Allow the HCL input when prompted

We already accept HCL encoded input for -vars, and this expands that to
accept HCL when prompted for a value on the command line as well.

terraform/context.go

@@ -317,16 +317,18 @@ func (c *Context) Input(mode InputMode) error {
 				}
 			}
 
+			var valueType config.VariableType
+
 			v := m[n]
-			switch v.Type() {
+			switch valueType = v.Type(); valueType {
 			case config.VariableTypeUnknown:
 				continue
 			case config.VariableTypeMap:
-				continue
+				// OK
 			case config.VariableTypeList:
-				continue
+				// OK
 			case config.VariableTypeString:
-				// Good!
+				// OK
 			default:
 				panic(fmt.Sprintf("Unknown variable type: %#v", v.Type()))
 			}
@@ -340,6 +342,12 @@ func (c *Context) Input(mode InputMode) error {
 				}
 			}
 
+			// this should only happen during tests
+			if c.uiInput == nil {
+				log.Println("[WARN] Content.uiInput is nil")
+				continue
+			}
+
 			// Ask the user for a value for this variable
 			var value string
 			retry := 0
@@ -355,27 +363,33 @@ func (c *Context) Input(mode InputMode) error {
 						"Error asking for %s: %s", n, err)
 				}
 
-				if value == "" && v.Required() {
-					// Redo if it is required, but abort if we keep getting
-					// blank entries
-					if retry > 2 {
-						return fmt.Errorf("missing required value for %q", n)
-					}
-					retry++
-					continue
-				}
-
 				if value == "" {
-					// No value, just exit the loop. With no value, we just
-					// use whatever is currently set in variables.
-					break
+					if v.Required() {
+						// Redo if it is required, but abort if we keep getting
+						// blank entries
+						if retry > 2 {
+							return fmt.Errorf("missing required value for %q", n)
+						}
+						retry++
+						continue
+					}
 				}
 
 				break
 			}
 
-			if value != "" {
-				c.variables[n] = value
+			// no value provided, so don't set the variable at all
+			if value == "" {
+				continue
+			}
+
+			decoded, err := parseVariableAsHCL(n, value, valueType)
+			if err != nil {
+				return err
+			}
+
+			if decoded != nil {
+				c.variables[n] = decoded
 			}
 		}
 	}
@@ -656,9 +670,20 @@ func (c *Context) walk(
 // the name of the variable. In order to get around the restriction of HCL requiring a
 // top level object, we prepend a sentinel key, decode the user-specified value as its
 // value and pull the value back out of the resulting map.
-func parseVariableAsHCL(name string, input interface{}, targetType config.VariableType) (interface{}, error) {
+func parseVariableAsHCL(name string, input string, targetType config.VariableType) (interface{}, error) {
+	// expecting a string so don't decode anything, just strip quotes
 	if targetType == config.VariableTypeString {
-		return input, nil
+		return strings.Trim(input, `"`), nil
+	}
+
+	// return empty types
+	if strings.TrimSpace(input) == "" {
+		switch targetType {
+		case config.VariableTypeList:
+			return []interface{}{}, nil
+		case config.VariableTypeMap:
+			return make(map[string]interface{}), nil
+		}
 	}
 
 	const sentinelValue = "SENTINEL_TERRAFORM_VAR_OVERRIDE_KEY"

terraform/context_input_test.go

@@ -617,3 +617,44 @@ func TestContext2Input_interpolateVar(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 }
+
+func TestContext2Input_hcl(t *testing.T) {
+	input := new(MockUIInput)
+	m := testModule(t, "input-hcl")
+	p := testProvider("hcl")
+	p.ApplyFn = testApplyFn
+	p.DiffFn = testDiffFn
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"hcl": testProviderFuncFixed(p),
+		},
+		Variables: map[string]interface{}{},
+		UIInput:   input,
+	})
+
+	input.InputReturnMap = map[string]string{
+		"var.listed": `["a", "b"]`,
+		"var.mapped": `{x = "y", w = "z"}`,
+	}
+
+	if err := ctx.Input(InputModeVar | InputModeVarUnset); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if _, err := ctx.Plan(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	state, err := ctx.Apply()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	actualStr := strings.TrimSpace(state.String())
+	expectedStr := strings.TrimSpace(testTerraformInputHCL)
+	if actualStr != expectedStr {
+		t.Logf("expected: \n%s", expectedStr)
+		t.Fatalf("bad: \n%s", actualStr)
+	}
+}

terraform/context_test.go

@@ -6,6 +6,8 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/hashicorp/terraform/flatmap"
 )
 
 func TestNewContextState(t *testing.T) {
@@ -172,7 +174,16 @@ func testDiffFn(
 		if reflect.DeepEqual(v, []interface{}{}) {
 			attrDiff.New = ""
 		} else {
-			attrDiff.New = v.(string)
+			if s, ok := v.(string); ok {
+				attrDiff.New = s
+			} else {
+				// the value is something other than a string
+				// flatmap it, adding the diff for each value.
+				for k, attrDiff := range testFlatAttrDiffs(k, v) {
+					diff.Attributes[k] = attrDiff
+				}
+				continue
+			}
 		}
 
 		if k == "require_new" {
@@ -219,6 +230,22 @@ func testDiffFn(
 	return diff, nil
 }
 
+// generate ResourceAttrDiffs for nested data structures in tests
+func testFlatAttrDiffs(k string, i interface{}) map[string]*ResourceAttrDiff {
+	flat := flatmap.Flatten(map[string]interface{}{k: i})
+	diffs := make(map[string]*ResourceAttrDiff)
+
+	for k, v := range flat {
+		attrDiff := &ResourceAttrDiff{
+			Old: "",
+			New: v,
+		}
+		diffs[k] = attrDiff
+	}
+
+	return diffs
+}
+
 func testProvider(prefix string) *MockResourceProvider {
 	p := new(MockResourceProvider)
 	p.RefreshFn = func(info *InstanceInfo, s *InstanceState) (*InstanceState, error) {

terraform/terraform_test.go

@@ -1413,3 +1413,14 @@ module.mod2:
 STATE:
 
 <no state>`
+
+const testTerraformInputHCL = `
+hcl_instance.hcltest:
+  ID = foo
+  bar.w = z
+  bar.x = y
+  foo.# = 2
+  foo.0 = a
+  foo.1 = b
+  type = hcl_instance
+`

terraform/test-fixtures/input-hcl/main.tf

@@ -0,0 +1,12 @@
+variable "mapped" {
+    type = "map"
+}
+
+variable "listed" {
+    type = "list"
+}
+
+resource "hcl_instance" "hcltest" {
+    foo = "${var.listed}"
+    bar = "${var.mapped}"
+}