Allow skipping parsing of locals

Since `locals` can have side effects, we might run into cases when
we don't need to pasre them. One example is `checkVersionConstraints()`,
which is executed early on and relies on parsing Terraform.

Closes: gruntwork-io#1427

cli/cli_app.go

@@ -460,6 +460,7 @@ func checkVersionConstraints(terragruntOptions *options.TerragruntOptions) error
 		terragruntOptions,
 		nil,
 		[]config.PartialDecodeSectionType{config.TerragruntVersionConstraints},
+		false,
 	)
 	if err != nil {
 		return err

config/config.go

@@ -408,7 +408,7 @@ func ParseConfigString(configString string, terragruntOptions *options.Terragrun
 	}
 
 	// Decode just the Base blocks. See the function docs for DecodeBaseBlocks for more info on what base blocks are.
-	localsAsCty, terragruntInclude, includeForDecode, err := DecodeBaseBlocks(terragruntOptions, parser, file, filename, includeFromChild)
+	localsAsCty, terragruntInclude, includeForDecode, err := DecodeBaseBlocks(terragruntOptions, parser, file, filename, includeFromChild, true)
 	if err != nil {
 		return nil, err
 	}

config/config_partial.go

@@ -98,6 +98,7 @@ func DecodeBaseBlocks(
 	hclFile *hcl.File,
 	filename string,
 	includeFromChild *IncludeConfig,
+	parseLocals bool,
 ) (*cty.Value, *terragruntInclude, *IncludeConfig, error) {
 	// Decode just the `include` block, and verify that it's allowed here
 	terragruntInclude, err := decodeAsTerragruntInclude(
@@ -116,13 +117,18 @@ func DecodeBaseBlocks(
 
 	// Evaluate all the expressions in the locals block separately and generate the variables list to use in the
 	// evaluation context.
-	locals, err := evaluateLocalsBlock(terragruntOptions, parser, hclFile, filename, includeForDecode)
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	localsAsCty, err := convertValuesMapToCtyVal(locals)
-	if err != nil {
-		return nil, nil, nil, err
+	var localsAsCty cty.Value
+	if parseLocals {
+		locals, err := evaluateLocalsBlock(terragruntOptions, parser, hclFile, filename, includeForDecode)
+		if err != nil {
+			return nil, nil, nil, err
+		}
+		localsAsCty, err = convertValuesMapToCtyVal(locals)
+		if err != nil {
+			return nil, nil, nil, err
+		}
+	} else {
+		localsAsCty = cty.Value{}
 	}
 
 	return &localsAsCty, terragruntInclude, includeForDecode, nil
@@ -133,13 +139,14 @@ func PartialParseConfigFile(
 	terragruntOptions *options.TerragruntOptions,
 	include *IncludeConfig,
 	decodeList []PartialDecodeSectionType,
+	parseLocals bool,
 ) (*TerragruntConfig, error) {
 	configString, err := util.ReadFileAsString(filename)
 	if err != nil {
 		return nil, err
 	}
 
-	config, err := PartialParseConfigString(configString, terragruntOptions, include, filename, decodeList)
+	config, err := PartialParseConfigString(configString, terragruntOptions, include, filename, decodeList, parseLocals)
 	if err != nil {
 		return nil, err
 	}
@@ -168,6 +175,7 @@ func PartialParseConfigString(
 	includeFromChild *IncludeConfig,
 	filename string,
 	decodeList []PartialDecodeSectionType,
+	parseLocals bool,
 ) (*TerragruntConfig, error) {
 	// Parse the HCL string into an AST body that can be decoded multiple times later without having to re-parse
 	parser := hclparse.NewParser()
@@ -177,7 +185,7 @@ func PartialParseConfigString(
 	}
 
 	// Decode just the Base blocks. See the function docs for DecodeBaseBlocks for more info on what base blocks are.
-	localsAsCty, terragruntInclude, includeForDecode, err := DecodeBaseBlocks(terragruntOptions, parser, file, filename, includeFromChild)
+	localsAsCty, terragruntInclude, includeForDecode, err := DecodeBaseBlocks(terragruntOptions, parser, file, filename, includeFromChild, parseLocals)
 	if err != nil {
 		return nil, err
 	}
@@ -321,6 +329,7 @@ func partialParseIncludedConfig(includedConfig *IncludeConfig, terragruntOptions
 		terragruntOptions,
 		includedConfig,
 		decodeList,
+		true,
 	)
 }
 

config/config_partial_test.go

@@ -20,7 +20,7 @@ dependencies {
 }
 `
 
-	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock})
+	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 
@@ -48,10 +48,10 @@ dependencies {
 prevent_destroy = false
 `
 
-	_, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{TerragruntFlags})
+	_, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{TerragruntFlags}, true)
 	assert.NoError(t, err)
 
-	_, err = PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock})
+	_, err = PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock}, true)
 	assert.Error(t, err)
 }
 
@@ -67,7 +67,7 @@ prevent_destroy = true
 skip = true
 `
 
-	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock, TerragruntFlags})
+	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock, TerragruntFlags}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 
@@ -87,7 +87,7 @@ skip = true
 func TestPartialParseOmittedItems(t *testing.T) {
 	t.Parallel()
 
-	terragruntConfig, err := PartialParseConfigString("", mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock, TerragruntFlags})
+	terragruntConfig, err := PartialParseConfigString("", mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock, TerragruntFlags}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 	assert.Nil(t, terragruntConfig.Dependencies)
@@ -103,18 +103,18 @@ func TestPartialParseDoesNotResolveIgnoredBlockEvenInParent(t *testing.T) {
 	t.Parallel()
 
 	opts := mockOptionsForTestWithConfigPath(t, "../test/fixture-partial-parse/ignore-bad-block-in-parent/child/"+DefaultTerragruntConfigPath)
-	_, err := PartialParseConfigFile(opts.TerragruntConfigPath, opts, nil, []PartialDecodeSectionType{TerragruntFlags})
+	_, err := PartialParseConfigFile(opts.TerragruntConfigPath, opts, nil, []PartialDecodeSectionType{TerragruntFlags}, true)
 	assert.NoError(t, err)
 
-	_, err = PartialParseConfigFile(opts.TerragruntConfigPath, opts, nil, []PartialDecodeSectionType{DependenciesBlock})
+	_, err = PartialParseConfigFile(opts.TerragruntConfigPath, opts, nil, []PartialDecodeSectionType{DependenciesBlock}, true)
 	assert.Error(t, err)
 }
 
 func TestPartialParseOnlyInheritsSelectedBlocksFlags(t *testing.T) {
 	t.Parallel()
 
 	opts := mockOptionsForTestWithConfigPath(t, "../test/fixture-partial-parse/partial-inheritance/child/"+DefaultTerragruntConfigPath)
-	terragruntConfig, err := PartialParseConfigFile(opts.TerragruntConfigPath, opts, nil, []PartialDecodeSectionType{TerragruntFlags})
+	terragruntConfig, err := PartialParseConfigFile(opts.TerragruntConfigPath, opts, nil, []PartialDecodeSectionType{TerragruntFlags}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 	assert.Nil(t, terragruntConfig.Dependencies)
@@ -130,7 +130,7 @@ func TestPartialParseOnlyInheritsSelectedBlocksDependencies(t *testing.T) {
 	t.Parallel()
 
 	opts := mockOptionsForTestWithConfigPath(t, "../test/fixture-partial-parse/partial-inheritance/child/"+DefaultTerragruntConfigPath)
-	terragruntConfig, err := PartialParseConfigFile(opts.TerragruntConfigPath, opts, nil, []PartialDecodeSectionType{DependenciesBlock})
+	terragruntConfig, err := PartialParseConfigFile(opts.TerragruntConfigPath, opts, nil, []PartialDecodeSectionType{DependenciesBlock}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 
@@ -155,7 +155,7 @@ dependency "vpc" {
 }
 `
 
-	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock})
+	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 
@@ -178,7 +178,7 @@ dependency "sql" {
 }
 `
 
-	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock})
+	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 
@@ -203,7 +203,7 @@ dependency "sql" {
 }
 `
 
-	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock})
+	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 
@@ -229,7 +229,7 @@ dependency "sql" {
 }
 `
 
-	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock, DependencyBlock})
+	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependenciesBlock, DependencyBlock}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 
@@ -255,7 +255,7 @@ dependency "sql" {
 }
 `
 
-	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock, DependenciesBlock})
+	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock, DependenciesBlock}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 
@@ -281,7 +281,7 @@ dependency "sql" {
 }
 `
 
-	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock, DependenciesBlock})
+	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{DependencyBlock, DependenciesBlock}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 
@@ -307,7 +307,7 @@ terraform {
 }
 `
 
-	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{TerraformSource})
+	terragruntConfig, err := PartialParseConfigString(config, mockOptionsForTest(t), nil, DefaultTerragruntConfigPath, []PartialDecodeSectionType{TerraformSource}, true)
 	require.NoError(t, err)
 	assert.True(t, terragruntConfig.IsPartial)
 

config/dependency.go

@@ -162,7 +162,7 @@ func getDependencyBlockConfigPathsByFilepath(configPath string, terragruntOption
 	// TerragruntConfig.Dependencies. Note that since we aren't passing in `DependenciesBlock` to the
 	// PartialDecodeSectionType list, the Dependencies attribute will not include any dependencies specified via the
 	// dependencies block.
-	tgConfig, err := PartialParseConfigFile(configPath, terragruntOptions, nil, []PartialDecodeSectionType{DependencyBlock})
+	tgConfig, err := PartialParseConfigFile(configPath, terragruntOptions, nil, []PartialDecodeSectionType{DependencyBlock}, true)
 	if err != nil {
 		return nil, err
 	}
@@ -368,6 +368,7 @@ func cloneTerragruntOptionsForDependencyOutput(terragruntOptions *options.Terrag
 			targetOptions,
 			nil,
 			[]PartialDecodeSectionType{TerraformBlock},
+			true,
 		)
 		if err != nil {
 			return nil, err
@@ -402,10 +403,10 @@ func getTerragruntOutputJson(terragruntOptions *options.TerragruntOptions, targe
 		return nil, err
 	}
 
-	// First attempt to parse the `remote_state` blocks without parsing/getting dependency outputs. If this is possible,
-	// proceed to routine that fetches remote state directly. Otherwise, fallback to calling `terragrunt output`
-	// directly.
-	remoteStateTGConfig, err := PartialParseConfigFile(targetConfig, targetTGOptions, nil, []PartialDecodeSectionType{RemoteStateBlock, TerragruntFlags})
+	// First, attempt to parse the `remote_state` blocks without parsing/getting dependency outputs. If this is
+	// possible, proceed to routine that fetches remote state directly. Otherwise, fallback to calling
+	// `terragrunt output` directly.
+	remoteStateTGConfig, err := PartialParseConfigFile(targetConfig, targetTGOptions, nil, []PartialDecodeSectionType{RemoteStateBlock, TerragruntFlags}, true)
 	if err != nil || !canGetRemoteState(remoteStateTGConfig.RemoteState) {
 		terragruntOptions.Logger.Warningf("Could not parse remote_state block from target config %s", targetConfig)
 		terragruntOptions.Logger.Warningf("Falling back to terragrunt output.")
@@ -435,7 +436,7 @@ func canGetRemoteState(remoteState *remote.RemoteState) bool {
 func terragruntAlreadyInit(terragruntOptions *options.TerragruntOptions, configPath string) (bool, string, error) {
 	// We need to first determine the working directory where the terraform source should be located. This is dependent
 	// on the source field of the terraform block in the config.
-	terraformBlockTGConfig, err := PartialParseConfigFile(configPath, terragruntOptions, nil, []PartialDecodeSectionType{TerraformSource})
+	terraformBlockTGConfig, err := PartialParseConfigFile(configPath, terragruntOptions, nil, []PartialDecodeSectionType{TerraformSource}, true)
 	if err != nil {
 		return false, "", err
 	}

configstack/module.go

@@ -253,6 +253,7 @@ func resolveTerraformModule(terragruntConfigPath string, terragruntOptions *opti
 			config.DependenciesBlock,
 			config.DependencyBlock,
 		},
+		true,
 	)
 	if err != nil {
 		return nil, errors.WithStackTrace(ErrorProcessingModule{UnderlyingError: err, HowThisModuleWasFound: howThisModuleWasFound, ModulePath: terragruntConfigPath})