tfsdk: Validate Attribute sets at least one of Required, Optional, or…

… Computed (#111)

Reference: #94

This can help schema consumers outside Terraform CLI ensure a valid schema is being defined.

.changelog/111.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+tfsdk: Validate `Attribute` defines at least one of `Required`, `Optional`, or `Computed`
+```

tfsdk/attribute.go

@@ -148,6 +148,10 @@ func (a Attribute) tfprotov6SchemaAttribute(ctx context.Context, name string, pa
 		Sensitive: a.Sensitive,
 	}
 
+	if !a.Required && !a.Optional && !a.Computed {
+		return nil, path.NewErrorf("must have Required, Optional, or Computed set")
+	}
+
 	if a.DeprecationMessage != "" {
 		schemaAttribute.Deprecated = true
 	}
@@ -245,6 +249,17 @@ func (a Attribute) validate(ctx context.Context, req ValidateAttributeRequest, r
 		return
 	}
 
+	if !a.Required && !a.Optional && !a.Computed {
+		resp.Diagnostics = append(resp.Diagnostics, &tfprotov6.Diagnostic{
+			Severity:  tfprotov6.DiagnosticSeverityError,
+			Summary:   "Invalid Attribute Definition",
+			Detail:    "Attribute missing Required, Optional, or Computed 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_test.go

@@ -641,6 +641,14 @@ func TestAttributeTfprotov6SchemaAttribute(t *testing.T) {
 			path:        tftypes.NewAttributePath(),
 			expectedErr: "must have Attributes or Type set",
 		},
+		"missing-required-optional-and-computed": {
+			name: "whoops",
+			attr: Attribute{
+				Type: types.StringType,
+			},
+			path:        tftypes.NewAttributePath(),
+			expectedErr: "must have Required, Optional, or Computed set",
+		},
 	}
 
 	for name, tc := range tests {
@@ -749,6 +757,37 @@ func TestAttributeValidate(t *testing.T) {
 				},
 			},
 		},
+		"missing-required-optional-and-computed": {
+			req: ValidateAttributeRequest{
+				AttributePath: tftypes.NewAttributePath().WithAttributeName("test"),
+				Config: Config{
+					Raw: tftypes.NewValue(tftypes.Object{
+						AttributeTypes: map[string]tftypes.Type{
+							"test": tftypes.String,
+						},
+					}, map[string]tftypes.Value{
+						"test": tftypes.NewValue(tftypes.String, "testvalue"),
+					}),
+					Schema: Schema{
+						Attributes: map[string]Attribute{
+							"test": {
+								Type: types.StringType,
+							},
+						},
+					},
+				},
+			},
+			resp: ValidateAttributeResponse{
+				Diagnostics: []*tfprotov6.Diagnostic{
+					{
+						Severity:  tfprotov6.DiagnosticSeverityError,
+						Summary:   "Invalid Attribute Definition",
+						Detail:    "Attribute missing Required, Optional, or Computed definition. This is always a problem with the provider and should be reported to the provider developer.",
+						Attribute: tftypes.NewAttributePath().WithAttributeName("test"),
+					},
+				},
+			},
+		},
 		"config-error": {
 			req: ValidateAttributeRequest{
 				AttributePath: tftypes.NewAttributePath().WithAttributeName("test"),