internal/ini: Normalize Section keys to lowercase (#495)

Updates the SDK's ini utility to read all keys as case-insensitive, and store them as lowercase for lookup.

This is to match the behavior of the parsing in Python, and the boto based AWS CLI, where the keys are normalized to lowercase.

Author: gaqzi

CHANGELOG_PENDING.md

@@ -21,6 +21,8 @@ SDK Features
 
 SDK Enhancements
 ---
+* `internal/ini`: Normalize Section keys to lowercase ([#495](https://github.com/aws/aws-sdk-go-v2/pull/495))
+  * Update's SDK's ini utility to store all keys as lowercase. This brings the SDK inline with the AWS CLI's behavior.
 
 SDK Bugs
 ---

aws/external/shared_config_test.go

@@ -335,6 +335,16 @@ func TestLoadSharedConfigFromFile(t *testing.T) {
 				Err:      nil,
 			},
 		},
+		{
+			Profile:   "with_mixed_case_keys",
+			Expected: SharedConfig{
+				Credentials: aws.Credentials{
+					AccessKeyID:     "accessKey",
+					SecretAccessKey: "secret",
+					Source:          fmt.Sprintf("SharedConfigCredentials: %s", testConfigFilename),
+				},
+			},
+		},
 	}
 
 	for i, c := range cases {

aws/external/testdata/shared_config

@@ -84,6 +84,11 @@ s3_use_arn_region=true
 [endpoint_discovery]
 endpoint_discovery_enabled=true
 
+
+[with_mixed_case_keys]
+aWs_AcCeSs_kEy_ID = accessKey
+aWs_SecrEt_AccEsS_kEY = secret
+
 [assume_role_with_credential_source]
 role_arn = assume_role_with_credential_source_role_arn
 credential_source = Ec2InstanceMetadata

internal/ini/testdata/valid/mixed_case_keys

@@ -0,0 +1,4 @@
+[with_mixed_case_keys]
+sTring_Value = secret
+iNt_Value = 60
+flOAt_Value = 12.3

internal/ini/testdata/valid/mixed_case_keys_expected

@@ -0,0 +1,7 @@
+{
+	"with_mixed_case_keys": {
+		"int_value": 60,
+		"string_value": "secret",
+		"float_value": 12.3
+	}
+}

internal/ini/testdata/valid/utf_8_profile_expected

@@ -1,6 +1,6 @@
 {
 	"ʃʉʍΡιξ": {
-		"ϰϪϧ": "Ϯϴϖ",
+		"ϰϫϧ": "Ϯϴϖ",
 		"ϝϧ": "ϟΞ΅"
 	}
 }

internal/ini/visitor.go

@@ -3,6 +3,7 @@ package ini
 import (
 	"fmt"
 	"sort"
+	"strings"
 )
 
 // Visitor is an interface used by walkers that will
@@ -60,7 +61,7 @@ func (v *DefaultVisitor) VisitExpr(expr AST) error {
 				return err
 			}
 
-			t.values[key] = v
+			t.values[strings.ToLower(key)] = v
 		default:
 			return NewParseError(fmt.Sprintf("unsupported expression %v", expr))
 		}