New function ValueFrom that takes a Go value and populates a compatible attr.Value, given a descriptive attr.Type

.changelog/350.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+tfsdk: New function `ValueFrom` that takes a Go value and populates a compatible `attr.Value`, given a descriptive `attr.Type`.
+```

tfsdk/value_as.go

@@ -9,9 +9,9 @@ import (
 	"github.com/hashicorp/terraform-plugin-framework/internal/reflect"
 )
 
-// ValueAs populates the Go value passed as `target` with
-// the contents of `val`, using the reflection rules
-// defined for `Get` and `GetAttribute`.
+// ValueAs takes the attr.Value `val` and populates the Go value `target` with its content.
+//
+// This is achieved using reflection rules provided by the internal/reflect package.
 func ValueAs(ctx context.Context, val attr.Value, target interface{}) diag.Diagnostics {
 	if reflect.IsGenericAttrValue(ctx, target) {
 		*(target.(*attr.Value)) = val

tfsdk/value_from.go

@@ -0,0 +1,23 @@
+package tfsdk
+
+import (
+	"context"
+
+	"github.com/hashicorp/terraform-plugin-framework/attr"
+	"github.com/hashicorp/terraform-plugin-framework/diag"
+	"github.com/hashicorp/terraform-plugin-framework/internal/reflect"
+	"github.com/hashicorp/terraform-plugin-go/tftypes"
+)
+
+// ValueFrom takes the Go value `val` and populates `target` with an attr.Value,
+// based on the type definition provided in `targetType`.
+//
+// This is achieved using reflection rules provided by the internal/reflect package.
+func ValueFrom(ctx context.Context, val interface{}, targetType attr.Type, target interface{}) diag.Diagnostics {
+	v, diags := reflect.FromValue(ctx, targetType, val, tftypes.NewAttributePath())
+	if diags.HasError() {
+		return diags
+	}
+
+	return ValueAs(ctx, v, target)
+}

tfsdk/value_from_test.go

@@ -0,0 +1,220 @@
+package tfsdk
+
+import (
+	"context"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/hashicorp/terraform-plugin-framework/attr"
+	"github.com/hashicorp/terraform-plugin-framework/diag"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+	"github.com/hashicorp/terraform-plugin-go/tftypes"
+)
+
+type person struct {
+	Name     types.String `tfsdk:"name"`
+	Age      types.Int64  `tfsdk:"age"`
+	OptedIn  types.Bool   `tfsdk:"opted_in"`
+	Address  types.List   `tfsdk:"address"`
+	FullName types.Map    `tfsdk:"full_name"`
+}
+
+func TestValueFrom(t *testing.T) {
+	t.Parallel()
+
+	personAttrTypes := map[string]attr.Type{
+		"name":     types.StringType,
+		"age":      types.Int64Type,
+		"opted_in": types.BoolType,
+		"address": types.ListType{
+			ElemType: types.StringType,
+		},
+		"full_name": types.MapType{
+			ElemType: types.StringType,
+		},
+	}
+
+	mrX := person{
+		Name:    types.String{Value: "x"},
+		Age:     types.Int64{Value: 30},
+		OptedIn: types.Bool{Value: true},
+		Address: types.List{
+			ElemType: types.StringType,
+			Elems: []attr.Value{
+				types.String{Value: "1"},
+				types.String{Value: "Beckford Close"},
+				types.String{Value: "Gotham"},
+			},
+		},
+		FullName: types.Map{
+			ElemType: types.StringType,
+			Elems: map[string]attr.Value{
+				"first":  types.String{Value: "x"},
+				"middle": types.String{Value: "b"},
+				"last":   types.String{Value: "c"},
+			},
+		},
+	}
+
+	mrsY := person{
+		Name:    types.String{Value: "y"},
+		Age:     types.Int64{Value: 23},
+		OptedIn: types.Bool{Value: false},
+		Address: types.List{
+			ElemType: types.StringType,
+			Elems: []attr.Value{
+				types.String{Value: "2"},
+				types.String{Value: "Windmill Close"},
+				types.String{Value: "Smallville"},
+			},
+		},
+		FullName: types.Map{
+			ElemType: types.StringType,
+			Elems: map[string]attr.Value{
+				"first":  types.String{Value: "y"},
+				"middle": types.String{Value: "e"},
+				"last":   types.String{Value: "f"},
+			},
+		},
+	}
+
+	expectedMrXObj := types.Object{
+		AttrTypes: personAttrTypes,
+		Attrs: map[string]attr.Value{
+			"name":     types.String{Value: "x", Unknown: false, Null: false},
+			"age":      types.Int64{Value: 30, Unknown: false, Null: false},
+			"opted_in": types.Bool{Value: true, Unknown: false, Null: false},
+			"address": types.List{
+				ElemType: types.StringType,
+				Elems: []attr.Value{
+					types.String{Value: "1"},
+					types.String{Value: "Beckford Close"},
+					types.String{Value: "Gotham"},
+				},
+			},
+			"full_name": types.Map{
+				ElemType: types.StringType,
+				Elems: map[string]attr.Value{
+					"first":  types.String{Value: "x"},
+					"middle": types.String{Value: "b"},
+					"last":   types.String{Value: "c"},
+				},
+			},
+		},
+	}
+
+	expectedMrsYObj := types.Object{
+		AttrTypes: personAttrTypes,
+		Attrs: map[string]attr.Value{
+			"name":     types.String{Value: "y", Unknown: false, Null: false},
+			"age":      types.Int64{Value: 23, Unknown: false, Null: false},
+			"opted_in": types.Bool{Value: false, Unknown: false, Null: false},
+			"address": types.List{
+				ElemType: types.StringType,
+				Elems: []attr.Value{
+					types.String{Value: "2"},
+					types.String{Value: "Windmill Close"},
+					types.String{Value: "Smallville"},
+				},
+			},
+			"full_name": types.Map{
+				ElemType: types.StringType,
+				Elems: map[string]attr.Value{
+					"first":  types.String{Value: "y"},
+					"middle": types.String{Value: "e"},
+					"last":   types.String{Value: "f"},
+				},
+			},
+		},
+	}
+
+	type testCase struct {
+		val           interface{}
+		target        attr.Value
+		expected      attr.Value
+		expectedDiags diag.Diagnostics
+	}
+
+	tests := map[string]testCase{
+		"primitive": {
+			val:      "hello",
+			target:   types.String{},
+			expected: types.String{Value: "hello", Unknown: false, Null: false},
+		},
+		"struct": {
+			val: mrX,
+			target: types.Object{
+				AttrTypes: personAttrTypes,
+			},
+			expected: expectedMrXObj,
+		},
+		"list": {
+			val: []person{mrX, mrsY},
+			target: types.List{
+				ElemType: types.ObjectType{
+					AttrTypes: personAttrTypes,
+				},
+			},
+			expected: types.List{
+				ElemType: types.ObjectType{
+					AttrTypes: personAttrTypes,
+				},
+				Elems: []attr.Value{expectedMrXObj, expectedMrsYObj},
+			},
+		},
+		"map": {
+			val: map[string]person{
+				"x": mrX,
+				"y": mrsY,
+			},
+			target: types.Map{
+				ElemType: types.ObjectType{
+					AttrTypes: personAttrTypes,
+				},
+			},
+			expected: types.Map{
+				ElemType: types.ObjectType{
+					AttrTypes: personAttrTypes,
+				},
+				Elems: map[string]attr.Value{
+					"x": expectedMrXObj,
+					"y": expectedMrsYObj,
+				},
+			},
+		},
+		"incompatible-type": {
+			val:    0,
+			target: types.String{},
+			expectedDiags: diag.Diagnostics{
+				diag.WithPath(
+					tftypes.NewAttributePath(),
+					diag.NewErrorDiagnostic(
+						"Value Conversion Error",
+						"An unexpected error was encountered trying to convert the Terraform value. This is always an error in the provider. Please report the following to the provider developer:\n\ncan't unmarshal tftypes.Number into *string, expected string",
+					),
+				),
+			},
+		},
+	}
+
+	for name, tc := range tests {
+		name, tc := name, tc
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			diags := ValueFrom(context.Background(), tc.val, tc.target.Type(context.Background()), &tc.target)
+
+			if diff := cmp.Diff(tc.expectedDiags, diags); diff != "" {
+				t.Fatalf("Unexpected diff in diagnostics (-wanted, +got): %s", diff)
+			}
+
+			if diags.HasError() {
+				return
+			}
+
+			if diff := cmp.Diff(tc.expected, tc.target); diff != "" {
+				t.Fatalf("Unexpected diff in results (-wanted, +got): %s", diff)
+			}
+		})
+	}
+}