core: Decode: when in HCL2 decoding mode; reset the whole struct before preparing it. (#9622)

* core: Decode when in HCL2 decoding mode; reset the whole struct before preparing it.
* HCL2: add path variables + docs & tests

Co-authored-by: Megan Marsh <megan@hashicorp.com>

command/build_test.go

@@ -7,6 +7,8 @@ import (
 	"math"
 	"os"
 	"path/filepath"
+	"runtime"
+	"strings"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -323,6 +325,44 @@ func TestBuild(t *testing.T) {
 	}
 }
 
+func Test_build_output(t *testing.T) {
+
+	tc := []struct {
+		command  []string
+		env      []string
+		expected string
+		runtime  string
+	}{
+		{[]string{"build", "--color=false", testFixture("hcl", "reprepare", "shell-local.pkr.hcl")}, nil,
+			`
+    null.example: hello from the NULL builder packeruser
+Build 'null.example' finished.
+`, "posix"},
+		{[]string{"build", "--color=false", testFixture("hcl", "reprepare", "shell-local-windows.pkr.hcl")}, nil,
+			`
+    null.example: hello from the NULL  builder packeruser
+Build 'null.example' finished.
+`, "windows"},
+	}
+
+	for _, tc := range tc {
+		if (runtime.GOOS == "windows") != (tc.runtime == "windows") {
+			continue
+		}
+		t.Run(fmt.Sprintf("packer %s", tc.command), func(t *testing.T) {
+			p := helperCommand(t, tc.command...)
+			p.Env = append(p.Env, tc.env...)
+			bs, err := p.Output()
+			if err != nil {
+				t.Fatalf("%v: %s", err, bs)
+			}
+			if !strings.Contains(string(bs), tc.expected) {
+				t.Fatalf("Should have given output %s.\nReceived: %s", tc.expected, string(bs))
+			}
+		})
+	}
+}
+
 func TestBuildOnlyFileCommaFlags(t *testing.T) {
 	c := &BuildCommand{
 		Meta: testMetaFile(t),

command/console_test.go

@@ -2,6 +2,7 @@ package command
 
 import (
 	"fmt"
+	"os"
 	"path/filepath"
 	"strings"
 	"testing"
@@ -12,6 +13,10 @@ import (
 )
 
 func Test_console(t *testing.T) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("Getwd: %v", err)
+	}
 
 	tc := []struct {
 		piped    string
@@ -25,6 +30,8 @@ func Test_console(t *testing.T) {
 		{"upper(var.fruit)", []string{"console", filepath.Join(testFixture("var-arg"), "fruit_builder.pkr.hcl")}, []string{"PKR_VAR_fruit=potato"}, "POTATO\n"},
 		{"1 + 5", []string{"console", "--config-type=hcl2"}, nil, "6\n"},
 		{"var.images", []string{"console", filepath.Join(testFixture("var-arg"), "map.pkr.hcl")}, nil, "{\n" + `  "key" = "value"` + "\n}\n"},
+		{"path.cwd", []string{"console", filepath.Join(testFixture("var-arg"), "map.pkr.hcl")}, nil, strings.ReplaceAll(cwd, `\`, `/`) + "\n"},
+		{"path.root", []string{"console", filepath.Join(testFixture("var-arg"), "map.pkr.hcl")}, nil, strings.ReplaceAll(testFixture("var-arg"), `\`, `/`) + "\n"},
 	}
 
 	for _, tc := range tc {

command/exec_test.go

@@ -87,6 +87,8 @@ func TestHelperProcess(*testing.T) {
 		os.Exit((&ConsoleCommand{Meta: commandMeta()}).Run(args))
 	case "inspect":
 		os.Exit((&InspectCommand{Meta: commandMeta()}).Run(args))
+	case "build":
+		os.Exit((&BuildCommand{Meta: commandMeta()}).Run(args))
 	default:
 		fmt.Fprintf(os.Stderr, "Unknown command %q\n", cmd)
 		os.Exit(2)

command/test-fixtures/hcl/reprepare/hello.sh

@@ -0,0 +1 @@
+echo hello from the ${BUILDER} builder ${USER}

command/test-fixtures/hcl/reprepare/shell-local-windows.pkr.hcl

@@ -0,0 +1,13 @@
+source "null" "example" {
+    communicator = "none"
+}
+
+build {
+	sources = [
+		"source.null.example"
+	]
+	provisioner "shell-local" {
+		script = "./${path.root}/test_cmd.cmd"
+		environment_vars = ["USER=packeruser", "BUILDER=${upper(build.ID)}"]
+	}
+}

command/test-fixtures/hcl/reprepare/shell-local.pkr.hcl

@@ -0,0 +1,13 @@
+source "null" "example" {
+    communicator = "none"
+}
+
+build {
+	sources = [
+		"source.null.example"
+	]
+	provisioner "shell-local" {
+		script = "./${path.root}/hello.sh"
+		environment_vars = ["USER=packeruser", "BUILDER=${upper(build.ID)}"]
+	}
+}

command/test-fixtures/hcl/reprepare/test_cmd.cmd

@@ -0,0 +1 @@
+echo hello from the %BUILDER% builder %USER%

common/shell-local/run.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"path/filepath"
 	"runtime"
 	"sort"
 	"strings"
@@ -70,7 +71,17 @@ func Run(ctx context.Context, ui packer.Ui, config *Config, generatedData map[st
 	}
 
 	for _, script := range scripts {
-		interpolatedCmds, err := createInterpolatedCommands(config, script, flattenedEnvVars)
+		// use absolute path in case the script is linked with forward slashes
+		// on windows.
+		absScript, err := filepath.Abs(script)
+		if err != nil {
+			return false, fmt.Errorf(
+				"Error executing script: %s\n%v\n",
+				absScript,
+				err,
+			)
+		}
+		interpolatedCmds, err := createInterpolatedCommands(config, absScript, flattenedEnvVars)
 		if err != nil {
 			return false, err
 		}
@@ -91,7 +102,7 @@ func Run(ctx context.Context, ui packer.Ui, config *Config, generatedData map[st
 			return false, fmt.Errorf(
 				"Error executing script: %s\n\n"+
 					"Please see output above for more information.",
-				script)
+				absScript)
 		}
 
 		if err := config.ValidExitCode(cmd.ExitStatus()); err != nil {

hcl2template/common_test.go

@@ -77,6 +77,9 @@ func testParse(t *testing.T, tests []parseTest) {
 					ProvisionerBlock{},
 					PostProcessorBlock{},
 				),
+				cmpopts.IgnoreFields(PackerConfig{},
+					"Cwd", // Cwd will change for every computer
+				),
 				cmpopts.IgnoreTypes(HCL2Ref{}),
 				cmpopts.IgnoreTypes([]hcl.Range{}),
 				cmpopts.IgnoreTypes(hcl.Range{}),

hcl2template/parser.go

@@ -70,7 +70,7 @@ func (p *Parser) Parse(filename string, varFiles []string, argVars map[string]st
 		hclFiles, jsonFiles, moreDiags := GetHCL2Files(filename, hcl2FileExt, hcl2JsonFileExt)
 		diags = append(diags, moreDiags...)
 		if len(hclFiles)+len(jsonFiles) == 0 {
-			diags = append(moreDiags, &hcl.Diagnostic{
+			diags = append(diags, &hcl.Diagnostic{
 				Severity: hcl.DiagError,
 				Summary:  "Could not find any config file in " + filename,
 				Detail: "A config file must be suffixed with `.pkr.hcl` or " +
@@ -96,8 +96,17 @@ func (p *Parser) Parse(filename string, varFiles []string, argVars map[string]st
 	if isDir, err := isDir(basedir); err == nil && !isDir {
 		basedir = filepath.Dir(basedir)
 	}
+	wd, err := os.Getwd()
+	if err != nil {
+		diags = append(diags, &hcl.Diagnostic{
+			Severity: hcl.DiagError,
+			Summary:  "Could not find current working directory",
+			Detail:   err.Error(),
+		})
+	}
 	cfg := &PackerConfig{
 		Basedir:               basedir,
+		Cwd:                   wd,
 		builderSchemas:        p.BuilderSchemas,
 		provisionersSchemas:   p.ProvisionersSchemas,
 		postProcessorsSchemas: p.PostProcessorsSchemas,

hcl2template/types.packer_config.go

@@ -16,6 +16,8 @@ import (
 type PackerConfig struct {
 	// Directory where the config files are defined
 	Basedir string
+	// directory Packer was called from
+	Cwd string
 
 	// Available Source blocks
 	Sources map[SourceRef]SourceBlock
@@ -49,6 +51,7 @@ type ValidationOptions struct {
 const (
 	inputVariablesAccessor = "var"
 	localsAccessor         = "local"
+	pathVariablesAccessor  = "path"
 	sourcesAccessor        = "source"
 	buildAccessor          = "build"
 )
@@ -69,6 +72,10 @@ func (cfg *PackerConfig) EvalContext(variables map[string]cty.Value) *hcl.EvalCo
 				"name": cty.UnknownVal(cty.String),
 			}),
 			buildAccessor: cty.UnknownVal(cty.EmptyObject),
+			pathVariablesAccessor: cty.ObjectVal(map[string]cty.Value{
+				"cwd":  cty.StringVal(strings.ReplaceAll(cfg.Cwd, `\`, `/`)),
+				"root": cty.StringVal(strings.ReplaceAll(cfg.Basedir, `\`, `/`)),
+			}),
 		},
 	}
 	for k, v := range variables {

helper/config/decode.go

@@ -72,6 +72,18 @@ func Decode(target interface{}, config *DecodeOpts, raws ...interface{}) error {
 			return err
 		}
 		raws[i] = raw
+		{
+			// reset target to zero.
+			// In HCL2, we need to prepare provisioners/post-processors after a
+			// builder has started in order to have build values correctly
+			// extrapolated. Packer plugins have never been prepared twice in
+			// the past and some of them set fields during their Validation
+			// steps; which end up in an invalid provisioner/post-processor,
+			// like in [GH-9596]. This ensures Packer plugin will be reset
+			// right before we Prepare them.
+			p := reflect.ValueOf(target).Elem()
+			p.Set(reflect.Zero(p.Type()))
+		}
 	}
 	if config == nil {
 		config = &DecodeOpts{Interpolate: true}

website/data/docs-navigation.js

@@ -144,6 +144,7 @@ export default [
       'variables',
       'locals',
       'contextual-variables',
+      'path-variables',
       'syntax',
       'onlyexcept',
       'expressions',

website/pages/docs/from-1.5/path-variables.mdx

@@ -0,0 +1,14 @@
+---
+layout: docs
+page_title: Path Variables - HCL Configuration Language
+sidebar_title: Path Variables
+description: |-
+  Special variables provide directory information. This page covers all path
+  variables.
+---
+
+# Path variables
+
+- `path.cwd`: the directory from where Packer was started.
+
+- `path.root`: the directory of the input HCL file or the input folder.