Resolve environments case-insensitively on Windows

types/config.go

@@ -18,10 +18,17 @@ package types
 
 import (
 	"encoding/json"
+	"runtime"
+	"strings"
 
 	"github.com/mitchellh/mapstructure"
 )
 
+var (
+	// isCaseInsensitiveEnvVars is true on platforms where environment variable names are treated case-insensitively.
+	isCaseInsensitiveEnvVars = (runtime.GOOS == "windows")
+)
+
 // ConfigDetails are the details about a group of ConfigFiles
 type ConfigDetails struct {
 	Version     string
@@ -33,7 +40,21 @@ type ConfigDetails struct {
 // LookupEnv provides a lookup function for environment variables
 func (cd ConfigDetails) LookupEnv(key string) (string, bool) {
 	v, ok := cd.Environment[key]
-	return v, ok
+	if !isCaseInsensitiveEnvVars || ok {
+		return v, ok
+	}
+	// variable names must be treated case-insensitively on some platforms (that is, Windows).
+	// Resolves in this way:
+	// * Return the value if its name matches with the passed name case-sensitively.
+	// * Otherwise, return the value if its lower-cased name matches lower-cased passed name.
+	//     * The value is indefinite if multiple variables match.
+	lowerKey := strings.ToLower(key)
+	for k, v := range cd.Environment {
+		if strings.ToLower(k) == lowerKey {
+			return v, true
+		}
+	}
+	return "", false
 }
 
 // ConfigFile is a filename and the contents of the file as a Dict

types/config_test.go

@@ -53,3 +53,102 @@ func Test_WithServices(t *testing.T) {
 	assert.NilError(t, err)
 	assert.DeepEqual(t, order, []string{"service_2", "service_3", "service_1"})
 }
+
+func Test_LookupEnv(t *testing.T) {
+	tests := []struct {
+		name            string
+		environment     map[string]string
+		caseInsensitive bool
+		search          string
+		expectedValue   string
+		expectedOk      bool
+	}{
+		{
+			name: "case sensitive/case match",
+			environment: map[string]string{
+				"Env1": "Value1",
+				"Env2": "Value2",
+			},
+			caseInsensitive: false,
+			search:          "Env1",
+			expectedValue:   "Value1",
+			expectedOk:      true,
+		},
+		{
+			name: "case sensitive/case unmatch",
+			environment: map[string]string{
+				"Env1": "Value1",
+				"Env2": "Value2",
+			},
+			caseInsensitive: false,
+			search:          "ENV1",
+			expectedValue:   "",
+			expectedOk:      false,
+		},
+		{
+			name:            "case sensitive/nil environment",
+			environment:     nil,
+			caseInsensitive: false,
+			search:          "Env1",
+			expectedValue:   "",
+			expectedOk:      false,
+		},
+		{
+			name: "case insensitive/case match",
+			environment: map[string]string{
+				"Env1": "Value1",
+				"Env2": "Value2",
+			},
+			caseInsensitive: true,
+			search:          "Env1",
+			expectedValue:   "Value1",
+			expectedOk:      true,
+		},
+		{
+			name: "case insensitive/case unmatch",
+			environment: map[string]string{
+				"Env1": "Value1",
+				"Env2": "Value2",
+			},
+			caseInsensitive: true,
+			search:          "ENV1",
+			expectedValue:   "Value1",
+			expectedOk:      true,
+		},
+		{
+			name: "case insensitive/unmatch",
+			environment: map[string]string{
+				"Env1": "Value1",
+				"Env2": "Value2",
+			},
+			caseInsensitive: true,
+			search:          "Env3",
+			expectedValue:   "",
+			expectedOk:      false,
+		},
+		{
+			name:            "case insensitive/nil environment",
+			environment:     nil,
+			caseInsensitive: true,
+			search:          "Env1",
+			expectedValue:   "",
+			expectedOk:      false,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			origIsCaseInsensitiveEnvVars := isCaseInsensitiveEnvVars
+			defer func() {
+				isCaseInsensitiveEnvVars = origIsCaseInsensitiveEnvVars
+			}()
+			isCaseInsensitiveEnvVars = test.caseInsensitive
+			cd := ConfigDetails{
+				Environment: test.environment,
+			}
+			v, ok := cd.LookupEnv(test.search)
+			assert.Equal(t, v, test.expectedValue)
+			assert.Equal(t, ok, test.expectedOk)
+		})
+	}
+}