json: start of low-level decoding

zcl/json/structure.go

@@ -1,6 +1,9 @@
 package json
 
 import (
+	"fmt"
+
+	"github.com/apparentlymart/go-cty/cty"
 	"github.com/apparentlymart/go-zcl/zcl"
 )
 
@@ -22,11 +25,157 @@ type expression struct {
 }
 
 func (b *body) Content(schema *zcl.BodySchema) (*zcl.BodyContent, zcl.Diagnostics) {
-	// TODO: Implement
-	return nil, nil
+	content, _, diags := b.PartialContent(schema)
+
+	// TODO: generate errors for the stuff we didn't use in PartialContent
+
+	return content, diags
 }
 
 func (b *body) PartialContent(schema *zcl.BodySchema) (*zcl.BodyContent, zcl.Body, zcl.Diagnostics) {
-	// TODO: Implement
-	return nil, nil, nil
+
+	obj := b.obj
+	jsonAttrs := obj.Attrs
+	usedNames := map[string]struct{}{}
+	if b.hiddenAttrs != nil {
+		for k := range b.hiddenAttrs {
+			usedNames[k] = struct{}{}
+		}
+	}
+	var diags zcl.Diagnostics
+
+	content := &zcl.BodyContent{
+		Attributes: map[string]*zcl.Attribute{},
+		Blocks:     nil,
+	}
+
+	for _, attrS := range schema.Attributes {
+		jsonAttr, exists := jsonAttrs[attrS.Name]
+		_, used := usedNames[attrS.Name]
+		if used || !exists {
+			if attrS.Required {
+				diags = diags.Append(&zcl.Diagnostic{
+					Severity: zcl.DiagError,
+					Summary:  "Missing required attribute",
+					Detail:   fmt.Sprintf("The attribute %q is required, so a JSON object property must be present with this name.", attrS.Name),
+					Subject:  &obj.OpenRange,
+				})
+			}
+			usedNames[attrS.Name] = struct{}{}
+			continue
+		}
+		content.Attributes[attrS.Name] = &zcl.Attribute{
+			Name:  attrS.Name,
+			Expr:  &expression{src: jsonAttr.Value},
+			Range: zcl.RangeBetween(jsonAttr.NameRange, jsonAttr.Value.Range()),
+		}
+		usedNames[attrS.Name] = struct{}{}
+	}
+
+	for _, blockS := range schema.Blocks {
+		jsonAttr, exists := jsonAttrs[blockS.Type]
+		_, used := usedNames[blockS.Type]
+		if used || !exists {
+			usedNames[blockS.Type] = struct{}{}
+			continue
+		}
+		v := jsonAttr.Value
+		diags = append(diags, b.unpackBlock(v, blockS.Type, &jsonAttr.NameRange, blockS.LabelNames, nil, nil, &content.Blocks)...)
+	}
+
+	unusedBody := &body{
+		obj:         b.obj,
+		hiddenAttrs: usedNames,
+	}
+
+	return content, unusedBody, diags
+}
+
+func (b *body) unpackBlock(v node, typeName string, typeRange *zcl.Range, labelsLeft []string, labelsUsed []string, labelRanges []zcl.Range, blocks *zcl.Blocks) (diags zcl.Diagnostics) {
+	if len(labelsLeft) > 0 {
+		labelName := labelsLeft[0]
+		ov, ok := v.(*objectVal)
+		if !ok {
+			diags = diags.Append(&zcl.Diagnostic{
+				Severity: zcl.DiagError,
+				Summary:  "Incorrect JSON value type",
+				Detail:   fmt.Sprintf("A JSON object is required, whose keys represent the %q block's %s.", typeName, labelName),
+				Subject:  v.StartRange().Ptr(),
+			})
+			return
+		}
+		labelsUsed := append(labelsUsed, "")
+		labelRanges := append(labelRanges, zcl.Range{})
+		for pk, p := range ov.Attrs {
+			labelsUsed[len(labelsUsed)-1] = pk
+			labelRanges[len(labelRanges)-1] = p.NameRange
+			diags = append(diags, b.unpackBlock(p.Value, typeName, typeRange, labelsLeft[1:], labelsUsed, labelRanges, blocks)...)
+		}
+		return
+	}
+
+	// By the time we get here, we've peeled off all the labels and we're ready
+	// to deal with the block's actual content.
+
+	// need to copy the label slices because their underlying arrays will
+	// continue to be mutated after we return.
+	labels := make([]string, len(labelsUsed))
+	copy(labels, labelsUsed)
+	labelR := make([]zcl.Range, len(labelRanges))
+	copy(labelR, labelRanges)
+
+	switch tv := v.(type) {
+	case *objectVal:
+		// Single instance of the block
+		*blocks = append(*blocks, &zcl.Block{
+			Type:   typeName,
+			Labels: labels,
+			Body: &body{
+				obj: tv,
+			},
+
+			DefRange:    tv.OpenRange,
+			TypeRange:   *typeRange,
+			LabelRanges: labelR,
+		})
+	case *arrayVal:
+		// Multiple instances of the block
+		for _, av := range tv.Values {
+			ov, ok := av.(*objectVal)
+			if !ok {
+				diags = diags.Append(&zcl.Diagnostic{
+					Severity: zcl.DiagError,
+					Summary:  "Incorrect JSON value type",
+					Detail:   fmt.Sprintf("A JSON object is required, representing the contents of a %q block.", typeName),
+					Subject:  v.StartRange().Ptr(),
+				})
+				continue
+			}
+
+			*blocks = append(*blocks, &zcl.Block{
+				Type:   typeName,
+				Labels: labels,
+				Body: &body{
+					obj: ov,
+				},
+
+				DefRange:    tv.OpenRange,
+				TypeRange:   *typeRange,
+				LabelRanges: labelR,
+			})
+		}
+	default:
+		diags = diags.Append(&zcl.Diagnostic{
+			Severity: zcl.DiagError,
+			Summary:  "Incorrect JSON value type",
+			Detail:   fmt.Sprintf("Either a JSON object or a JSON array is required, representing the contents of one or more %q blocks.", typeName),
+			Subject:  v.StartRange().Ptr(),
+		})
+	}
+	return
+}
+
+func (e *expression) LiteralValue() (cty.Value, zcl.Diagnostics) {
+	// TODO: Implement
+	return cty.NilVal, nil
 }

zcl/schema.go

@@ -1,15 +1,21 @@
 package zcl
 
-// ElementHeaderSchema represents the shape of an element header, and is
-// used for matching elements within bodies.
-type ElementHeaderSchema struct {
-	Name       string
+// BlockHeaderSchema represents the shape of a block header, and is
+// used for matching blocks within bodies.
+type BlockHeaderSchema struct {
+	Type       string
 	LabelNames []string
-	Single     bool
+}
+
+// AttributeSchema represents the requirements for an attribute, and is used
+// for matching attributes within bodies.
+type AttributeSchema struct {
+	Name     string
+	Required bool
 }
 
 // BodySchema represents the desired shallow structure of a body.
 type BodySchema struct {
-	Attributes []string
-	Elements   []ElementHeaderSchema
+	Attributes []AttributeSchema
+	Blocks     []BlockHeaderSchema
 }

zcl/structure.go

@@ -47,7 +47,7 @@ type Body interface {
 
 // BodyContent is the result of applying a BodySchema to a Body.
 type BodyContent struct {
-	Attributes map[string]Attribute
+	Attributes map[string]*Attribute
 	Blocks     Blocks
 }
 
@@ -64,7 +64,7 @@ type Attribute struct {
 // Expression is a literal value or an expression provided in the
 // configuration, which can be evaluated within a scope to produce a value.
 type Expression interface {
-	LiteralValue() cty.Value
+	LiteralValue() (cty.Value, Diagnostics)
 	// TODO: evaluation of non-literal expressions
 }