From e9f5affe7c122be27aa1ddc3dfd7c641efa65b76 Mon Sep 17 00:00:00 2001
From: Dean Davidson <deand@sembit.com>
Date: Sun, 30 Mar 2025 11:26:42 -0700
Subject: [PATCH] Trim whitespace by default

---
 README.md         |  4 ++--
 dotconfig.go      | 16 ++++++++++++----
 dotconfig_test.go | 22 ++++++++++++++++++++++
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index 440e9eb..898642d 100644
--- a/README.md
+++ b/README.md
@@ -109,6 +109,6 @@ if err != nil {
 ```
 
 ## Contributing
-Contributions are always welcome. Have a new idea or find a bug? Submit a pull request or create an issue!
+Contributions are always welcome. Have a new idea or find a bug? Submit a pull request or create an issue! 
 
-**IMPORTANT**: This package is being used in production and any future updates should maintain backwards compatibility.
\ No newline at end of file
+This package is being used in production and any future updates should maintain backwards compatibility. This is why we have options; to allow us to introduce optional new features while maintaining backwards compatibility.
\ No newline at end of file
diff --git a/dotconfig.go b/dotconfig.go
index b536416..d611d71 100644
--- a/dotconfig.go
+++ b/dotconfig.go
@@ -18,11 +18,13 @@ type DecodeOption int
 const (
 	ReturnFileIOErrors DecodeOption = iota // Return file IO errors
 	EnforceStructTags                      // Make sure all fields in config struct have `env` struct tags
+	AllowWhitespace                        // Allow leading/trailing whitespace in string values
 )
 
 type options struct {
 	ReturnFileIOErrors bool
 	EnforceStructTags  bool
+	AllowWhitespace    bool
 }
 
 func optsFromVariadic(opts []DecodeOption) options {
@@ -33,6 +35,8 @@ func optsFromVariadic(opts []DecodeOption) options {
 			v.ReturnFileIOErrors = true
 		case EnforceStructTags:
 			v.EnforceStructTags = true
+		case AllowWhitespace:
+			v.AllowWhitespace = true
 		}
 	}
 	return v
@@ -169,7 +173,7 @@ func fromEnv[T any](opts options) (T, error) {
 			continue
 		}
 		// Parse env tag into environment variable key and options
-		envKey, opts := parseTag(envTag)
+		envKey, tagOpts := parseTag(envTag)
 		envValue, keyExists := os.LookupEnv(envKey)
 		// Missing env var
 		if !keyExists {
@@ -177,7 +181,7 @@ func fromEnv[T any](opts options) (T, error) {
 			defaultVal := fieldType.Tag.Get("default")
 			if defaultVal != "" {
 				envValue = defaultVal
-			} else if opts.Contains("optional") {
+			} else if tagOpts.Contains("optional") {
 				// Optional so skip missing error
 				continue
 			} else {
@@ -185,10 +189,14 @@ func fromEnv[T any](opts options) (T, error) {
 				continue
 			}
 		}
+		// If the consumer hasn't explicitely allowed whitespace, we trim it by default
+		if !opts.AllowWhitespace {
+			envValue = strings.TrimSpace(envValue)
+		}
 		// Empty value
-		if strings.TrimSpace(envValue) == "" {
+		if envValue == "" {
 			// If required option is set, this is an error
-			if opts.Contains("required") {
+			if tagOpts.Contains("required") {
 				errs.Add(fmt.Errorf("%w: %v", ErrMissingRequiredField, envKey))
 			}
 			// Otherwise zero-values are fine
diff --git a/dotconfig_test.go b/dotconfig_test.go
index 43650be..d92c2ba 100644
--- a/dotconfig_test.go
+++ b/dotconfig_test.go
@@ -214,3 +214,25 @@ func TestFileIO(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+type testAllowWhitespace struct {
+	Value string `env:"WHITESPACE_VALUE"`
+}
+
+func TestAllowWhitespace(t *testing.T) {
+	os.Setenv("WHITESPACE_VALUE", " whitespace ")
+	config, err := dotconfig.FromFileName[testAllowWhitespace]("doesn't exist")
+	if err != nil {
+		t.Errorf("Wasnt't expecting error. Got: %v", err)
+	}
+	if config.Value != "whitespace" {
+		t.Error("Expected to trim whitespace.")
+	}
+	config, err = dotconfig.FromFileName[testAllowWhitespace]("doesn't exist", dotconfig.AllowWhitespace)
+	if err != nil {
+		t.Errorf("Wasnt't expecting error. Got: %v", err)
+	}
+	if config.Value != " whitespace " {
+		t.Error("Expected to allow whitespace.")
+	}
+}