Support patching an ARM template.

Patching support is based on RFC 6902.  Users have the ability to patch
the ARM virtual machine template before it is submitted to Azure for
processing.

Add a dependency on evanphx/json-patch to support JSON patching.

builder/azure/arm/TestVirtualMachineDeployment05.approved.txt

@@ -27,7 +27,47 @@
   "resources": [
     {
       "apiVersion": "[variables('apiVersion')]",
+<<<<<<< b7954bc5d9bffce6f22085a3808dea6b48090ab6
       "dependsOn": [],
+=======
+      "location": "[variables('location')]",
+      "name": "[variables('publicIPAddressName')]",
+      "properties": {
+        "dnsSettings": {
+          "domainNameLabel": "[parameters('dnsNameForPublicIP')]"
+        },
+        "publicIPAllocationMethod": "[variables('publicIPAddressType')]"
+      },
+      "type": "Microsoft.Network/publicIPAddresses"
+    },
+    {
+      "apiVersion": "[variables('apiVersion')]",
+      "location": "[variables('location')]",
+      "name": "[variables('virtualNetworkName')]",
+      "properties": {
+        "addressSpace": {
+          "addressPrefixes": [
+            "[variables('addressPrefix')]"
+          ]
+        },
+        "subnets": [
+          {
+            "name": "[variables('subnetName')]",
+            "properties": {
+              "addressPrefix": "[variables('subnetAddressPrefix')]"
+            }
+          }
+        ]
+      },
+      "type": "Microsoft.Network/virtualNetworks"
+    },
+    {
+      "apiVersion": "[variables('apiVersion')]",
+      "dependsOn": [
+        "[concat('Microsoft.Network/publicIPAddresses/', variables('publicIPAddressName'))]",
+        "[concat('Microsoft.Network/virtualNetworks/', variables('virtualNetworkName'))]"
+      ],
+>>>>>>> Support patching an ARM template.
       "location": "[variables('location')]",
       "name": "[variables('nicName')]",
       "properties": {
@@ -36,6 +76,12 @@
             "name": "ipconfig",
             "properties": {
               "privateIPAllocationMethod": "Dynamic",
+<<<<<<< b7954bc5d9bffce6f22085a3808dea6b48090ab6
+=======
+              "publicIPAddress": {
+                "id": "[resourceId('Microsoft.Network/publicIPAddresses', variables('publicIPAddressName'))]"
+              },
+>>>>>>> Support patching an ARM template.
               "subnet": {
                 "id": "[variables('subnetRef')]"
               }
@@ -52,6 +98,14 @@
       ],
       "location": "[variables('location')]",
       "name": "[parameters('vmName')]",
+<<<<<<< b7954bc5d9bffce6f22085a3808dea6b48090ab6
+=======
+      "plan": {
+        "name": "MySKU",
+        "product": "MyOffer",
+        "publisher": "MyPublisher"
+      },
+>>>>>>> Support patching an ARM template.
       "properties": {
         "diagnosticsProfile": {
           "bootDiagnostics": {
@@ -110,11 +164,19 @@
     "publicIPAddressType": "Dynamic",
     "sshKeyPath": "[concat('/home/',parameters('adminUsername'),'/.ssh/authorized_keys')]",
     "subnetAddressPrefix": "10.0.0.0/24",
+<<<<<<< b7954bc5d9bffce6f22085a3808dea6b48090ab6
     "subnetName": "ignore",
     "subnetRef": "[concat(variables('vnetID'),'/subnets/',variables('subnetName'))]",
     "virtualNetworkName": "ignore",
     "virtualNetworkResourceGroup": "ignore",
     "vmStorageAccountContainerName": "images",
     "vnetID": "[resourceId(variables('virtualNetworkResourceGroup'), 'Microsoft.Network/virtualNetworks', variables('virtualNetworkName'))]"
+=======
+    "subnetName": "packerSubnet",
+    "subnetRef": "[concat(variables('vnetID'),'/subnets/',variables('subnetName'))]",
+    "virtualNetworkName": "packerNetwork",
+    "vmStorageAccountContainerName": "images",
+    "vnetID": "[resourceId('Microsoft.Network/virtualNetworks', variables('virtualNetworkName'))]"
+>>>>>>> Support patching an ARM template.
   }
 }

builder/azure/arm/config.go

@@ -31,7 +31,9 @@ import (
 	"github.com/mitchellh/packer/packer"
 	"github.com/mitchellh/packer/template/interpolate"
 
+	"github.com/evanphx/json-patch"
 	"golang.org/x/crypto/ssh"
+	"os"
 )
 
 const (
@@ -78,6 +80,8 @@ type Config struct {
 	VirtualNetworkName              string `mapstructure:"virtual_network_name"`
 	VirtualNetworkSubnetName        string `mapstructure:"virtual_network_subnet_name"`
 	VirtualNetworkResourceGroupName string `mapstructure:"virtual_network_resource_group_name"`
+	ArmTemplatePatchFile            string `mapstructure:"arm_template_patch"`
+	armTemplatePatch                *jsonpatch.Patch
 
 	// OS
 	OSType string `mapstructure:"os_type"`
@@ -196,9 +200,13 @@ func newConfig(raws ...interface{}) (*Config, []string, error) {
 	provideDefaultValues(&c)
 	setRuntimeValues(&c)
 	setUserNamePassword(&c)
+	err = setArmTemplatePatch(&c)
+	if err != nil {
+		return nil, nil, fmt.Errorf("patch failure: %s", err)
+	}
 	err = setCloudEnvironment(&c)
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, fmt.Errorf("cloud environment: %s", err)
 	}
 
 	// NOTE: if the user did not specify a communicator, then default to both
@@ -301,6 +309,32 @@ func setUserNamePassword(c *Config) {
 	}
 }
 
+// Set the ARM template patch if there is one.  If the user did set one
+// process it completely so the code fails fast.
+func setArmTemplatePatch(c *Config) error {
+	if c.ArmTemplatePatchFile == "" {
+		return nil
+	}
+
+	fh, err := os.Open(c.ArmTemplatePatchFile)
+	if err != nil {
+		return err
+	}
+
+	bs, err := ioutil.ReadAll(fh)
+	if err != nil {
+		return err
+	}
+
+	patch, err := jsonpatch.DecodePatch(bs)
+	if err != nil {
+		return err
+	}
+
+	c.armTemplatePatch = &patch
+	return nil
+}
+
 func setCloudEnvironment(c *Config) error {
 	lookup := map[string]string{
 		"CHINA":           "AzureChinaCloud",

builder/azure/arm/config_test.go

@@ -4,6 +4,7 @@
 package arm
 
 import (
+	"io/ioutil"
 	"strings"
 	"testing"
 	"time"
@@ -533,6 +534,69 @@ func TestConfigShouldRejectMalformedCaptureContainerName(t *testing.T) {
 	}
 }
 
+// newConfig should fail if the ARM template patch is invalid.
+func TestConfigShouldValidateArmTemplatePatchIsInvalid(t *testing.T) {
+	config := map[string]string{
+		"capture_container_name": "ignore",
+		"capture_name_prefix":    "ignore",
+		"image_offer":            "ignore",
+		"image_publisher":        "ignore",
+		"image_sku":              "ignore",
+		"location":               "ignore",
+		"storage_account":        "ignore",
+		"resource_group_name":    "ignore",
+		"subscription_id":        "ignore",
+		// Does not matter for this test case, just pick one.
+		"os_type": constants.Target_Linux,
+	}
+
+	config["arm_template_patch"] = "__patch_file_does_not_exist__"
+	_, _, err := newConfig(config, getPackerConfiguration())
+	if err == nil {
+		t.Fatal("expected newConfig to fail")
+	}
+}
+
+// newConfig should succeed if the patch file is valid
+func TestConfigShouldValidateArmTemplatePatchIsJsonPatch(t *testing.T) {
+	config := map[string]string{
+		"capture_container_name": "ignore",
+		"capture_name_prefix":    "ignore",
+		"image_offer":            "ignore",
+		"image_publisher":        "ignore",
+		"image_sku":              "ignore",
+		"location":               "ignore",
+		"storage_account":        "ignore",
+		"resource_group_name":    "ignore",
+		"subscription_id":        "ignore",
+		// Does not matter for this test case, just pick one.
+		"os_type": constants.Target_Linux,
+	}
+
+	patch := `[{
+    "op": "add",
+    "path": "/resources/3/plan",
+    "value": {
+        "name": "MyName",
+        "product": "MyProduct",
+        "publisher": "MyPublisher"
+    }
+}]`
+
+	filename := "test_arm_template_patch.json"
+	ioutil.WriteFile(filename, []byte(patch), 0644)
+	config["arm_template_patch"] = filename
+
+	c, _, err := newConfig(config, getPackerConfiguration())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if c.armTemplatePatch == nil {
+		t.Fatal("expect c.armTemplatePatch to be non-nil")
+	}
+}
+
 func getArmBuilderConfiguration() map[string]string {
 	m := make(map[string]string)
 	for _, v := range requiredConfigValues {

builder/azure/arm/template_factory.go

@@ -59,9 +59,28 @@ func GetVirtualMachineDeployment(config *Config) (*resources.Deployment, error)
 	}
 
 	doc, _ := builder.ToJSON()
+	doc, err := patchArmTemplate(config, doc)
+	if err != nil {
+		return nil, err
+	}
+
 	return createDeploymentParameters(*doc, params)
 }
 
+func patchArmTemplate(config *Config, doc *string) (*string, error) {
+	if config.armTemplatePatch == nil {
+		return doc, nil
+	}
+
+	bs, err := config.armTemplatePatch.ApplyIndent([]byte(*doc), "  ")
+	if err != nil {
+		return nil, err
+	}
+
+	patched := string(bs)
+	return &patched, nil
+}
+
 func createDeploymentParameters(doc string, parameters *template.TemplateParameters) (*resources.Deployment, error) {
 	var template map[string]interface{}
 	err := json.Unmarshal(([]byte)(doc), &template)

builder/azure/arm/template_factory_test.go

@@ -2,6 +2,7 @@ package arm
 
 import (
 	"encoding/json"
+	"io/ioutil"
 	"testing"
 
 	"github.com/Azure/azure-sdk-for-go/arm/resources/resources"
@@ -177,6 +178,56 @@ func TestVirtualMachineDeployment05(t *testing.T) {
 	}
 }
 
+// Ensure that patches are applied.
+func TestVirtualMachineDeployment06(t *testing.T) {
+	config := map[string]string{
+		"capture_name_prefix":    "ignore",
+		"capture_container_name": "ignore",
+		"location":               "ignore",
+		"image_url":              "https://localhost/custom.vhd",
+		"resource_group_name":    "ignore",
+		"storage_account":        "ignore",
+		"subscription_id":        "ignore",
+		"os_type":                constants.Target_Linux,
+		"communicator":           "none",
+	}
+
+	patch := `[{
+    "op": "add",
+    "path": "/resources/3/plan",
+    "value": {
+        "name": "MySKU",
+        "product": "MyOffer",
+        "publisher": "MyPublisher"
+    }
+}]`
+
+	filename := "test_virtual_machine_deployment05.json"
+	ioutil.WriteFile(filename, []byte(patch), 0644)
+	config["arm_template_patch"] = filename
+
+	c, _, err := newConfig(config, getPackerConfiguration())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	deployment, err := GetVirtualMachineDeployment(c)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = approvaltests.VerifyJSONStruct(t, deployment.Properties.Template)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+// TODO(chrboum): create a test case for negative behavior.
+// Validate that GetVirtualMachineDeployment properly handles the case when a
+// patch fails. All of the failures that I can think of now would be caught by
+// newConfig, which is desirable because it fails faster.  Not so good, when
+// you are trying to create a failing test case.
+
 // Ensure the link values are not set, and the concrete values are set.
 func TestKeyVaultDeployment00(t *testing.T) {
 	c, _, _ := newConfig(getArmBuilderConfiguration(), getPackerConfiguration())