listvalidator: Added UniqueValues validator (#88)

Reference: #67

.changelog/88.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+listvalidator: Added `UniqueValues` validator
+```

listvalidator/unique_values.go

@@ -0,0 +1,65 @@
+package listvalidator
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/hashicorp/terraform-plugin-framework/schema/validator"
+)
+
+var _ validator.List = uniqueValuesValidator{}
+
+// uniqueValuesValidator implements the validator.
+type uniqueValuesValidator struct{}
+
+// Description returns the plaintext description of the validator.
+func (v uniqueValuesValidator) Description(_ context.Context) string {
+	return "all values must be unique"
+}
+
+// MarkdownDescription returns the Markdown description of the validator.
+func (v uniqueValuesValidator) MarkdownDescription(ctx context.Context) string {
+	return v.Description(ctx)
+}
+
+// ValidateList implements the validation logic.
+func (v uniqueValuesValidator) ValidateList(_ context.Context, req validator.ListRequest, resp *validator.ListResponse) {
+	if req.ConfigValue.IsNull() || req.ConfigValue.IsUnknown() {
+		return
+	}
+
+	elements := req.ConfigValue.Elements()
+
+	for indexOuter, elementOuter := range elements {
+		// Only evaluate known values for duplicates.
+		if elementOuter.IsUnknown() {
+			continue
+		}
+
+		for indexInner := indexOuter + 1; indexInner < len(elements); indexInner++ {
+			elementInner := elements[indexInner]
+
+			if elementInner.IsUnknown() {
+				continue
+			}
+
+			if !elementInner.Equal(elementOuter) {
+				continue
+			}
+
+			resp.Diagnostics.AddAttributeError(
+				req.Path,
+				"Duplicate List Value",
+				fmt.Sprintf("This attribute contains duplicate values of: %s", elementInner),
+			)
+		}
+	}
+}
+
+// UniqueValues returns a validator which ensures that any configured list
+// only contains unique values. This is similar to using a set attribute type
+// which inherently validates unique values, but with list ordering semantics.
+// Null (unconfigured) and unknown (known after apply) values are skipped.
+func UniqueValues() validator.List {
+	return uniqueValuesValidator{}
+}

listvalidator/unique_values_example_test.go

@@ -0,0 +1,24 @@
+package listvalidator_test
+
+import (
+	"github.com/hashicorp/terraform-plugin-framework-validators/listvalidator"
+	"github.com/hashicorp/terraform-plugin-framework/datasource/schema"
+	"github.com/hashicorp/terraform-plugin-framework/schema/validator"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+)
+
+func ExampleUniqueValues() {
+	// Used within a Schema method of a DataSource, Provider, or Resource
+	_ = schema.Schema{
+		Attributes: map[string]schema.Attribute{
+			"example_attr": schema.ListAttribute{
+				ElementType: types.StringType,
+				Required:    true,
+				Validators: []validator.List{
+					// Validate this list must contain only unique values.
+					listvalidator.UniqueValues(),
+				},
+			},
+		},
+	}
+}

listvalidator/unique_values_test.go

@@ -0,0 +1,127 @@
+package listvalidator_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/hashicorp/terraform-plugin-framework-validators/listvalidator"
+	"github.com/hashicorp/terraform-plugin-framework/attr"
+	"github.com/hashicorp/terraform-plugin-framework/diag"
+	"github.com/hashicorp/terraform-plugin-framework/path"
+	"github.com/hashicorp/terraform-plugin-framework/schema/validator"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+)
+
+func TestUniqueValues(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		list                types.List
+		expectedDiagnostics diag.Diagnostics
+	}{
+		"null-list": {
+			list:                types.ListNull(types.StringType),
+			expectedDiagnostics: nil,
+		},
+		"unknown-list": {
+			list:                types.ListUnknown(types.StringType),
+			expectedDiagnostics: nil,
+		},
+		"null-value": {
+			list: types.ListValueMust(
+				types.StringType,
+				[]attr.Value{types.StringNull()},
+			),
+			expectedDiagnostics: nil,
+		},
+		"null-values-duplicate": {
+			list: types.ListValueMust(
+				types.StringType,
+				[]attr.Value{types.StringNull(), types.StringNull()},
+			),
+			expectedDiagnostics: diag.Diagnostics{
+				diag.NewAttributeErrorDiagnostic(
+					path.Root("test"),
+					"Duplicate List Value",
+					"This attribute contains duplicate values of: <null>",
+				),
+			},
+		},
+		"null-values-valid": {
+			list: types.ListValueMust(
+				types.StringType,
+				[]attr.Value{types.StringNull(), types.StringValue("test")},
+			),
+			expectedDiagnostics: nil,
+		},
+		"unknown-value": {
+			list: types.ListValueMust(
+				types.StringType,
+				[]attr.Value{types.StringUnknown()},
+			),
+			expectedDiagnostics: nil,
+		},
+		"unknown-values-duplicate": {
+			list: types.ListValueMust(
+				types.StringType,
+				[]attr.Value{types.StringUnknown(), types.StringUnknown()},
+			),
+			expectedDiagnostics: nil,
+		},
+		"unknown-values-valid": {
+			list: types.ListValueMust(
+				types.StringType,
+				[]attr.Value{types.StringUnknown(), types.StringValue("test")},
+			),
+			expectedDiagnostics: nil,
+		},
+		"known-value": {
+			list: types.ListValueMust(
+				types.StringType,
+				[]attr.Value{types.StringValue("test")},
+			),
+			expectedDiagnostics: nil,
+		},
+		"known-values-duplicate": {
+			list: types.ListValueMust(
+				types.StringType,
+				[]attr.Value{types.StringValue("test"), types.StringValue("test")},
+			),
+			expectedDiagnostics: diag.Diagnostics{
+				diag.NewAttributeErrorDiagnostic(
+					path.Root("test"),
+					"Duplicate List Value",
+					"This attribute contains duplicate values of: \"test\"",
+				),
+			},
+		},
+		"known-values-valid": {
+			list: types.ListValueMust(
+				types.StringType,
+				[]attr.Value{types.StringValue("test1"), types.StringValue("test2")},
+			),
+			expectedDiagnostics: nil,
+		},
+	}
+
+	for name, testCase := range testCases {
+		name, testCase := name, testCase
+
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			request := validator.ListRequest{
+				Path:           path.Root("test"),
+				PathExpression: path.MatchRoot("test"),
+				ConfigValue:    testCase.list,
+			}
+			response := validator.ListResponse{}
+			listvalidator.UniqueValues().ValidateList(context.Background(), request, &response)
+
+			if diff := cmp.Diff(response.Diagnostics, testCase.expectedDiagnostics); diff != "" {
+				t.Errorf("unexpected diagnostics difference: %s", diff)
+			}
+		})
+	}
+}