Initial stab at JSON plan output

command/plan.go

@@ -16,7 +16,7 @@ type PlanCommand struct {
 }
 
 func (c *PlanCommand) Run(args []string) int {
-	var destroy, refresh, detailed bool
+	var destroy, refresh, detailed, outJson bool
 	var outPath string
 	var moduleDepth int
 
@@ -27,6 +27,7 @@ func (c *PlanCommand) Run(args []string) int {
 	cmdFlags.BoolVar(&refresh, "refresh", true, "refresh")
 	c.addModuleDepthFlag(cmdFlags, &moduleDepth)
 	cmdFlags.StringVar(&outPath, "out", "", "path")
+	cmdFlags.BoolVar(&outJson, "out-json", false, "out-json")
 	cmdFlags.StringVar(&c.Meta.statePath, "state", DefaultStateFilename, "path")
 	cmdFlags.StringVar(&c.Meta.backupPath, "backup", "", "path")
 	cmdFlags.BoolVar(&detailed, "detailed-exitcode", false, "detailed-exitcode")
@@ -111,7 +112,11 @@ func (c *PlanCommand) Run(args []string) int {
 		f, err := os.Create(outPath)
 		if err == nil {
 			defer f.Close()
-			err = terraform.WritePlan(plan, f)
+			if outJson {
+				err = terraform.WriteJsonPlan(plan, f)
+			} else {
+				err = terraform.WritePlan(plan, f)
+			}
 		}
 		if err != nil {
 			c.Ui.Error(fmt.Sprintf("Error writing plan file: %s", err))

terraform/diff.go

@@ -124,9 +124,11 @@ func (d *Diff) init() {
 // ModuleDiff tracks the differences between resources to apply within
 // a single module.
 type ModuleDiff struct {
-	Path      []string
-	Resources map[string]*InstanceDiff
-	Destroy   bool // Set only by the destroy plan
+	Path      []string                 `json:"path"`
+	Resources map[string]*InstanceDiff `json:"resources"`
+
+	// Set only by the destroy plan
+	Destroy bool `json:"destroy"`
 }
 
 func (d *ModuleDiff) init() {
@@ -270,20 +272,20 @@ func (d *ModuleDiff) String() string {
 
 // InstanceDiff is the diff of a resource from some state to another.
 type InstanceDiff struct {
-	Attributes     map[string]*ResourceAttrDiff
-	Destroy        bool
-	DestroyTainted bool
+	Attributes     map[string]*ResourceAttrDiff `json:"attributes"`
+	Destroy        bool                         `json:"destroy"`
+	DestroyTainted bool                         `json:"tainted"`
 }
 
 // ResourceAttrDiff is the diff of a single attribute of a resource.
 type ResourceAttrDiff struct {
-	Old         string      // Old Value
-	New         string      // New Value
-	NewComputed bool        // True if new value is computed (unknown currently)
-	NewRemoved  bool        // True if this attribute is being removed
-	NewExtra    interface{} // Extra information for the provider
-	RequiresNew bool        // True if change requires new resource
-	Type        DiffAttrType
+	Old         string       `json:"old"`          // Old Value
+	New         string       `json:"new"`          // New Value
+	NewComputed bool         `json:"new_computed"` // True if new value is computed (unknown currently)
+	NewRemoved  bool         `json:"new_removed"`  // True if this attribute is being removed
+	NewExtra    interface{}  `json:"new_extra"`    // Extra information for the provider
+	RequiresNew bool         `json:"requires_new"` // True if change requires new resource
+	Type        DiffAttrType `json:"-"`
 }
 
 func (d *ResourceAttrDiff) GoString() string {

terraform/plan.go

@@ -3,6 +3,7 @@ package terraform
 import (
 	"bytes"
 	"encoding/gob"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -115,6 +116,23 @@ func ReadPlan(src io.Reader) (*Plan, error) {
 	return result, nil
 }
 
+// WriteJsonPlan writes a plan somewhere in a JSON format.
+func WriteJsonPlan(d *Plan, dst io.Writer) error {
+
+	// Encode the data in a human-friendly way
+	data, err := json.MarshalIndent(d.Diff.Modules, "", "    ")
+	if err != nil {
+		return err
+	}
+
+	// We append a newline to the data because MarshalIndent doesn't
+	data = append(data, '\n')
+
+	_, err = dst.Write(data)
+
+	return err
+}
+
 // WritePlan writes a plan somewhere in a binary format.
 func WritePlan(d *Plan, dst io.Writer) error {
 	// Write the magic bytes so we can determine the file format later