Add JSON InputSource to altsrc package

- Implement NewJSONSource* functions for returning an InputSource from
   various JSON data sources.
 - Copy and modify YAML tests for the JSON InputSource

README.md

@@ -547,9 +547,9 @@ the yaml input source for any flags that are defined on that command.  As a note
 the "load" flag used would also have to be defined on the command flags in order
 for this code snipped to work.
 
-Currently only YAML files are supported but developers can add support for other
+Currently only YAML and JSON files are supported but developers can add support
-input sources by implementing the altsrc.InputSourceContext for their given
+for other input sources by implementing the altsrc.InputSourceContext for their
-sources.
+given sources.
 
 Here is a more complete sample of a command using YAML support:
 

altsrc/json_command_test.go

@@ -0,0 +1,324 @@
+package altsrc
+
+import (
+	"flag"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/urfave/cli"
+)
+
+const (
+	fileName   = "current.json"
+	simpleJSON = `{"test": 15}`
+	nestedJSON = `{"top": {"test": 15}}`
+)
+
+func TestCommandJSONFileTest(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, simpleJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	test := []string{"test-cmd", "--load", fileName}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val := c.Int("test")
+			expect(t, val, 15)
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(&cli.IntFlag{Name: "test"}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandJSONFileTestGlobalEnvVarWins(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, simpleJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	os.Setenv("THE_TEST", "10")
+	defer os.Setenv("THE_TEST", "")
+
+	test := []string{"test-cmd", "--load", fileName}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val := c.Int("test")
+			expect(t, val, 10)
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(&cli.IntFlag{Name: "test", EnvVars: []string{"THE_TEST"}}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandJSONFileTestGlobalEnvVarWinsNested(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, nestedJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	os.Setenv("THE_TEST", "10")
+	defer os.Setenv("THE_TEST", "")
+
+	test := []string{"test-cmd", "--load", fileName}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val := c.Int("top.test")
+			expect(t, val, 10)
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(&cli.IntFlag{Name: "top.test", EnvVars: []string{"THE_TEST"}}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandJSONFileTestSpecifiedFlagWins(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, simpleJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	test := []string{"test-cmd", "--load", fileName, "--test", "7"}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val := c.Int("test")
+			expect(t, val, 7)
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(&cli.IntFlag{Name: "test"}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandJSONFileTestSpecifiedFlagWinsNested(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, nestedJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	test := []string{"test-cmd", "--load", fileName, "--top.test", "7"}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val := c.Int("top.test")
+			expect(t, val, 7)
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(&cli.IntFlag{Name: "top.test"}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandJSONFileTestDefaultValueFileWins(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, simpleJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	test := []string{"test-cmd", "--load", fileName}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val := c.Int("test")
+			expect(t, val, 15)
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(&cli.IntFlag{Name: "test", Value: 7}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandJSONFileTestDefaultValueFileWinsNested(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, nestedJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	test := []string{"test-cmd", "--load", fileName}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val := c.Int("top.test")
+			expect(t, val, 15)
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(&cli.IntFlag{Name: "top.test", Value: 7}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandJSONFileFlagHasDefaultGlobalEnvJSONSetGlobalEnvWins(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, simpleJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	os.Setenv("THE_TEST", "11")
+	defer os.Setenv("THE_TEST", "")
+
+	test := []string{"test-cmd", "--load", fileName}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val := c.Int("test")
+			expect(t, val, 11)
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(&cli.IntFlag{Name: "test", Value: 7, EnvVars: []string{"THE_TEST"}}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandJSONFileFlagHasDefaultGlobalEnvJSONSetGlobalEnvWinsNested(t *testing.T) {
+	cleanup := writeTempFile(t, fileName, nestedJSON)
+	defer cleanup()
+
+	app := &cli.App{}
+	set := flag.NewFlagSet("test", 0)
+	os.Setenv("THE_TEST", "11")
+	defer os.Setenv("THE_TEST", "")
+
+	test := []string{"test-cmd", "--load", fileName}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) error {
+			val := c.Int("top.test")
+			expect(t, val, 11)
+			return nil
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(&cli.IntFlag{Name: "top.test", Value: 7, EnvVars: []string{"THE_TEST"}}),
+			&cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewJSONSourceFromFlagFunc("load"))
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func writeTempFile(t *testing.T, name string, content string) func() {
+	if err := ioutil.WriteFile(name, []byte(content), 0666); err != nil {
+		t.Fatalf("cannot write %q: %v", name, err)
+	}
+	return func() {
+		if err := os.Remove(name); err != nil {
+			t.Errorf("cannot remove %q: %v", name, err)
+		}
+	}
+}

altsrc/json_source_context.go

@@ -0,0 +1,202 @@
+package altsrc
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"strings"
+	"time"
+
+	"github.com/urfave/cli"
+)
+
+// NewJSONSourceFromFlagFunc returns a func that takes a cli.Context
+// and returns an InputSourceContext suitable for retrieving config
+// variables from a file containing JSON data with the file name defined
+// by the given flag.
+func NewJSONSourceFromFlagFunc(flag string) func(c *cli.Context) (InputSourceContext, error) {
+	return func(context *cli.Context) (InputSourceContext, error) {
+		return NewJSONSourceFromFile(context.String(flag))
+	}
+}
+
+// NewJSONSourceFromFile returns an InputSourceContext suitable for
+// retrieving config variables from a file (or url) containing JSON
+// data.
+func NewJSONSourceFromFile(f string) (InputSourceContext, error) {
+	data, err := loadDataFrom(f)
+	if err != nil {
+		return nil, err
+	}
+	return NewJSONSource(data)
+}
+
+// NewJSONSourceFromReader returns an InputSourceContext suitable for
+// retrieving config variables from an io.Reader that returns JSON data.
+func NewJSONSourceFromReader(r io.Reader) (InputSourceContext, error) {
+	data, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+	return NewJSONSource(data)
+}
+
+// NewJSONSource returns an InputSourceContext suitable for retrieving
+// config variables from raw JSON data.
+func NewJSONSource(data []byte) (InputSourceContext, error) {
+	var deserialized map[string]interface{}
+	if err := json.Unmarshal(data, &deserialized); err != nil {
+		return nil, err
+	}
+	return &jsonSource{deserialized: deserialized}, nil
+}
+
+func (x *jsonSource) Int(name string) (int, error) {
+	i, err := x.getValue(name)
+	if err != nil {
+		return 0, err
+	}
+	switch v := i.(type) {
+	default:
+		return 0, fmt.Errorf("unexpected type %T for %q", i, name)
+	case int:
+		return v, nil
+	case float64:
+		return int(float64(v)), nil
+	case float32:
+		return int(float32(v)), nil
+	}
+}
+
+func (x *jsonSource) Duration(name string) (time.Duration, error) {
+	i, err := x.getValue(name)
+	if err != nil {
+		return 0, err
+	}
+	v, ok := (time.Duration)(0), false
+	if v, ok = i.(time.Duration); !ok {
+		return v, fmt.Errorf("unexpected type %T for %q", i, name)
+	}
+	return v, nil
+}
+
+func (x *jsonSource) Float64(name string) (float64, error) {
+	i, err := x.getValue(name)
+	if err != nil {
+		return 0, err
+	}
+	v, ok := (float64)(0), false
+	if v, ok = i.(float64); !ok {
+		return v, fmt.Errorf("unexpected type %T for %q", i, name)
+	}
+	return v, nil
+}
+
+func (x *jsonSource) String(name string) (string, error) {
+	i, err := x.getValue(name)
+	if err != nil {
+		return "", err
+	}
+	v, ok := "", false
+	if v, ok = i.(string); !ok {
+		return v, fmt.Errorf("unexpected type %T for %q", i, name)
+	}
+	return v, nil
+}
+
+func (x *jsonSource) StringSlice(name string) ([]string, error) {
+	i, err := x.getValue(name)
+	if err != nil {
+		return nil, err
+	}
+	switch v := i.(type) {
+	default:
+		return nil, fmt.Errorf("unexpected type %T for %q", i, name)
+	case []string:
+		return v, nil
+	case []interface{}:
+		c := []string{}
+		for _, s := range v {
+			if str, ok := s.(string); ok {
+				c = append(c, str)
+			} else {
+				return c, fmt.Errorf("unexpected item type %T in %T for %q", s, c, name)
+			}
+		}
+		return c, nil
+	}
+}
+
+func (x *jsonSource) IntSlice(name string) ([]int, error) {
+	i, err := x.getValue(name)
+	if err != nil {
+		return nil, err
+	}
+	switch v := i.(type) {
+	default:
+		return nil, fmt.Errorf("unexpected type %T for %q", i, name)
+	case []int:
+		return v, nil
+	case []interface{}:
+		c := []int{}
+		for _, s := range v {
+			if i2, ok := s.(int); ok {
+				c = append(c, i2)
+			} else {
+				return c, fmt.Errorf("unexpected item type %T in %T for %q", s, c, name)
+			}
+		}
+		return c, nil
+	}
+}
+
+func (x *jsonSource) Generic(name string) (cli.Generic, error) {
+	i, err := x.getValue(name)
+	if err != nil {
+		return nil, err
+	}
+	v, ok := (cli.Generic)(nil), false
+	if v, ok = i.(cli.Generic); !ok {
+		return v, fmt.Errorf("unexpected type %T for %q", i, name)
+	}
+	return v, nil
+}
+
+func (x *jsonSource) Bool(name string) (bool, error) {
+	i, err := x.getValue(name)
+	if err != nil {
+		return false, err
+	}
+	v, ok := false, false
+	if v, ok = i.(bool); !ok {
+		return v, fmt.Errorf("unexpected type %T for %q", i, name)
+	}
+	return v, nil
+}
+
+func (x *jsonSource) getValue(key string) (interface{}, error) {
+	return jsonGetValue(key, x.deserialized)
+}
+
+func jsonGetValue(key string, m map[string]interface{}) (interface{}, error) {
+	var ret interface{}
+	var ok bool
+	working := m
+	keys := strings.Split(key, ".")
+	for ix, k := range keys {
+		if ret, ok = working[k]; !ok {
+			return ret, fmt.Errorf("missing key %q", key)
+		}
+		if working, ok = ret.(map[string]interface{}); !ok {
+			if ix < len(keys)-1 {
+				return ret, fmt.Errorf("unexpected intermediate value at %q segment of %q: %T", k, key, ret)
+			}
+		}
+	}
+	return ret, nil
+}
+
+type jsonSource struct {
+	deserialized map[string]interface{}
+}