Implement merge of config and credentials file

Loading the profile data from the config and credentials files
will new merge the data of the two files. The data in the second
file is preferred. This means in the current load order that the
credentials file will overwrite configuration in the config
file.

Test data and test was added for this case.

config/config_test.go

@@ -4,15 +4,15 @@ import (
 	"testing"
 	"time"
 
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
+	assertmod "github.com/stretchr/testify/assert"
+	requiremod "github.com/stretchr/testify/require"
 )
 
 func TestConfigInitLoad(t *testing.T) {
 
 	var (
-		assert  = assert.New(t)
-		require = require.New(t)
+		assert  = assertmod.New(t)
+		require = requiremod.New(t)
 	)
 
 	split := &Config{
@@ -55,14 +55,13 @@ func TestConfigInitLoad(t *testing.T) {
 		assert.Equal("arn:aws:iam::123456789012:role/marketingadmin", profile.RoleARN)
 		assert.Equal(profile.AccessKeyID, profile.Value().AccessKeyID)
 		assert.Equal(profile.SecretAccessKey, profile.Value().SecretAccessKey)
-
 	}
 
 }
 
 func TestConfigInitValidate(t *testing.T) {
 
-	var assert = assert.New(t)
+	var assert = assertmod.New(t)
 
 	valid := &Config{
 		Duration: 5 * time.Minute,
@@ -79,3 +78,30 @@ func TestConfigInitValidate(t *testing.T) {
 	assert.Errorf(invalid.Init(), "invalid grace (f) for duration (d)")
 
 }
+
+func TestMergeConfigAndCredentials(t *testing.T) {
+
+	var (
+		assert  = assertmod.New(t)
+		require = requiremod.New(t)
+	)
+
+	config := &Config{
+		ConfigFile:            "testdata/config",
+		Duration:              5 * time.Minute,
+		Grace:                 1 * time.Minute,
+		SharedCredentialsFile: "testdata/credentials",
+	}
+
+	err := config.Init()
+	require.NoError(err)
+
+	mfaProfile, ok := config.Profiles["test-mfa"]
+	require.True(ok)
+
+	assert.Equal("test-mfa", mfaProfile.Name)
+
+	assert.Equal("arn:aws:iam::123456789012:mfa/jondoe", mfaProfile.MFASerial)
+	assert.Equal("AKIAIOSFODNN7EXAMPLE", mfaProfile.Value().AccessKeyID)
+	assert.Equal("wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY", mfaProfile.Value().SecretAccessKey)
+}

config/profile.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"github.com/aws/aws-sdk-go/aws/credentials"
+	"reflect"
 )
 
 // Profile is a long- or short-time credential profile managed in a shared config
@@ -30,3 +31,15 @@ func (p *Profile) Value() credentials.Value {
 	}
 
 }
+
+func (p *Profile) Merge(profileToMerge *Profile) {
+	val1 := reflect.ValueOf(p).Elem()
+	val2 := reflect.ValueOf(profileToMerge).Elem()
+
+	for i := 0; i < val1.NumField(); i++ {
+		newFieldValue := val2.Field(i)
+		if !newFieldValue.IsZero() {
+			val1.Field(i).Set(newFieldValue)
+		}
+	}
+}

config/profiles.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"io/ioutil"
+	"strings"
 
 	"github.com/pkg/errors"
 	ini "gopkg.in/ini.v1"
@@ -50,6 +51,7 @@ func Load(files ...string) (Profiles, error) {
 		for _, section := range f.Sections() {
 
 			name := section.Name()
+			name = strings.TrimPrefix(name, "profile ")
 
 			if name == "preview" {
 				continue
@@ -64,12 +66,12 @@ func Load(files ...string) (Profiles, error) {
 				goto init
 			}
 
-			if err := section.MapTo(profile); err != nil {
+			sectionProfile := new(Profile)
+			if err := section.MapTo(sectionProfile); err != nil {
 				return nil, err
 			}
-
-			profile.Name = name
-
+			sectionProfile.Name = name
+			profile.Merge(sectionProfile)
 		}
 
 	}

config/testdata/config

@@ -1,3 +1,8 @@
 [default]
 region=us-west-2
 output=json
+
+[profile test-mfa]
+region=us-west-2
+output=json
+mfa_serial=arn:aws:iam::123456789012:mfa/jondoe

config/testdata/credentials

@@ -7,3 +7,7 @@ role_arn=arn:aws:iam::123456789012:role/marketingadmin
 source_profile=default
 external_id=123456
 mfa_serial=arn:aws:iam::123456789012:mfa/jonsmith
+
+[test-mfa]
+aws_access_key_id=AKIAIOSFODNN7EXAMPLE
+aws_secret_access_key=wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY