return false
-	}
-	if a.Computed != o.Computed {
+	if a.Configuration != o.Configuration {
 		return false
 	}
 	if a.Sensitive != o.Sensitive {
@@ -135,12 +118,23 @@ func (a Attribute) Equal(o Attribute) bool {
 func (a Attribute) tfprotov6SchemaAttribute(ctx context.Context, name string, path *tftypes.AttributePath) (*tfprotov6.SchemaAttribute, error) {
 	schemaAttribute := &tfprotov6.SchemaAttribute{
 		Name:      name,
-		Required:  a.Required,
-		Optional:  a.Optional,
-		Computed:  a.Computed,
 		Sensitive: a.Sensitive,
 	}
 
+	switch a.Configuration {
+	case AttributeConfigurationRequired:
+		schemaAttribute.Required = true
+	case AttributeConfigurationOptional:
+		schemaAttribute.Optional = true
+	case AttributeConfigurationOptionalComputed:
+		schemaAttribute.Optional = true
+		schemaAttribute.Computed = true
+	case AttributeConfigurationComputed:
+		schemaAttribute.Computed = true
+	default:
+		return nil, path.NewErrorf("must configure Configuration")
+	}
+
 	if a.DeprecationMessage != "" {
 		schemaAttribute.Deprecated = true
 	}
@@ -238,6 +232,17 @@ func (a Attribute) validate(ctx context.Context, req ValidateAttributeRequest, r
 		return
 	}
 
+	if a.Configuration == AttributeConfigurationUnknown {
+		resp.Diagnostics = append(resp.Diagnostics, &tfprotov6.Diagnostic{
+			Severity:  tfprotov6.DiagnosticSeverityError,
+			Summary:   "Invalid Attribute Definition",
+			Detail:    "Attribute missing Configuration definition. This is always a problem with the provider and should be reported to the provider developer.",
+			Attribute: req.AttributePath,
+		})
+
+		return
+	}
+
 	attributeConfig, diags := req.Config.GetAttribute(ctx, req.AttributePath)
 
 	resp.Diagnostics = append(resp.Diagnostics, diags...)

tfsdk/attribute_configuration.go

@@ -0,0 +1,51 @@
+package tfsdk
+
+// AttributeConfiguration describes Attribute value behaviors.
+type AttributeConfiguration int
+
+const (
+	// AttributeConfigurationUnknown signals an invalid Attribute definition.
+	//
+	// This is the default value of this type and is used to signal an
+	// Attribute missing a proper Configuration definition.
+	AttributeConfigurationUnknown AttributeConfiguration = 0
+
+	// AttributeConfigurationRequired denotes a value that requires practitioner configuration.
+	//
+	// If the practitioner configuration does not include a known value, an
+	// error is returned.
+	AttributeConfigurationRequired AttributeConfiguration = 1
+
+	// AttributeConfigurationOptional denotes a value that can be optionally set in a practitioner configuration.
+	//
+	// A plan difference for the value will be shown if plugin returns a value
+	// and there is no practitioner configuration.
+	AttributeConfigurationOptional AttributeConfiguration = 2
+
+	// AttributeConfigurationOptionalComputed denotes a value that can be set either by practitioner configuration or the plugin.
+	//
+	// No plan difference for the value will be shown if plugin returns a value
+	// and there is no practitioner configuration.
+	AttributeConfigurationOptionalComputed AttributeConfiguration = 3
+
+	// AttributeConfigurationComputed denotes a value that can only be set by the plugin.
+	//
+	// Effectively, this is a read-only Attribute.
+	AttributeConfigurationComputed AttributeConfiguration = 4
+)
+
+// String returns a string representation of the AttributeConfiguration.
+func (ac AttributeConfiguration) String() string {
+	switch ac {
+	case AttributeConfigurationRequired:
+		return "Required"
+	case AttributeConfigurationOptional:
+		return "Optional"
+	case AttributeConfigurationOptionalComputed:
+		return "OptionalComputed"
+	case AttributeConfigurationComputed:
+		return "Computed"
+	default:
+		return "Unknown"
+	}
+}