config/configschema: stub out initial API

config/configschema/decoder_spec.go

@@ -0,0 +1,16 @@
+package configschema
+
+import (
+	"github.com/hashicorp/hcl2/hcldec"
+)
+
+// DecoderSpec returns a zcldec.Spec that can be used to decode a zcl Body
+// using the facilities in the zcldec package.
+//
+// The returned specification is guaranteed to return a value of the same type
+// returned by method ImpliedType, but it may contain null or unknown values if
+// any of the block attributes are defined as optional and/or computed
+// respectively.
+func (b *Block) DecoderSpec() hcldec.Spec {
+	return nil
+}

config/configschema/doc.go

@@ -0,0 +1,14 @@
+// Package configschema contains types for describing the expected structure
+// of a configuration block whose shape is not known until runtime.
+//
+// For example, this is used to describe the expected contents of a resource
+// configuration block, which is defined by the corresponding provider plugin
+// and thus not compiled into Terraform core.
+//
+// A configschema primarily describes the shape of configuration, but it is
+// also suitable for use with other structures derived from the configuration,
+// such as the cached state of a resource or a resource diff.
+//
+// This package should not be confused with the package helper/schema, which
+// is the higher-level helper library used to implement providers themselves.
+package configschema

config/configschema/implied_type.go

@@ -0,0 +1,16 @@
+package configschema
+
+import (
+	"github.com/zclconf/go-cty/cty"
+)
+
+// ImpliedType returns the cty.Type that would result from decoding a
+// configuration block using the receiving block schema.
+//
+// ImpliedType always returns a result, even if the given schema is
+// inconsistent. Code that creates configschema.Block objects should be
+// tested using the InternalValidate method to detect any inconsistencies
+// that would cause this method to fall back on defaults and assumptions.
+func (b *Block) ImpliedType() cty.Type {
+	return cty.DynamicPseudoType
+}

config/configschema/nestingmode_string.go

@@ -0,0 +1,16 @@
+// Code generated by "stringer -type=NestingMode"; DO NOT EDIT.
+
+package configschema
+
+import "fmt"
+
+const _NestingMode_name = "nestingModeInvalidNestingSingleNestingListNestingSetNestingMap"
+
+var _NestingMode_index = [...]uint8{0, 18, 31, 42, 52, 62}
+
+func (i NestingMode) String() string {
+	if i < 0 || i >= NestingMode(len(_NestingMode_index)-1) {
+		return fmt.Sprintf("NestingMode(%d)", i)
+	}
+	return _NestingMode_name[_NestingMode_index[i]:_NestingMode_index[i+1]]
+}

config/configschema/schema.go

@@ -0,0 +1,87 @@
+package configschema
+
+import (
+	"github.com/zclconf/go-cty/cty"
+)
+
+// Block represents a configuration block.
+//
+// "Block" here is a logical grouping construct, though it happens to map
+// directly onto the physical block syntax of Terraform's native configuration
+// syntax. It may be a more a matter of convention in other syntaxes, such as
+// JSON.
+//
+// When converted to a value, a Block always becomes an instance of an object
+// type derived from its defined attributes and nested blocks
+type Block struct {
+	// Attributes describes any attributes that may appear directly inside
+	// the block.
+	Attributes map[string]*Attribute
+
+	// BlockTypes describes any nested block types that may appear directly
+	// inside the block.
+	BlockTypes map[string]*NestedBlock
+}
+
+// Attribute represents a configuration attribute, within a block.
+type Attribute struct {
+	// Type is a type specification that the attribute's value must conform to.
+	Type cty.Type
+
+	// Required, if set to true, specifies that an omitted or null value is
+	// not permitted.
+	Required bool
+
+	// Optional, if set to true, specifies that an omitted or null value is
+	// permitted. This field conflicts with Required.
+	Optional bool
+
+	// Computed, if set to true, specifies that the value comes from the
+	// provider rather than from configuration. If combined with Optional,
+	// then the config may optionally provide an overridden value.
+	Computed bool
+}
+
+// NestedBlock represents the embedding of one block within another.
+type NestedBlock struct {
+	// Block is the description of the block that's nested.
+	Block
+
+	// Nesting provides the nesting mode for the child block, which determines
+	// how many instances of the block are allowed, how many labels it expects,
+	// and how the resulting data will be converted into a data structure.
+	Nesting NestingMode
+}
+
+// NestingMode is an enumeration of modes for nesting blocks inside other
+// blocks.
+type NestingMode int
+
+//go:generate stringer -type=NestingMode
+
+const (
+	nestingModeInvalid NestingMode = iota
+
+	// NestingSingle indicates that only a single instance of a given
+	// block type is permitted, with no labels, and its content should be
+	// provided directly as an object value.
+	NestingSingle
+
+	// NestingList indicates that multiple blocks of the given type are
+	// permitted, with no labels, and that their corresponding objects should
+	// be provided in a list.
+	NestingList
+
+	// NestingSet indicates that multiple blocks of the given type are
+	// permitted, with no labels, and that their corresponding objects should
+	// be provided in a set.
+	NestingSet
+
+	// NestingMap indicates that multiple blocks of the given type are
+	// permitted, each with a single label, and that their corresponding
+	// objects should be provided in a map whose keys are the labels.
+	//
+	// It's an error, therefore, to use the same label value on multiple
+	// blocks.
+	NestingMap
+)