Fix {{packer_version}} interpolation regression (#11200)

* Add Packer version to main context at variable interpolation

Test Results Before Change
```
=== RUN   TestCoreBuild_packerVersion
    testing.go:30: err: template: root:1:2: executing "root" at <packer_version>: error calling packer_version: packer_version not available
--- FAIL: TestCoreBuild_packerVersion (0.00s)
```

Test Results After Change
```
=== RUN   TestCoreBuild_packerVersion
--- PASS: TestCoreBuild_packerVersion (0.00s)
```

* Add packer_core_version to interpolation context for HCL configs

Test Results Before Change
```
=== RUN   TestParse_build/provisioner_with_packer_version_interpolation
    common_test.go:109: Parser.getBuilds() unexpected diagnostics. testdata/build/provisioner_packer_version_interpolation.pkr.hcl:8,5-24: Failed preparing provisioner-block
 "shell" ""; render 'slice_string': template: root:1:2: executing "root" at <packer_version>: error calling packer_version: packer_version not available in:

        {{packer_version}}
--- FAIL: TestParse_build (0.01s)
```

Test Results After Change
```
--- PASS: TestParse_build (0.02s)
--- PASS: TestParse_build/provisioner_with_packer_version_interpolation (0.00s)
```

hcl2template/testdata/build/provisioner_packer_version_interpolation.pkr.hcl

@@ -0,0 +1,15 @@
+
+// starts resources to provision them.
+build {
+    sources = [
+        "source.virtualbox-iso.ubuntu-1204",
+    ]
+
+    provisioner "shell" {
+        slice_string = ["{{packer_version}}"]
+    }
+}
+
+source "virtualbox-iso" "ubuntu-1204" {
+}
+

hcl2template/types.build.post-processor.go

@@ -68,6 +68,7 @@ func (cfg *PackerConfig) startPostProcessor(source SourceUseBlock, pp *PostProce
 	}
 
 	builderVars := source.builderVariables()
+	builderVars["packer_core_version"] = cfg.CorePackerVersionString
 	builderVars["packer_debug"] = strconv.FormatBool(cfg.debug)
 	builderVars["packer_force"] = strconv.FormatBool(cfg.force)
 	builderVars["packer_on_error"] = cfg.onError

hcl2template/types.build.provisioners.go

@@ -156,6 +156,7 @@ func (cfg *PackerConfig) startProvisioner(source SourceUseBlock, pb *Provisioner
 	}
 
 	builderVars := source.builderVariables()
+	builderVars["packer_core_version"] = cfg.CorePackerVersionString
 	builderVars["packer_debug"] = strconv.FormatBool(cfg.debug)
 	builderVars["packer_force"] = strconv.FormatBool(cfg.force)
 	builderVars["packer_on_error"] = cfg.onError

hcl2template/types.build_test.go

@@ -421,6 +421,57 @@ func TestParse_build(t *testing.T) {
 			},
 			false,
 		},
+		{"provisioner with packer_version interpolation",
+			defaultParser,
+			parseTestArgs{"testdata/build/provisioner_packer_version_interpolation.pkr.hcl", nil, nil},
+			&PackerConfig{
+				CorePackerVersionString: lockedVersion,
+				Basedir:                 filepath.Join("testdata", "build"),
+				Sources: map[SourceRef]SourceBlock{
+					refVBIsoUbuntu1204: {Type: "virtualbox-iso", Name: "ubuntu-1204"},
+				},
+				Builds: Builds{
+					&BuildBlock{
+						Sources: []SourceUseBlock{
+							{
+								SourceRef: refVBIsoUbuntu1204,
+							},
+						},
+						ProvisionerBlocks: []*ProvisionerBlock{
+							{
+								PType: "shell",
+							},
+						},
+					},
+				},
+			},
+			false, false,
+			[]packersdk.Build{
+				&packer.CoreBuild{
+					Type:     "virtualbox-iso.ubuntu-1204",
+					Prepared: true,
+					Builder:  emptyMockBuilder,
+					Provisioners: []packer.CoreBuildProvisioner{
+						{
+							PType: "shell",
+							Provisioner: &HCL2Provisioner{
+								Provisioner: &MockProvisioner{
+									Config: MockConfig{
+										NestedMockConfig: NestedMockConfig{
+											Tags:        []MockTag{},
+											SliceString: []string{lockedVersion},
+										},
+										NestedSlice: []NestedMockConfig{},
+									},
+								},
+							},
+						},
+					},
+					PostProcessors: [][]packer.CoreBuildPostProcessor{},
+				},
+			},
+			false,
+		},
 	}
 	testParse(t, tests)
 }

hcl2template/types.source.go

@@ -128,6 +128,7 @@ func (cfg *PackerConfig) startBuilder(source SourceUseBlock, ectx *hcl.EvalConte
 	// prepare at a later step, to make builds from different template types
 	// easier to reason about.
 	builderVars := source.builderVariables()
+	builderVars["packer_core_version"] = cfg.CorePackerVersionString
 	builderVars["packer_debug"] = strconv.FormatBool(cfg.debug)
 	builderVars["packer_force"] = strconv.FormatBool(cfg.force)
 	builderVars["packer_on_error"] = cfg.onError

packer/core.go

@@ -21,6 +21,7 @@ import (
 	"github.com/hashicorp/packer-plugin-sdk/template/interpolate"
 	packerregistry "github.com/hashicorp/packer/internal/packer_registry"
 	"github.com/hashicorp/packer/internal/packer_registry/env"
+	packerversion "github.com/hashicorp/packer/version"
 )
 
 // Core is the main executor of Packer. If Packer is being used as a
@@ -453,8 +454,9 @@ func (c *Core) Build(n string) (packersdk.Build, error) {
 // Context returns an interpolation context.
 func (c *Core) Context() *interpolate.Context {
 	return &interpolate.Context{
-		TemplatePath:  c.Template.Path,
-		UserVariables: c.variables,
+		TemplatePath:            c.Template.Path,
+		UserVariables:           c.variables,
+		CorePackerVersionString: packerversion.FormattedVersion(),
 	}
 }
 

packer/core_test.go

@@ -11,6 +11,7 @@ import (
 	packersdk "github.com/hashicorp/packer-plugin-sdk/packer"
 	"github.com/hashicorp/packer-plugin-sdk/template"
 	configHelper "github.com/hashicorp/packer-plugin-sdk/template/config"
+	"github.com/hashicorp/packer/version"
 )
 
 func TestCoreBuildNames(t *testing.T) {
@@ -845,3 +846,30 @@ func TestCoreBuild_provRetry(t *testing.T) {
 		t.Fatal("provisioner should retry for max_retries integer value")
 	}
 }
+
+func TestCoreBuild_packerVersion(t *testing.T) {
+	config := TestCoreConfig(t)
+	testCoreTemplate(t, config, fixtureDir("build-var-packer-version.json"))
+	b := TestBuilder(t, config, "test")
+	core := TestCore(t, config)
+
+	expected := version.FormattedVersion()
+	build, err := core.Build("test")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if _, err := build.Prepare(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	// Interpolate the config
+	var result map[string]interface{}
+	err = configHelper.Decode(&result, nil, b.PrepareConfig...)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if result["value"] != expected {
+		t.Fatalf("bad: %#v", result)
+	}
+}

packer/test-fixtures/build-var-packer-version.json

@@ -0,0 +1,9 @@
+{
+  "variables": {
+    "CreatedBy": "{{packer_version}}"
+  },
+    "builders": [{
+        "type": "test",
+        "value": "{{user `CreatedBy`}}"
+    }]
+}