feat: Add parsing for netip and net.HardwareAddr types (#197)

This change expands the `getenv` package to support `netip.Addr`, `netip.Prefix`, and `net.HardwareAddr` types, along with their slice forms, significantly increasing the utility for network-related configurations.

Error reporting for `ErrInvalidValue` is improved by wrapping the underlying parsing errors, providing more detailed diagnostics. A new `publicError` type is introduced to allow `errors.Is` checks against package sentinels while retaining the original error cause. Slice parsing error handling is also made more consistent.

Additionally, the styling script `fmt.sh` now uses `gofmt` instead of `gofumpt`.

Author: obalunenko

README.md

@@ -50,6 +50,12 @@ Types supported:
 - []url.URL
 - net.IP
 - []net.IP
+- netip.Addr
+- []netip.Addr
+- netip.Prefix
+- []netip.Prefix
+- net.HardwareAddr
+- []net.HardwareAddr
 - complex64
 - []complex64
 - complex128
@@ -190,11 +196,11 @@ Output:
 ```
 [string]: golly; err: <nil>
 [int]: 123; err: <nil>
-[int]: 0; err: could not parse variable[GH_GETENV_TEST] value[123s4] to type[int]: invalid value
+[int]: 0; err: failed to parse environment variable[GH_GETENV_TEST]: strconv.ParseInt: parsing "123s4": invalid syntax: invalid value
 [time.Time]: 2022-01-20 00:00:00 +0000 UTC; err: <nil>
 [[]float64]: [26.89 0.67]; err: <nil>
 [time.Duration]: 2h35m0s; err: <nil>
-[url.URL]: {https  test:abcd123 golangbyexample.com:8000 /tutorials/intro  false false type=advance&compact=false history }; err: <nil>
+[url.URL]: https://test:abcd123@golangbyexample.com:8000/tutorials/intro?type=advance&compact=false#history; err: <nil>
 [net.IP]: 2001:cb8::17; err: <nil>
 [[]string]: [a b c d]; err: <nil>
 [complex128]: (1+2i); err: <nil>
@@ -332,7 +338,7 @@ Output:
 [time.Time]: 2022-01-20 00:00:00 +0000 UTC
 [[]float64]: [26.89 0.67]
 [time.Duration]: 2h35m0s
-[url.URL]: {https  test:abcd123 golangbyexample.com:8000 /tutorials/intro  false false type=advance&compact=false history }
+[url.URL]: https://test:abcd123@golangbyexample.com:8000/tutorials/intro?type=advance&compact=false#history
 [net.IP]: 2001:cb8::17
 [[]string]: [a b c d]
 [complex128]: (1+2i)

getenv.go

@@ -41,6 +41,12 @@
 // - []url.URL
 // - net.IP
 // - []net.IP
+// - netip.Addr
+// - []netip.Addr
+// - netip.Prefix
+// - []netip.Prefix
+// - net.HardwareAddr
+// - []net.HardwareAddr
 // - complex64
 // - []complex64
 // - complex128
@@ -75,11 +81,17 @@ func Env[T internal.EnvParsable](key string, options ...option.Option) (T, error
 	val, err := w.ParseEnv(key, params)
 	if err != nil {
 		if errors.Is(err, internal.ErrNotSet) {
-			return t, fmt.Errorf("failed to get environment variable[%s]: %w", key, ErrNotSet)
+			return t, fmt.Errorf("failed to get environment variable[%s]: %w", key, publicError{
+				cause:    err,
+				sentinel: ErrNotSet,
+			})
 		}
 
 		if errors.Is(err, internal.ErrInvalidValue) {
-			return t, fmt.Errorf("failed to parse environment variable[%s]: %w", key, ErrInvalidValue)
+			return t, fmt.Errorf("failed to parse environment variable[%s]: %w", key, publicError{
+				cause:    err,
+				sentinel: ErrInvalidValue,
+			})
 		}
 
 		return t, fmt.Errorf("failed to parse environment variable[%s]: %w", key, err)
@@ -106,6 +118,20 @@ func EnvOrDefault[T internal.EnvParsable](key string, defaultVal T, options ...o
 	return val
 }
 
+// publicError keeps parser details while matching exported sentinels.
+type publicError struct {
+	cause    error
+	sentinel error
+}
+
+func (e publicError) Error() string {
+	return e.cause.Error()
+}
+
+func (e publicError) Unwrap() []error {
+	return []error{e.cause, e.sentinel}
+}
+
 // newParseParams creates new parameters from options.
 func newParseParams(opts []option.Option) internal.Parameters {
 	var p internal.Parameters

getenv_example_test.go

@@ -241,7 +241,7 @@ func ExampleEnv() {
 	// Output:
 	// [string]: golly; err: <nil>
 	// [int]: 123; err: <nil>
-	// [int]: 0; err: failed to parse environment variable[GH_GETENV_TEST]: invalid value
+	// [int]: 0; err: failed to parse environment variable[GH_GETENV_TEST]: strconv.ParseInt: parsing "123s4": invalid syntax: invalid value
 	// [time.Time]: 2022-01-20 00:00:00 +0000 UTC; err: <nil>
 	// [[]float64]: [26.89 0.67]; err: <nil>
 	// [time.Duration]: 2h35m0s; err: <nil>