refactor: enable gocritic linter and fix lint issues

.golangci.yml

@@ -1,4 +1,13 @@
 linters-settings:
+  gocritic:
+    enabled-checks:
+      - emptyStringTest
+      - evalOrder
+      - paramTypeCombine
+      - preferStringWriter
+      - sprintfQuotedString
+      - stringConcatSimplify
+      - unnamedResult
   revive:
     rules:
       - name: line-length-limit
@@ -15,6 +24,7 @@ linters:
   enable:
     - thelper
     - gofumpt
+    - gocritic
     - tparallel
     - unconvert
     - unparam

env.go

@@ -263,14 +263,16 @@ func ParseWithOptions(v interface{}, opts Options) error {
 // values from environment variables.
 func ParseAs[T any]() (T, error) {
 	var t T
-	return t, Parse(&t)
+	err := Parse(&t)
+	return t, err
 }
 
 // ParseWithOptions parses the given struct type containing `env` tags and
 // loads its values from environment variables.
 func ParseAsWithOptions[T any](opts Options) (T, error) {
 	var t T
-	return t, ParseWithOptions(&t, opts)
+	err := ParseWithOptions(&t, opts)
+	return t, err
 }
 
 // Must panic is if err is not nil, and returns t otherwise.
@@ -603,7 +605,7 @@ func get(fieldParams FieldParams, opts Options) (val string, err error) {
 		defer os.Unsetenv(fieldParams.Key)
 	}
 
-	if fieldParams.Required && !exists && len(fieldParams.OwnKey) > 0 {
+	if fieldParams.Required && !exists && fieldParams.OwnKey != "" {
 		return "", newVarIsNotSetError(fieldParams.Key)
 	}
 
@@ -628,7 +630,7 @@ func get(fieldParams FieldParams, opts Options) (val string, err error) {
 }
 
 // split the env tag's key into the expected key and desired option, if any.
-func parseKeyForOption(key string) (string, []string) {
+func parseKeyForOption(key string) (ownKey string, tags []string) {
 	opts := strings.Split(key, ",")
 	return opts[0], opts[1:]
 }
@@ -638,7 +640,7 @@ func getFromFile(filename string) (value string, err error) {
 	return string(b), err
 }
 
-func getOr(key, defaultValue string, defExists bool, envs map[string]string) (val string, exists bool, isDefault bool) {
+func getOr(key, defaultValue string, defExists bool, envs map[string]string) (val string, exists, isDefault bool) {
 	value, exists := envs[key]
 	switch {
 	case (!exists || key == "") && defExists:

env_test.go

@@ -276,7 +276,7 @@ func TestParsesEnv(t *testing.T) {
 	t.Setenv("URL", tos(url1))
 	t.Setenv("URLS", toss(url1, url2))
 
-	t.Setenv("SEPSTRINGS", strings.Join([]string{str1, str2}, ":"))
+	t.Setenv("SEPSTRINGS", str1+":"+str2)
 
 	nonDefinedStr := "nonDefinedStr"
 	t.Setenv("NONDEFINED_STR", nonDefinedStr)
@@ -1485,7 +1485,7 @@ func TestFileBadFile(t *testing.T) {
 	}
 
 	err := Parse(&config{})
-	isErrorWithMessage(t, err, fmt.Sprintf(`env: could not load content of file "%s" from variable SECRET_KEY: open %s: %s`, filename, filename, oserr))
+	isErrorWithMessage(t, err, fmt.Sprintf("env: could not load content of file %q from variable SECRET_KEY: open %s: %s", filename, filename, oserr))
 	isTrue(t, errors.Is(err, LoadFileContentError{}))
 }
 

error.go

@@ -68,7 +68,7 @@ func newParseError(sf reflect.StructField, err error) error {
 }
 
 func (e ParseError) Error() string {
-	return fmt.Sprintf(`parse error on field "%s" of type "%s": %v`, e.Name, e.Type, e.Err)
+	return fmt.Sprintf("parse error on field %q of type %q: %v", e.Name, e.Type, e.Err)
 }
 
 // The error occurs when pass something that is not a pointer to a struct to Parse
@@ -89,7 +89,7 @@ func newNoParserError(sf reflect.StructField) error {
 }
 
 func (e NoParserError) Error() string {
-	return fmt.Sprintf(`no parser found for field "%s" of type "%s"`, e.Name, e.Type)
+	return fmt.Sprintf("no parser found for field %q of type %q", e.Name, e.Type)
 }
 
 // This error occurs when the given tag is not supported.
@@ -109,7 +109,7 @@ func (e NoSupportedTagOptionError) Error() string {
 
 // This error occurs when the required variable is not set.
 //
-// deprecated: use VarIsNotSetError
+// Deprecated: use VarIsNotSetError.
 type EnvVarIsNotSetError = VarIsNotSetError
 
 // This error occurs when the required variable is not set.
@@ -127,7 +127,7 @@ func (e VarIsNotSetError) Error() string {
 
 // This error occurs when the variable which must be not empty is existing but has an empty value
 //
-// deprecated: use EmptyVarError
+// Deprecated: use EmptyVarError.
 type EmptyEnvVarError = EmptyVarError
 
 // This error occurs when the variable which must be not empty is existing but has an empty value
@@ -155,7 +155,7 @@ func newLoadFileContentError(filename, key string, err error) error {
 }
 
 func (e LoadFileContentError) Error() string {
-	return fmt.Sprintf(`could not load content of file "%s" from variable %s: %v`, e.Filename, e.Key, e.Err)
+	return fmt.Sprintf("could not load content of file %q from variable %s: %v", e.Filename, e.Key, e.Err)
 }
 
 // This error occurs when it's impossible to convert value using given parser.

example_test.go

@@ -3,7 +3,6 @@ package env
 import (
 	"errors"
 	"fmt"
-	"io"
 	"os"
 	"reflect"
 )
@@ -400,7 +399,7 @@ func ExampleParseWithOptions_useFieldName() {
 // it.
 func ExampleParse_fromFile() {
 	f, _ := os.CreateTemp("", "")
-	_, _ = io.WriteString(f, "super secret")
+	_, _ = f.WriteString("super secret")
 	_ = f.Close()
 
 	type Config struct {