diff options
| -rw-r--r-- | LICENSE | 21 | ||||
| -rw-r--r-- | README.md | 3 | ||||
| -rw-r--r-- | example.go | 17 | ||||
| -rw-r--r-- | flag.go | 119 | ||||
| -rw-r--r-- | flag_test.go | 99 | ||||
| -rw-r--r-- | go.mod | 3 |
6 files changed, 262 insertions, 0 deletions
@@ -0,0 +1,21 @@ +The MIT License (MIT) + +Copyright (c) 2022 Felix Hanley + +Permission is hereby granted, free of charge, to any person obtaining a copy of +this software and associated documentation files (the "Software"), to deal in +the Software without restriction, including without limitation the rights to +use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies +of the Software, and to permit persons to whom the Software is furnished to do +so, subject to the following conditions: + +The above copyright notice and this permission notice shall be included in all +copies or substantial portions of the Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +SOFTWARE. diff --git a/README.md b/README.md new file mode 100644 index 0000000..978b8af --- /dev/null +++ b/README.md @@ -0,0 +1,3 @@ +# Environment variables and flags + +Set flags using Go's `flag` package, and complement them with environment variables. diff --git a/example.go b/example.go new file mode 100644 index 0000000..5bffebd --- /dev/null +++ b/example.go @@ -0,0 +1,17 @@ +package envflag + +import ( + "flag" + "os" +) + +func ExampleFlag() { + flag.Bool("verbose", false, "Be verbose") + Parse() +} + +func ExampleFlagSet() { + fs := flag.NewFlagSet("example", flag.ExitOnError) + fs.Bool("verbose", false, "Be verbose") + ParseFlagSet(fs, os.Args[1:]) +} @@ -0,0 +1,119 @@ +package envflag + +import ( + "flag" + "fmt" + "os" + "regexp" + "strings" +) + +// Option type for configing the parsing. +type Option option +type option func(*config) + +// FlagConverterFunc functions are used to update flag name for envvar lookups. +type FlagConverterFunc func(flag string) string + +// UsageUpdaterFunc functions are used to update flag usage strings. +type UsageUpdaterFunc func(key, usage string) string + +type config struct { + flagConverter FlagConverterFunc + usageUpdater UsageUpdaterFunc +} + +// UsageUpdater enables configurable flag usage updates. +func UsageUpdater(f UsageUpdaterFunc) Option { + return func(cfg *config) { + cfg.usageUpdater = f + } +} + +// UsagePrefixer prefixes the flag usage with [envvar]. +func UsagePrefixer() Option { + return func(cfg *config) { + cfg.usageUpdater = usagePrefixer + } +} + +// UsageSuffixer suffixes the flag usage with [envvar]. +func UsageSuffixer() Option { + return func(cfg *config) { + cfg.usageUpdater = usageSuffixer + } +} + +// FlagConverter converts the flag name to an environment variable key. +func FlagConverter(f FlagConverterFunc) Option { + return func(cfg *config) { + cfg.flagConverter = f + } +} + +// ParseWithEnv parses the command-line flags from os.Args[1:]. Must be called +// after all flags are defined and before flags are accessed by the program. +func Parse(opts ...Option) error { + return parseFlagSetWithEnv(flag.CommandLine, os.Args[1:], opts...) +} + +// ParseFlagSetWithEnv parses flag definitions from the argument list, which +// should not include the command name. Must be called after all flags in the +// FlagSet are defined and before flags are accessed by the program. The return +// value will be ErrHelp if -help or -h were set but not defined. +func ParseFlagSet(fs *flag.FlagSet, arguments []string, opts ...Option) error { + return parseFlagSetWithEnv(fs, arguments, opts...) +} + +func parseFlagSetWithEnv(fs *flag.FlagSet, arguments []string, opts ...Option) error { + if fs.Parsed() { + return fmt.Errorf("flag has already been parsed") + } + cfg := &config{ + flagConverter: flagToEnv(), + } + for _, o := range opts { + o(cfg) + } + var nerr error + fs.VisitAll(func(f *flag.Flag) { + envKey := cfg.flagConverter(f.Name) + if cfg.usageUpdater != nil { + f.Usage = cfg.usageUpdater(envKey, f.Usage) + } + if envVal := os.Getenv(envKey); envVal != "" { + err := f.Value.Set(envVal) + if err != nil && nerr == nil { + nerr = err + } + } + }) + if nerr != nil { + return nerr + } + return fs.Parse(arguments) +} + +// convert this-format to THIS_FORMAT +func flagToEnv() func(string) string { + re := regexp.MustCompile("[^a-zA-Z0-9_]+") + return func(f string) string { + return strings.ToUpper(re.ReplaceAllLiteralString(f, "_")) + } +} + +func usageSuffixer(key, usage string) string { + envSuffix := fmt.Sprintf("[%s]", key) + if strings.HasSuffix(usage, envSuffix) { + return usage + } + return fmt.Sprintf("%s %s", usage, envSuffix) +} + +func usagePrefixer(key, usage string) string { + envPrefix := fmt.Sprintf("[%s]", key) + if strings.HasPrefix(usage, envPrefix) { + return usage + } + return fmt.Sprintf("%s %s", envPrefix, usage) +} diff --git a/flag_test.go b/flag_test.go new file mode 100644 index 0000000..bed8d8d --- /dev/null +++ b/flag_test.go @@ -0,0 +1,99 @@ +package envflag + +import ( + "flag" + "os" + "testing" +) + +func TestParseFlagSet(t *testing.T) { + tests := map[string]struct { + // Flag name + name string + // Default value + def string + // Flag command values + values []string + opts []Option + // The environment + env map[string]string + + expected string + usage string + }{ + "no flags no env default": { + name: "testing-123", + def: "defaultvalue", + expected: "defaultvalue", + }, + "flags no env no default": { + name: "testing-123", + values: []string{"-testing-123", "passed"}, + expected: "passed", + }, + "no flags env": { + name: "testing-123", + env: map[string]string{"TESTING_123": "fromenv"}, + expected: "fromenv", + }, + "flags with no env": { + name: "testing-123", + values: []string{"-testing-123", "passed"}, + expected: "passed", + }, + "flags with env": { + // Flags take precedence + name: "testing-123", + values: []string{"-testing-123", "passed"}, + env: map[string]string{"TESTING_123": "fromenv"}, + expected: "passed", + }, + "no flags with env": { + // Flags take precedence + name: "testing-123", + env: map[string]string{"TESTING_123": "fromenv"}, + expected: "fromenv", + }, + "flags with env and suffix": { + name: "testing-123", + values: []string{"-testing-123", "passed"}, + opts: []Option{UsageSuffixer()}, + env: map[string]string{"TESTING_123": "fromenv"}, + expected: "passed", + }, + "no flags with env and suffix": { + name: "testing-123", + def: "defaultvalue", + opts: []Option{UsageSuffixer()}, + env: map[string]string{"TESTING_123": "fromenv"}, + expected: "fromenv", + }, + "a variety of characters": { + // Flags take precedence + name: "tes_t.ing----123", + env: map[string]string{"TES_T_ING_123": "fromenv"}, + expected: "fromenv", + }, + } + + for name, tt := range tests { + t.Run(name, func(t *testing.T) { + fs := flag.NewFlagSet("test", flag.ExitOnError) + for k, v := range tt.env { + os.Setenv(k, v) + } + defer func() { + for k := range tt.env { + os.Unsetenv(k) + } + }() + actual := fs.String(tt.name, tt.def, "usage") + ParseFlagSet(fs, tt.values, tt.opts...) + + if *actual != tt.expected { + t.Errorf("got %q, want %q", *actual, tt.expected) + } + }) + } + +} @@ -0,0 +1,3 @@ +module userspace.com.au/envflag + +go 1.19 |