From 5c247b6f2907e8c4da5a66fa2192fcba95e100f2 Mon Sep 17 00:00:00 2001 From: Brian Picciano Date: Thu, 5 May 2022 20:17:59 -0600 Subject: Refactor cfg to use envvars as well --- srv/cfg/cfg.go | 146 ++++++++++++++++++++++++++++++++++++++++++++++++---- srv/cfg/cfg_test.go | 46 +++++++++++++++++ 2 files changed, 181 insertions(+), 11 deletions(-) create mode 100644 srv/cfg/cfg_test.go (limited to 'srv/cfg') diff --git a/srv/cfg/cfg.go b/srv/cfg/cfg.go index 685248c..8513e16 100644 --- a/srv/cfg/cfg.go +++ b/srv/cfg/cfg.go @@ -5,7 +5,10 @@ package cfg import ( "context" "flag" + "fmt" "os" + "strconv" + "strings" ) // Cfger is a component which can be used with Cfg to setup its initialization. @@ -13,20 +16,70 @@ type Cfger interface { SetupCfg(*Cfg) } +// Params are used to initialize a Cfg instance. +type Params struct { + + // Args are the command line arguments, excluding the command-name. + // + // Defaults to os.Args[1:] + Args []string + + // Env is the process's environment variables. + // + // Defaults to the real environment variables. + Env map[string]string + + // EnvPrefix indicates a string to prefix to all environment variable names + // that Cfg will read. Will be automatically suffixed with a "_" if given. + EnvPrefix string +} + +func (p Params) withDefaults() Params { + + if p.Args == nil { + p.Args = os.Args[1:] + } + + if p.Env == nil { + + p.Env = map[string]string{} + + for _, envVar := range os.Environ() { + + parts := strings.SplitN(envVar, "=", 2) + + if len(parts) < 2 { + panic(fmt.Sprintf("envVar %q returned from os.Environ() somehow", envVar)) + } + + p.Env[parts[0]] = parts[1] + } + } + + if p.EnvPrefix != "" { + p.EnvPrefix = strings.TrimSuffix(p.EnvPrefix, "_") + "_" + } + + return p +} + // Cfg is a wrapper around the stdlib's FlagSet and a set of initialization // hooks. type Cfg struct { - *flag.FlagSet + params Params + flagSet *flag.FlagSet hooks []func(ctx context.Context) error - args []string } // New initializes and returns a new instance of *Cfg. -func New() *Cfg { +func New(params Params) *Cfg { + + params = params.withDefaults() + return &Cfg{ - FlagSet: flag.NewFlagSet("", flag.ExitOnError), - args: os.Args[1:], + params: params, + flagSet: flag.NewFlagSet("", flag.ExitOnError), } } @@ -40,7 +93,7 @@ func (c *Cfg) OnInit(cb func(context.Context) error) { // called. If one returns an error that error is returned and no further hooks // are run. func (c *Cfg) Init(ctx context.Context) error { - if err := c.FlagSet.Parse(c.args); err != nil { + if err := c.flagSet.Parse(c.params.Args); err != nil { return err } @@ -53,6 +106,77 @@ func (c *Cfg) Init(ctx context.Context) error { return nil } +func (c *Cfg) envifyName(name string) string { + name = c.params.EnvPrefix + name + name = strings.Replace(name, "-", "_", -1) + name = strings.ToUpper(name) + return name +} + +func envifyUsage(envName, usage string) string { + return fmt.Sprintf("%s (overrides %s)", usage, envName) +} + +// StringVar is equivalent to flag.FlagSet's StringVar method, but will +// additionally set up an environment variable for the parameter. +func (c *Cfg) StringVar(p *string, name, value, usage string) { + + envName := c.envifyName(name) + + c.flagSet.StringVar(p, name, value, envifyUsage(envName, usage)) + + if val := c.params.Env[envName]; val != "" { + *p = val + } +} + +// String is equivalent to flag.FlagSet's String method, but will additionally +// set up an environment variable for the parameter. +func (c *Cfg) String(name, value, usage string) *string { + p := new(string) + c.StringVar(p, name, value, usage) + return p +} + +// IntVar is equivalent to flag.FlagSet's IntVar method, but will additionally +// set up an environment variable for the parameter. +func (c *Cfg) IntVar(p *int, name string, value int, usage string) { + + envName := c.envifyName(name) + + c.flagSet.IntVar(p, name, value, envifyUsage(envName, usage)) + + // if we can't parse the envvar now then just hold onto the error until + // Init, otherwise we'd have to panic here and that'd be ugly. + var err error + + if valStr := c.params.Env[envName]; valStr != "" { + + var val int + val, err = strconv.Atoi(valStr) + + if err != nil { + err = fmt.Errorf( + "parsing envvar %q with value %q: %w", + envName, valStr, err, + ) + + } else { + *p = val + } + } + + c.OnInit(func(context.Context) error { return err }) +} + +// Int is equivalent to flag.FlagSet's Int method, but will additionally set up +// an environment variable for the parameter. +func (c *Cfg) Int(name string, value int, usage string) *int { + p := new(int) + c.IntVar(p, name, value, usage) + return p +} + // SubCmd should be called _after_ Init. Init will have consumed all arguments // up until the first non-flag argument. This non-flag argument is a // sub-command, and is returned by this method. This method also resets Cfg's @@ -61,16 +185,16 @@ func (c *Cfg) Init(ctx context.Context) error { // If there is no sub-command following the initial set of flags then this will // return empty string. func (c *Cfg) SubCmd() string { - c.args = c.FlagSet.Args() - if len(c.args) == 0 { + c.params.Args = c.flagSet.Args() + if len(c.params.Args) == 0 { return "" } - subCmd := c.args[0] + subCmd := c.params.Args[0] - c.FlagSet = flag.NewFlagSet(subCmd, flag.ExitOnError) + c.flagSet = flag.NewFlagSet(subCmd, flag.ExitOnError) c.hooks = nil - c.args = c.args[1:] + c.params.Args = c.params.Args[1:] return subCmd } diff --git a/srv/cfg/cfg_test.go b/srv/cfg/cfg_test.go new file mode 100644 index 0000000..7ccf94a --- /dev/null +++ b/srv/cfg/cfg_test.go @@ -0,0 +1,46 @@ +package cfg + +import ( + "context" + "testing" + + "github.com/stretchr/testify/assert" +) + +func TestStringVar(t *testing.T) { + + cfg := New(Params{ + Args: []string{"--foo=CLI"}, + Env: map[string]string{"FOO": "ENV", "BAR": "ENV"}, + }) + + var foo, bar, baz string + + cfg.StringVar(&foo, "foo", "DEF", "") + cfg.StringVar(&bar, "bar", "DEF", "") + cfg.StringVar(&baz, "baz", "DEF", "") + + assert.NoError(t, cfg.Init(context.Background())) + assert.Equal(t, "CLI", foo) + assert.Equal(t, "ENV", bar) + assert.Equal(t, "DEF", baz) +} + +func TestIntVar(t *testing.T) { + + cfg := New(Params{ + Args: []string{"--foo=111"}, + Env: map[string]string{"FOO": "222", "BAR": "222"}, + }) + + var foo, bar, baz int + + cfg.IntVar(&foo, "foo", 333, "") + cfg.IntVar(&bar, "bar", 333, "") + cfg.IntVar(&baz, "baz", 333, "") + + assert.NoError(t, cfg.Init(context.Background())) + assert.Equal(t, 111, foo) + assert.Equal(t, 222, bar) + assert.Equal(t, 333, baz) +} -- cgit v1.2.3