Fix HCL2 code generation for slices within another slice (#8669)

builder/amazon/chroot/builder.hcl2spec.go

@@ -120,7 +120,7 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"token":                         &hcldec.AttrSpec{Name: "token", Type: cty.String, Required: false},
 		"vault_aws_engine":              &hcldec.BlockSpec{TypeName: "vault_aws_engine", Nested: hcldec.ObjectSpec((*common.FlatVaultAWSEngineOptions)(nil).HCL2Spec())},
 		"ami_block_device_mappings":     &hcldec.BlockListSpec{TypeName: "ami_block_device_mappings", Nested: hcldec.ObjectSpec((*common.FlatBlockDevice)(nil).HCL2Spec())},
-		"chroot_mounts":                 &hcldec.BlockListSpec{TypeName: "chroot_mounts", Nested: &hcldec.AttrSpec{Name: "chroot_mounts", Type: cty.List(cty.String), Required: false}},
+		"chroot_mounts":                 &hcldec.AttrSpec{Name: "chroot_mounts", Type: cty.List(cty.List(cty.String)), Required: false},
 		"command_wrapper":               &hcldec.AttrSpec{Name: "command_wrapper", Type: cty.String, Required: false},
 		"copy_files":                    &hcldec.AttrSpec{Name: "copy_files", Type: cty.List(cty.String), Required: false},
 		"device_path":                   &hcldec.AttrSpec{Name: "device_path", Type: cty.String, Required: false},

builder/azure/chroot/builder.hcl2spec.go

@@ -78,7 +78,7 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"mount_partition":              &hcldec.AttrSpec{Name: "mount_partition", Type: cty.String, Required: false},
 		"mount_path":                   &hcldec.AttrSpec{Name: "mount_path", Type: cty.String, Required: false},
 		"post_mount_commands":          &hcldec.AttrSpec{Name: "post_mount_commands", Type: cty.List(cty.String), Required: false},
-		"chroot_mounts":                &hcldec.BlockListSpec{TypeName: "chroot_mounts", Nested: &hcldec.AttrSpec{Name: "chroot_mounts", Type: cty.List(cty.String), Required: false}},
+		"chroot_mounts":                &hcldec.AttrSpec{Name: "chroot_mounts", Type: cty.List(cty.List(cty.String)), Required: false},
 		"copy_files":                   &hcldec.AttrSpec{Name: "copy_files", Type: cty.List(cty.String), Required: false},
 		"temporary_os_disk_name":       &hcldec.AttrSpec{Name: "temporary_os_disk_name", Type: cty.String, Required: false},
 		"os_disk_size_gb":              &hcldec.AttrSpec{Name: "os_disk_size_gb", Type: cty.Number, Required: false},

builder/hyperone/config.hcl2spec.go

@@ -174,7 +174,7 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"chroot_disk_size":             &hcldec.AttrSpec{Name: "chroot_disk_size", Type: cty.Number, Required: false},
 		"chroot_disk_type":             &hcldec.AttrSpec{Name: "chroot_disk_type", Type: cty.String, Required: false},
 		"chroot_mount_path":            &hcldec.AttrSpec{Name: "chroot_mount_path", Type: cty.String, Required: false},
-		"chroot_mounts":                &hcldec.BlockListSpec{TypeName: "chroot_mounts", Nested: &hcldec.AttrSpec{Name: "chroot_mounts", Type: cty.List(cty.String), Required: false}},
+		"chroot_mounts":                &hcldec.AttrSpec{Name: "chroot_mounts", Type: cty.List(cty.List(cty.String)), Required: false},
 		"chroot_copy_files":            &hcldec.AttrSpec{Name: "chroot_copy_files", Type: cty.List(cty.String), Required: false},
 		"chroot_command_wrapper":       &hcldec.AttrSpec{Name: "chroot_command_wrapper", Type: cty.String, Required: false},
 		"mount_options":                &hcldec.AttrSpec{Name: "mount_options", Type: cty.List(cty.String), Required: false},

builder/osc/chroot/builder.hcl2spec.go

@@ -103,7 +103,7 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"secret_key":                 &hcldec.AttrSpec{Name: "secret_key", Type: cty.String, Required: false},
 		"skip_metadata_api_check":    &hcldec.AttrSpec{Name: "skip_metadata_api_check", Type: cty.Bool, Required: false},
 		"token":                      &hcldec.AttrSpec{Name: "token", Type: cty.String, Required: false},
-		"chroot_mounts":              &hcldec.BlockListSpec{TypeName: "chroot_mounts", Nested: &hcldec.AttrSpec{Name: "chroot_mounts", Type: cty.List(cty.String), Required: false}},
+		"chroot_mounts":              &hcldec.AttrSpec{Name: "chroot_mounts", Type: cty.List(cty.List(cty.String)), Required: false},
 		"command_wrapper":            &hcldec.AttrSpec{Name: "command_wrapper", Type: cty.String, Required: false},
 		"copy_files":                 &hcldec.AttrSpec{Name: "copy_files", Type: cty.List(cty.String), Required: false},
 		"device_path":                &hcldec.AttrSpec{Name: "device_path", Type: cty.String, Required: false},

builder/parallels/iso/builder.hcl2spec.go

@@ -135,8 +135,8 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"memory":                       &hcldec.AttrSpec{Name: "memory", Type: cty.Number, Required: false},
 		"sound":                        &hcldec.AttrSpec{Name: "sound", Type: cty.Bool, Required: false},
 		"usb":                          &hcldec.AttrSpec{Name: "usb", Type: cty.Bool, Required: false},
-		"prlctl":                       &hcldec.BlockListSpec{TypeName: "prlctl", Nested: &hcldec.AttrSpec{Name: "prlctl", Type: cty.List(cty.String), Required: false}},
+		"prlctl":                       &hcldec.AttrSpec{Name: "prlctl", Type: cty.List(cty.List(cty.String)), Required: false},
-		"prlctl_post":                  &hcldec.BlockListSpec{TypeName: "prlctl_post", Nested: &hcldec.AttrSpec{Name: "prlctl_post", Type: cty.List(cty.String), Required: false}},
+		"prlctl_post":                  &hcldec.AttrSpec{Name: "prlctl_post", Type: cty.List(cty.List(cty.String)), Required: false},
 		"prlctl_version_file":          &hcldec.AttrSpec{Name: "prlctl_version_file", Type: cty.String, Required: false},
 		"shutdown_command":             &hcldec.AttrSpec{Name: "shutdown_command", Type: cty.String, Required: false},
 		"shutdown_timeout":             &hcldec.AttrSpec{Name: "shutdown_timeout", Type: cty.String, Required: false},

builder/parallels/pvm/config.hcl2spec.go

@@ -101,8 +101,8 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"floppy_dirs":                  &hcldec.AttrSpec{Name: "floppy_dirs", Type: cty.List(cty.String), Required: false},
 		"floppy_label":                 &hcldec.AttrSpec{Name: "floppy_label", Type: cty.String, Required: false},
 		"output_directory":             &hcldec.AttrSpec{Name: "output_directory", Type: cty.String, Required: false},
-		"prlctl":                       &hcldec.BlockListSpec{TypeName: "prlctl", Nested: &hcldec.AttrSpec{Name: "prlctl", Type: cty.List(cty.String), Required: false}},
+		"prlctl":                       &hcldec.AttrSpec{Name: "prlctl", Type: cty.List(cty.List(cty.String)), Required: false},
-		"prlctl_post":                  &hcldec.BlockListSpec{TypeName: "prlctl_post", Nested: &hcldec.AttrSpec{Name: "prlctl_post", Type: cty.List(cty.String), Required: false}},
+		"prlctl_post":                  &hcldec.AttrSpec{Name: "prlctl_post", Type: cty.List(cty.List(cty.String)), Required: false},
 		"prlctl_version_file":          &hcldec.AttrSpec{Name: "prlctl_version_file", Type: cty.String, Required: false},
 		"communicator":                 &hcldec.AttrSpec{Name: "communicator", Type: cty.String, Required: false},
 		"pause_before_connecting":      &hcldec.AttrSpec{Name: "pause_before_connecting", Type: cty.String, Required: false},

builder/qemu/builder.hcl2spec.go

@@ -210,7 +210,7 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"memory":                       &hcldec.AttrSpec{Name: "memory", Type: cty.Number, Required: false},
 		"net_device":                   &hcldec.AttrSpec{Name: "net_device", Type: cty.String, Required: false},
 		"output_directory":             &hcldec.AttrSpec{Name: "output_directory", Type: cty.String, Required: false},
-		"qemuargs":                     &hcldec.BlockListSpec{TypeName: "qemuargs", Nested: &hcldec.AttrSpec{Name: "qemuargs", Type: cty.List(cty.String), Required: false}},
+		"qemuargs":                     &hcldec.AttrSpec{Name: "qemuargs", Type: cty.List(cty.List(cty.String)), Required: false},
 		"qemu_binary":                  &hcldec.AttrSpec{Name: "qemu_binary", Type: cty.String, Required: false},
 		"qmp_enable":                   &hcldec.AttrSpec{Name: "qmp_enable", Type: cty.Bool, Required: false},
 		"qmp_socket_path":              &hcldec.AttrSpec{Name: "qmp_socket_path", Type: cty.String, Required: false},

builder/virtualbox/iso/builder.hcl2spec.go

@@ -215,8 +215,8 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"memory":                       &hcldec.AttrSpec{Name: "memory", Type: cty.Number, Required: false},
 		"sound":                        &hcldec.AttrSpec{Name: "sound", Type: cty.String, Required: false},
 		"usb":                          &hcldec.AttrSpec{Name: "usb", Type: cty.Bool, Required: false},
-		"vboxmanage":                   &hcldec.BlockListSpec{TypeName: "vboxmanage", Nested: &hcldec.AttrSpec{Name: "vboxmanage", Type: cty.List(cty.String), Required: false}},
+		"vboxmanage":                   &hcldec.AttrSpec{Name: "vboxmanage", Type: cty.List(cty.List(cty.String)), Required: false},
-		"vboxmanage_post":              &hcldec.BlockListSpec{TypeName: "vboxmanage_post", Nested: &hcldec.AttrSpec{Name: "vboxmanage_post", Type: cty.List(cty.String), Required: false}},
+		"vboxmanage_post":              &hcldec.AttrSpec{Name: "vboxmanage_post", Type: cty.List(cty.List(cty.String)), Required: false},
 		"virtualbox_version_file":      &hcldec.AttrSpec{Name: "virtualbox_version_file", Type: cty.String, Required: false},
 		"bundle_iso":                   &hcldec.AttrSpec{Name: "bundle_iso", Type: cty.Bool, Required: false},
 		"guest_additions_mode":         &hcldec.AttrSpec{Name: "guest_additions_mode", Type: cty.String, Required: false},

builder/virtualbox/ovf/config.hcl2spec.go

@@ -190,8 +190,8 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"post_shutdown_delay":          &hcldec.AttrSpec{Name: "post_shutdown_delay", Type: cty.String, Required: false},
 		"disable_shutdown":             &hcldec.AttrSpec{Name: "disable_shutdown", Type: cty.Bool, Required: false},
 		"acpi_shutdown":                &hcldec.AttrSpec{Name: "acpi_shutdown", Type: cty.Bool, Required: false},
-		"vboxmanage":                   &hcldec.BlockListSpec{TypeName: "vboxmanage", Nested: &hcldec.AttrSpec{Name: "vboxmanage", Type: cty.List(cty.String), Required: false}},
+		"vboxmanage":                   &hcldec.AttrSpec{Name: "vboxmanage", Type: cty.List(cty.List(cty.String)), Required: false},
-		"vboxmanage_post":              &hcldec.BlockListSpec{TypeName: "vboxmanage_post", Nested: &hcldec.AttrSpec{Name: "vboxmanage_post", Type: cty.List(cty.String), Required: false}},
+		"vboxmanage_post":              &hcldec.AttrSpec{Name: "vboxmanage_post", Type: cty.List(cty.List(cty.String)), Required: false},
 		"virtualbox_version_file":      &hcldec.AttrSpec{Name: "virtualbox_version_file", Type: cty.String, Required: false},
 		"guest_additions_mode":         &hcldec.AttrSpec{Name: "guest_additions_mode", Type: cty.String, Required: false},
 		"checksum":                     &hcldec.AttrSpec{Name: "checksum", Type: cty.String, Required: false},

builder/virtualbox/vm/config.hcl2spec.go

@@ -186,8 +186,8 @@ func (*FlatConfig) HCL2Spec() map[string]hcldec.Spec {
 		"post_shutdown_delay":          &hcldec.AttrSpec{Name: "post_shutdown_delay", Type: cty.String, Required: false},
 		"disable_shutdown":             &hcldec.AttrSpec{Name: "disable_shutdown", Type: cty.Bool, Required: false},
 		"acpi_shutdown":                &hcldec.AttrSpec{Name: "acpi_shutdown", Type: cty.Bool, Required: false},
-		"vboxmanage":                   &hcldec.BlockListSpec{TypeName: "vboxmanage", Nested: &hcldec.AttrSpec{Name: "vboxmanage", Type: cty.List(cty.String), Required: false}},
+		"vboxmanage":                   &hcldec.AttrSpec{Name: "vboxmanage", Type: cty.List(cty.List(cty.String)), Required: false},
-		"vboxmanage_post":              &hcldec.BlockListSpec{TypeName: "vboxmanage_post", Nested: &hcldec.AttrSpec{Name: "vboxmanage_post", Type: cty.List(cty.String), Required: false}},
+		"vboxmanage_post":              &hcldec.AttrSpec{Name: "vboxmanage_post", Type: cty.List(cty.List(cty.String)), Required: false},
 		"virtualbox_version_file":      &hcldec.AttrSpec{Name: "virtualbox_version_file", Type: cty.String, Required: false},
 		"guest_additions_mode":         &hcldec.AttrSpec{Name: "guest_additions_mode", Type: cty.String, Required: false},
 		"guest_additions_path":         &hcldec.AttrSpec{Name: "guest_additions_path", Type: cty.String, Required: false},

cmd/mapstructure-to-hcl2/mapstructure-to-hcl2.go

@@ -201,6 +201,10 @@ type StructDef struct {
 	Struct             *types.Struct
 }
 
+// outputStructHCL2SpecBody writes the map[string]hcldec.Spec that defines the HCL spec of a
+// struct. Based on the layout of said struct.
+// If a field of s is a struct then the HCL2Spec() function of that struct will be called, otherwise a
+// cty.Type is outputed.
 func outputStructHCL2SpecBody(w io.Writer, s *types.Struct) {
 	fmt.Fprintf(w, "s := map[string]hcldec.Spec{\n")
 
@@ -217,72 +221,99 @@ func outputStructHCL2SpecBody(w io.Writer, s *types.Struct) {
 	fmt.Fprintln(w, `return s`)
 }
 
+// outputHCL2SpecField is called on each field of a struct.
+// outputHCL2SpecField writes the values of the `map[string]hcldec.Spec` map
+// supposed to define the HCL spec of a struct.
 func outputHCL2SpecField(w io.Writer, accessor string, fieldType types.Type, tag *structtag.Tags) {
 	if m2h, err := tag.Get(""); err == nil && m2h.HasOption("self-defined") {
 		fmt.Fprintf(w, `(&%s{}).HCL2Spec()`, fieldType.String())
 		return
 	}
+	spec, _ := writeSpecField(accessor, fieldType)
+	switch spec := spec.(type) {
+	case string:
+		fmt.Fprintf(w, spec)
+	default:
+		fmt.Fprintf(w, `%#v`, spec)
+	}
+
+}
+
+// goFieldToCtyType is a recursive method that returns a cty.Type (or a string) based on the fieldType.
+// goFieldToCtyType returns the values of the `map[string]hcldec.Spec` map
+// supposed to define the HCL spec of a struct.
+// To allow it to be recursive, the method returns two values: an interface that can either be
+// a cty.Type or a string. The second argument is used for recursion and is the
+// type that will be used by the parent. For example when fieldType is a []string; a
+// recursive goFieldToCtyType call will return a cty.String.
+func writeSpecField(accessor string, fieldType types.Type) (interface{}, cty.Type) {
 	switch f := fieldType.(type) {
 	case *types.Pointer:
-		outputHCL2SpecField(w, accessor, f.Elem(), tag)
+		return writeSpecField(accessor, f.Elem())
 	case *types.Basic:
-		fmt.Fprintf(w, `%#v`, &hcldec.AttrSpec{
+		ctyType := basicKindToCtyType(f.Kind())
+		return &hcldec.AttrSpec{
 			Name:     accessor,
-			Type:     basicKindToCtyType(f.Kind()),
+			Type:     ctyType,
 			Required: false,
-		})
+		}, ctyType
 	case *types.Map:
-		fmt.Fprintf(w, `%#v`, &hcldec.BlockAttrsSpec{
+		return &hcldec.BlockAttrsSpec{
 			TypeName:    accessor,
 			ElementType: cty.String, // for now everything can be simplified to a map[string]string
 			Required:    false,
-		})
+		}, cty.Map(cty.String)
+	case *types.Named:
+		// Named is the relative type when of a field with a struct.
+		// E.g. SourceAmiFilter    *common.FlatAmiFilterOptions
+		// SourceAmiFilter will become a block with nested elements from the struct itself.
+		underlyingType := f.Underlying()
+		switch underlyingType.(type) {
+		case *types.Struct:
+			// A struct returns NilType because its HCL2Spec is written in the related file
+			// and we don't need to write it again.
+			return fmt.Sprintf(`&hcldec.BlockSpec{TypeName: "%s",`+
+				` Nested: hcldec.ObjectSpec((*%s)(nil).HCL2Spec())}`, accessor, f.String()), cty.NilType
+		default:
+			return writeSpecField(accessor, underlyingType)
+		}
 	case *types.Slice:
 		elem := f.Elem()
 		if ptr, isPtr := elem.(*types.Pointer); isPtr {
 			elem = ptr.Elem()
 		}
 		switch elem := elem.(type) {
-		case *types.Basic:
-			fmt.Fprintf(w, `%#v`, &hcldec.AttrSpec{
-				Name:     accessor,
-				Type:     cty.List(basicKindToCtyType(elem.Kind())),
-				Required: false,
-			})
 		case *types.Named:
+			// A Slice of Named is the relative type of a filed with a slice of structs.
+			// E.g. LaunchMappings []common.FlatBlockDevice
+			// LaunchMappings will validate more than one block with nested elements.
 			b := bytes.NewBuffer(nil)
 			underlyingType := elem.Underlying()
 			switch underlyingType.(type) {
 			case *types.Struct:
 				fmt.Fprintf(b, `hcldec.ObjectSpec((*%s)(nil).HCL2Spec())`, elem.String())
-			default:
-				outputHCL2SpecField(b, accessor, elem, tag)
 			}
-			fmt.Fprintf(w, `&hcldec.BlockListSpec{TypeName: "%s", Nested: %s}`, accessor, b.String())
+			return fmt.Sprintf(`&hcldec.BlockListSpec{TypeName: "%s", Nested: %s}`, accessor, b.String()), cty.NilType
-		case *types.Slice:
+		default:
+			_, specType := writeSpecField(accessor, elem)
+			if specType == cty.NilType {
+				return writeSpecField(accessor, elem.Underlying())
+			}
+			return &hcldec.AttrSpec{
+				Name:     accessor,
+				Type:     cty.List(specType),
+				Required: false,
+			}, cty.List(specType)
+		}
+	}
 	b := bytes.NewBuffer(nil)
-			outputHCL2SpecField(b, accessor, elem.Underlying(), tag)
+	fmt.Fprintf(b, `%#v`, &hcldec.AttrSpec{
-			fmt.Fprintf(w, `&hcldec.BlockListSpec{TypeName: "%s", Nested: %s}`, accessor, b.String())
-		default:
-			outputHCL2SpecField(w, accessor, elem.Underlying(), tag)
-		}
-	case *types.Named:
-		underlyingType := f.Underlying()
-		switch underlyingType.(type) {
-		case *types.Struct:
-			fmt.Fprintf(w, `&hcldec.BlockSpec{TypeName: "%s",`+
-				` Nested: hcldec.ObjectSpec((*%s)(nil).HCL2Spec())}`, accessor, f.String())
-		default:
-			outputHCL2SpecField(w, accessor, underlyingType, tag)
-		}
-	default:
-		fmt.Fprintf(w, `%#v`, &hcldec.AttrSpec{
 		Name:     accessor,
 		Type:     basicKindToCtyType(types.Bool),
 		Required: false,
 	})
-		fmt.Fprintf(w, `/* TODO(azr): could not find type */`)
+	fmt.Fprintf(b, `/* TODO(azr): could not find type */`)
-	}
+	return b.String(), cty.NilType
 }
 
 func basicKindToCtyType(kind types.BasicKind) cty.Type {

hcl2template/common_test.go

@@ -194,6 +194,10 @@ var (
 			"b",
 			"c",
 		},
+		SliceSliceString: [][]string{
+			{"a", "b"},
+			{"c", "d"},
+		},
 	}
 
 	basicMockBuilder = &MockBuilder{

hcl2template/mock.go

@@ -20,6 +20,7 @@ type NestedMockConfig struct {
 	Duration             time.Duration        `mapstructure:"duration"`
 	MapStringString      map[string]string    `mapstructure:"map_string_string"`
 	SliceString          []string             `mapstructure:"slice_string"`
+	SliceSliceString     [][]string           `mapstructure:"slice_slice_string"`
 	NamedMapStringString NamedMapStringString `mapstructure:"named_map_string_string"`
 	NamedString          NamedString          `mapstructure:"named_string"`
 }

hcl2template/mock.hcl2spec.go

@@ -17,6 +17,7 @@ type FlatMockConfig struct {
 	Duration             *string                `mapstructure:"duration" cty:"duration"`
 	MapStringString      map[string]string      `mapstructure:"map_string_string" cty:"map_string_string"`
 	SliceString          []string               `mapstructure:"slice_string" cty:"slice_string"`
+	SliceSliceString     [][]string             `mapstructure:"slice_slice_string" cty:"slice_slice_string"`
 	NamedMapStringString NamedMapStringString   `mapstructure:"named_map_string_string" cty:"named_map_string_string"`
 	NamedString          *NamedString           `mapstructure:"named_string" cty:"named_string"`
 	Nested               *FlatNestedMockConfig  `mapstructure:"nested" cty:"nested"`
@@ -43,6 +44,7 @@ func (*FlatMockConfig) HCL2Spec() map[string]hcldec.Spec {
 		"duration":                &hcldec.AttrSpec{Name: "duration", Type: cty.String, Required: false},
 		"map_string_string":       &hcldec.BlockAttrsSpec{TypeName: "map_string_string", ElementType: cty.String, Required: false},
 		"slice_string":            &hcldec.AttrSpec{Name: "slice_string", Type: cty.List(cty.String), Required: false},
+		"slice_slice_string":      &hcldec.AttrSpec{Name: "slice_slice_string", Type: cty.List(cty.List(cty.String)), Required: false},
 		"named_map_string_string": &hcldec.BlockAttrsSpec{TypeName: "named_map_string_string", ElementType: cty.String, Required: false},
 		"named_string":            &hcldec.AttrSpec{Name: "named_string", Type: cty.String, Required: false},
 		"nested":                  &hcldec.BlockSpec{TypeName: "nested", Nested: hcldec.ObjectSpec((*FlatNestedMockConfig)(nil).HCL2Spec())},
@@ -62,6 +64,7 @@ type FlatNestedMockConfig struct {
 	Duration             *string              `mapstructure:"duration" cty:"duration"`
 	MapStringString      map[string]string    `mapstructure:"map_string_string" cty:"map_string_string"`
 	SliceString          []string             `mapstructure:"slice_string" cty:"slice_string"`
+	SliceSliceString     [][]string           `mapstructure:"slice_slice_string" cty:"slice_slice_string"`
 	NamedMapStringString NamedMapStringString `mapstructure:"named_map_string_string" cty:"named_map_string_string"`
 	NamedString          *NamedString         `mapstructure:"named_string" cty:"named_string"`
 }
@@ -86,6 +89,7 @@ func (*FlatNestedMockConfig) HCL2Spec() map[string]hcldec.Spec {
 		"duration":                &hcldec.AttrSpec{Name: "duration", Type: cty.String, Required: false},
 		"map_string_string":       &hcldec.BlockAttrsSpec{TypeName: "map_string_string", ElementType: cty.String, Required: false},
 		"slice_string":            &hcldec.AttrSpec{Name: "slice_string", Type: cty.List(cty.String), Required: false},
+		"slice_slice_string":      &hcldec.AttrSpec{Name: "slice_slice_string", Type: cty.List(cty.List(cty.String)), Required: false},
 		"named_map_string_string": &hcldec.BlockAttrsSpec{TypeName: "named_map_string_string", ElementType: cty.String, Required: false},
 		"named_string":            &hcldec.AttrSpec{Name: "named_string", Type: cty.String, Required: false},
 	}

hcl2template/testdata/build/basic.pkr.hcl

@@ -22,6 +22,10 @@ build {
             "b",
             "c",
         ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
 
         nested {
             string   = "string"
@@ -39,6 +43,10 @@ build {
                 "b",
                 "c",
             ]
+            slice_slice_string = [
+                ["a","b"],
+                ["c","d"]
+            ]
         }
 
         nested_slice {
@@ -61,6 +69,10 @@ build {
             "b",
             "c",
         ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
 
         nested {
             string   = "string"
@@ -78,6 +90,10 @@ build {
                 "b",
                 "c",
             ]
+            slice_slice_string = [
+                ["a","b"],
+                ["c","d"]
+            ]
         }
 
         nested_slice {
@@ -100,6 +116,10 @@ build {
             "b",
             "c",
         ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
 
         nested {
             string   = "string"
@@ -117,6 +137,10 @@ build {
                 "b",
                 "c",
             ]
+            slice_slice_string = [
+                ["a","b"],
+                ["c","d"]
+            ]
         }
 
         nested_slice {

hcl2template/testdata/complete/build.pkr.hcl

@@ -22,6 +22,10 @@ build {
             "b",
             "c",
         ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
 
         nested {
             string   = "string"
@@ -39,6 +43,10 @@ build {
                 "b",
                 "c",
             ]
+            slice_slice_string = [
+                ["a","b"],
+                ["c","d"]
+            ]
         }
 
         nested_slice {
@@ -61,6 +69,10 @@ build {
             "b",
             "c",
         ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
 
         nested {
             string   = "string"
@@ -78,6 +90,10 @@ build {
                 "b",
                 "c",
             ]
+            slice_slice_string = [
+                ["a","b"],
+                ["c","d"]
+            ]
         }
 
         nested_slice {
@@ -101,6 +117,10 @@ build {
             "b",
             "c",
         ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
 
         nested {
             string   = "string"
@@ -118,6 +138,10 @@ build {
                 "b",
                 "c",
             ]
+            slice_slice_string = [
+                ["a","b"],
+                ["c","d"]
+            ]
         }
 
         nested_slice {
@@ -140,6 +164,10 @@ build {
             "b",
             "c",
         ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
 
         nested {
             string   = "string"
@@ -157,6 +185,10 @@ build {
                 "b",
                 "c",
             ]
+            slice_slice_string = [
+                ["a","b"],
+                ["c","d"]
+            ]
         }
 
         nested_slice {

hcl2template/testdata/complete/sources.pkr.hcl

@@ -14,6 +14,10 @@ source "virtualbox-iso" "ubuntu-1204" {
         "b",
         "c",
     ]
+    slice_slice_string = [
+        ["a","b"],
+        ["c","d"]
+    ]
 
     nested {
         string   = "string"
@@ -31,23 +35,9 @@ source "virtualbox-iso" "ubuntu-1204" {
             "b",
             "c",
         ]
-    }
+        slice_slice_string = [
-
+            ["a","b"],
-    nested_slice {
+            ["c","d"]
-        string   = "string"
-        int      = 42
-        int64    = 43
-        bool     = true
-        trilean  = true
-        duration = "10s"
-        map_string_string {
-            a = "b"
-            c = "d"
-        }
-        slice_string = [
-            "a",
-            "b",
-            "c",
         ]
     }
 
@@ -67,5 +57,31 @@ source "virtualbox-iso" "ubuntu-1204" {
             "b",
             "c",
         ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
+    }
+
+    nested_slice {
+        string   = "string"
+        int      = 42
+        int64    = 43
+        bool     = true
+        trilean  = true
+        duration = "10s"
+        map_string_string {
+            a = "b"
+            c = "d"
+        }
+        slice_string = [
+            "a",
+            "b",
+            "c",
+        ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
     }
 }

hcl2template/testdata/sources/basic.pkr.hcl

@@ -15,6 +15,10 @@ source "virtualbox-iso" "ubuntu-1204" {
         "b",
         "c",
     ]
+    slice_slice_string = [
+        ["a","b"],
+        ["c","d"]
+    ]
 
     nested {
         string   = "string"
@@ -32,23 +36,9 @@ source "virtualbox-iso" "ubuntu-1204" {
             "b",
             "c",
         ]
-    }
+        slice_slice_string = [
-
+            ["a","b"],
-    nested_slice {
+            ["c","d"]
-        string   = "string"
-        int      = 42
-        int64    = 43
-        bool     = true
-        trilean  = true
-        duration = "10s"
-        map_string_string {
-            a = "b"
-            c = "d"
-        }
-        slice_string = [
-            "a",
-            "b",
-            "c",
         ]
     }
 
@@ -68,5 +58,31 @@ source "virtualbox-iso" "ubuntu-1204" {
             "b",
             "c",
         ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
+    }
+
+    nested_slice {
+        string   = "string"
+        int      = 42
+        int64    = 43
+        bool     = true
+        trilean  = true
+        duration = "10s"
+        map_string_string {
+            a = "b"
+            c = "d"
+        }
+        slice_string = [
+            "a",
+            "b",
+            "c",
+        ]
+        slice_slice_string = [
+            ["a","b"],
+            ["c","d"]
+        ]
     }
 }