adding function to extract terraform vars from var file

go.mod

@@ -22,6 +22,7 @@ require (
 	github.com/google/uuid v1.1.1
 	github.com/gruntwork-io/gruntwork-cli v0.7.0
 	github.com/hashicorp/go-multierror v1.1.0
+	github.com/hashicorp/hcl v1.0.0
 	github.com/imdario/mergo v0.3.7 // indirect
 	github.com/jinzhu/copier v0.0.0-20190924061706-b57f9002281a
 	github.com/jstemmer/go-junit-report v0.9.1

go.sum

@@ -250,6 +250,7 @@ github.com/hashicorp/go-multierror v1.1.0/go.mod h1:spPvp8C1qA32ftKqdAHm4hHTbPw+
 github.com/hashicorp/golang-lru v0.5.0/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
 github.com/hashicorp/golang-lru v0.5.1/go.mod h1:/m3WP610KZHVQ1SGc6re/UDhFvYD7pJ4Ao+sR/qLZy8=
 github.com/hashicorp/golang-lru v0.5.3/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
+github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
 github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=

modules/terraform/errors.go

@@ -56,3 +56,32 @@ type UnexpectedOutputType struct {
 func (err UnexpectedOutputType) Error() string {
 	return fmt.Sprintf("Expected output '%s' to be of type '%s' but got '%s'", err.Key, err.ExpectedType, err.ActualType)
 }
+
+// VarFileNotFound is an error that occurs when a var file cannot be found in an option's VarFile list
+type VarFileNotFound struct {
+	Path string
+}
+
+func (err VarFileNotFound) Error() string {
+	return fmt.Sprintf("Var file '%s' not found", err.Path)
+}
+
+// InputFileKeyNotFound occurs when tfvar file does not contain a value for the key
+// specified in the function call
+type InputFileKeyNotFound struct {
+	FilePath string
+	Key      string
+}
+
+func (err InputFileKeyNotFound) Error() string {
+	return fmt.Sprintf("tfvar file %q doesn't contain a value for the key %q", err.FilePath, err.Key)
+}
+
+type HclDecodeError struct {
+	FilePath  string
+	ErrorText string
+}
+
+func (err HclDecodeError) Error() string {
+	return fmt.Sprintf("%s - %s", err.FilePath, err.ErrorText)
+}

modules/terraform/var-file.go

@@ -0,0 +1,149 @@
+package terraform
+
+import (
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"reflect"
+	"testing"
+
+	"github.com/hashicorp/hcl"
+	"github.com/stretchr/testify/require"
+)
+
+// GetVariableAsStringFromVarFile Gets the string represention of a variable from a provided input file found in VarFile
+// For list or map, use GetVariableAsListFromVarFile or GetVariableAsMapFromVarFile, respectively.
+func GetVariableAsStringFromVarFile(t *testing.T, fileName string, key string) string {
+	result, err := GetVariableAsStringFromVarFileE(t, fileName, key)
+	require.NoError(t, err)
+
+	return result
+}
+
+// GetVariableAsStringFromVarFileE Gets the string represention of a variable from a provided input file found in VarFile
+// Will return an error if GetAllVariablesFromVarFileE returns an error or the key provided does not exist in the file.
+// For list or map, use GetVariableAsListFromVarFile or GetVariableAsMapFromVarFile, respectively.
+func GetVariableAsStringFromVarFileE(t *testing.T, fileName string, key string) (string, error) {
+	var variables map[string]interface{}
+
+	err := GetAllVariablesFromVarFileE(t, fileName, &variables)
+
+	if err != nil {
+		return "", err
+	}
+
+	variable, exists := variables[key]
+
+	if !exists {
+		return "", InputFileKeyNotFound{FilePath: fileName, Key: key}
+	}
+
+	return fmt.Sprintf("%v", variable), nil
+}
+
+// GetVariableAsMapFromVarFile Gets the map represention of a variable from a provided input file found in VarFile
+// Note that this returns a map of strings. For maps containing complex types, use GetAllVariablesFromVarFile.
+func GetVariableAsMapFromVarFile(t *testing.T, fileName string, key string) map[string]string {
+	result, err := GetVariableAsMapFromVarFileE(t, fileName, key)
+	require.NoError(t, err)
+
+	return result
+}
+
+// GetVariableAsMapFromVarFileE Gets the map represention of a variable from a provided input file found in VarFile.
+// Note that this returns a map of strings. For maps containing complex types, use GetAllVariablesFromVarFile
+// Returns an error if GetAllVariablesFromVarFileE returns an error, the key provided does not exist, or the value associated with the key is not a map
+func GetVariableAsMapFromVarFileE(t *testing.T, fileName string, key string) (map[string]string, error) {
+	var variables map[string]interface{}
+
+	resultMap := make(map[string]string)
+	err := GetAllVariablesFromVarFileE(t, fileName, &variables)
+
+	if err != nil {
+		return nil, err
+	}
+
+	variable, exists := variables[key]
+
+	if !exists {
+		return nil, InputFileKeyNotFound{FilePath: fileName, Key: key}
+	}
+
+	if reflect.TypeOf(variable).String() != "[]map[string]interface {}" {
+		return nil, UnexpectedOutputType{Key: key, ExpectedType: "[]map[string]interface {}", ActualType: reflect.TypeOf(variable).String()}
+	}
+
+	mapKeys := variable.([]map[string]interface{})
+
+	if len(mapKeys) == 0 {
+		return nil, errors.New("no map keys could be found for given map")
+	}
+
+	for mapKey, mapVal := range mapKeys[0] {
+		resultMap[mapKey] = fmt.Sprintf("%v", mapVal)
+	}
+
+	return resultMap, nil
+}
+
+// GetVariableAsListFromVarFile Gets the string list represention of a variable from a provided input file found in VarFile
+// Note that this returns a list of strings. For lists containing complex types, use GetAllVariablesFromVarFile.
+func GetVariableAsListFromVarFile(t *testing.T, fileName string, key string) []string {
+	result, err := GetVariableAsListFromVarFileE(t, fileName, key)
+	require.NoError(t, err)
+
+	return result
+}
+
+// GetVariableAsListFromVarFileE Gets the string list represention of a variable from a provided input file found in VarFile
+// Note that this returns a list of strings. For lists containing complex types, use GetAllVariablesFromVarFile.
+// Will return error if GetAllVariablesFromVarFileE returns an error, the key provided does not exist, or the value associated with the key is not a list
+func GetVariableAsListFromVarFileE(t *testing.T, fileName string, key string) ([]string, error) {
+	var variables map[string]interface{}
+	resultArray := []string{}
+	err := GetAllVariablesFromVarFileE(t, fileName, &variables)
+
+	if err != nil {
+		return nil, err
+	}
+
+	variable, exists := variables[key]
+
+	if !exists {
+		return nil, InputFileKeyNotFound{FilePath: fileName, Key: key}
+	}
+
+	if reflect.TypeOf(variable).String() != "[]interface {}" {
+		return nil, UnexpectedOutputType{Key: key, ExpectedType: "[]interface {}", ActualType: reflect.TypeOf(variable).String()}
+	}
+
+	for _, item := range variable.([]interface{}) {
+		resultArray = append(resultArray, fmt.Sprintf("%v", item))
+	}
+
+	return resultArray, nil
+}
+
+// GetAllVariablesFromVarFile Parses all data from a provided input file found in VarFile and stores the result in the value pointed to by out
+func GetAllVariablesFromVarFile(t *testing.T, fileName string, out interface{}) {
+	err := GetAllVariablesFromVarFileE(t, fileName, out)
+	require.NoError(t, err)
+}
+
+// GetAllVariablesFromVarFileE Parses all data from a provided input file found ind in VarFile and stores the result in the value pointed to by out
+// Returns an error if the specified file does not exist, the specified file is not readable, or the specified file cannot be decoded from HCL
+func GetAllVariablesFromVarFileE(t *testing.T, fileName string, out interface{}) error {
+	fileContents, err := ioutil.ReadFile(fileName)
+
+	if err != nil {
+		return err
+	}
+
+	err = hcl.Decode(out, string(fileContents))
+
+	if err != nil {
+		return HclDecodeError{FilePath: fileName, ErrorText: err.Error()}
+	}
+
+	return nil
+}