Add support for TOML tables to fftoml package (#48)

* Add support for TOML tables to fftoml package

* Make fftoml flag name separator configurable

* Export fftoml config as ConfigFileParser and rename FlagSeparator as TableDelimeter

* Update fftoml/fftoml_test.go

Restructure call to ff.Parse

Co-Authored-By: Peter Bourgon <peterbourgon@users.noreply.github.com>

* Correct Delimeter -> Delimiter typo in fftoml package

fftoml/fftoml.go

@@ -6,27 +6,86 @@ import (
 	"io"
 	"strconv"
 
-	"github.com/BurntSushi/toml"
+	"github.com/pelletier/go-toml"
 	"github.com/peterbourgon/ff"
 )
 
 // Parser is a parser for TOML file format. Flags and their values are read
 // from the key/value pairs defined in the config file.
 func Parser(r io.Reader, set func(name, value string) error) error {
-	var m map[string]interface{}
-	_, err := toml.DecodeReader(r, &m)
+	return New().Parse(r, set)
+}
+
+// ConfigFileParser is a parser for the TOML file format. Flags and their values
+// are read from the key/value pairs defined in the config file.
+// Nested tables and keys are concatenated with a delimiter to derive the
+// relevant flag name.
+type ConfigFileParser struct {
+	delimiter string
+}
+
+// New constructs and configures a ConfigFileParser using the provided options.
+func New(opts ...Option) (c ConfigFileParser) {
+	c.delimiter = "."
+	for _, opt := range opts {
+		opt(&c)
+	}
+	return c
+}
+
+// Parse parses the provided io.Reader as a TOML file and uses the provided set function
+// to set flag names derived from the tables names and their key/value pairs.
+func (c ConfigFileParser) Parse(r io.Reader, set func(name, value string) error) error {
+	tree, err := toml.LoadReader(r)
 	if err != nil {
 		return ParseError{Inner: err}
 	}
-	for key, val := range m {
-		values, err := valsToStrs(val)
-		if err != nil {
-			return ParseError{Inner: err}
+
+	return parseTree(tree, "", c.delimiter, set)
+}
+
+// Option is a function which changes the behavior of the TOML config file parser.
+type Option func(*ConfigFileParser)
+
+// WithTableDelimiter is an option which configures a delimiter
+// used to prefix table names onto keys when constructing
+// their associated flag name.
+// The default delimiter is "."
+//
+// For example, given the following TOML
+//
+//     [section.subsection]
+//     value = 10
+//
+// Parse will match to a flag with the name `-section.subsection.value` by default.
+// If the delimiter is "-", Parse will match to `-section-subsection-value` instead.
+func WithTableDelimiter(d string) Option {
+	return func(c *ConfigFileParser) {
+		c.delimiter = d
+	}
+}
+
+func parseTree(tree *toml.Tree, parent, delimiter string, set func(name, value string) error) error {
+	for _, key := range tree.Keys() {
+		name := key
+		if parent != "" {
+			name = parent + delimiter + key
 		}
-		for _, value := range values {
-			if err = set(key, value); err != nil {
+		switch t := tree.Get(key).(type) {
+		case *toml.Tree:
+			if err := parseTree(t, name, delimiter, set); err != nil {
 				return err
 			}
+		case interface{}:
+			values, err := valsToStrs(t)
+			if err != nil {
+				return ParseError{Inner: err}
+			}
+			for _, value := range values {
+				if err = set(name, value); err != nil {
+					return err
+				}
+			}
 		}
 	}
 	return nil

fftoml/fftoml_test.go

@@ -1,6 +1,8 @@
 package fftoml_test
 
 import (
+	"flag"
+	"reflect"
 	"testing"
 	"time"
 
@@ -23,12 +25,19 @@ func TestParser(t *testing.T) {
 		{
 			name: "basic KV pairs",
 			file: "testdata/basic.toml",
-			want: fftest.Vars{S: "s", I: 10, F: 3.14e10, B: true, D: 5 * time.Second, X: []string{"1", "a", "👍"}},
+			want: fftest.Vars{
+				S: "s",
+				I: 10,
+				F: 3.14e10,
+				B: true,
+				D: 5 * time.Second,
+				X: []string{"1", "a", "👍"},
+			},
 		},
 		{
 			name: "bad TOML file",
 			file: "testdata/bad.toml",
-			want: fftest.Vars{WantParseErrorString: "bare keys cannot contain '{'"},
+			want: fftest.Vars{WantParseErrorString: "keys cannot contain { character"},
 		},
 	} {
 		t.Run(testcase.name, func(t *testing.T) {
@@ -43,3 +52,63 @@ func TestParser(t *testing.T) {
 		})
 	}
 }
+
+func TestParser_WithTables(t *testing.T) {
+	type fields struct {
+		String  string
+		Float   float64
+		Strings fftest.StringSlice
+	}
+
+	expected := fields{
+		String:  "a string",
+		Float:   1.23,
+		Strings: fftest.StringSlice{"one", "two", "three"},
+	}
+
+	for _, testcase := range []struct {
+		name string
+		opts []fftoml.Option
+		// expectations
+		stringKey  string
+		floatKey   string
+		stringsKey string
+	}{
+		{
+			name:       "defaults",
+			stringKey:  "string.key",
+			floatKey:   "float.nested.key",
+			stringsKey: "strings.nested.key",
+		},
+		{
+			name:       "defaults",
+			opts:       []fftoml.Option{fftoml.WithTableDelimiter("-")},
+			stringKey:  "string-key",
+			floatKey:   "float-nested-key",
+			stringsKey: "strings-nested-key",
+		},
+	} {
+		t.Run(testcase.name, func(t *testing.T) {
+			var (
+				found fields
+				fs    = flag.NewFlagSet("fftest", flag.ContinueOnError)
+			)
+
+			fs.StringVar(&found.String, testcase.stringKey, "", "string")
+			fs.Float64Var(&found.Float, testcase.floatKey, 0, "float64")
+			fs.Var(&found.Strings, testcase.stringsKey, "string slice")
+
+			if err := ff.Parse(fs, []string{},
+				ff.WithConfigFile("testdata/table.toml"),
+				ff.WithConfigFileParser(fftoml.New(testcase.opts...).Parse),
+			); err != nil {
+				t.Fatal(err)
+			}
+
+			if !reflect.DeepEqual(expected, found) {
+				t.Errorf(`expected %v, to be %v`, found, expected)
+			}
+		})
+	}
+
+}

fftoml/testdata/table.toml

@@ -0,0 +1,7 @@
+[string]
+key = "a string"
+[float]
+[float.nested]
+key = 1.23
+[strings.nested]
+key = ["one", "two", "three"]

go.mod

@@ -3,8 +3,8 @@ module github.com/peterbourgon/ff
 go 1.13
 
 require (
-	github.com/BurntSushi/toml v0.3.1
 	github.com/mitchellh/go-wordwrap v1.0.0
+	github.com/pelletier/go-toml v1.6.0
 	golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7
-	gopkg.in/yaml.v2 v2.2.2
+	gopkg.in/yaml.v2 v2.2.4
 )

go.sum

@@ -1,10 +1,14 @@
 github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/mitchellh/go-wordwrap v1.0.0 h1:6GlHJ/LTGMrIJbwgdqdl2eEH8o+Exx/0m8ir9Gns0u4=
 github.com/mitchellh/go-wordwrap v1.0.0/go.mod h1:ZXFpozHsX6DPmq2I0TCekCxypsnAUbP2oI0UX1GXzOo=
+github.com/pelletier/go-toml v1.6.0 h1:aetoXYr0Tv7xRU/V4B4IZJ2QcbtMUFoNb3ORp7TzIK4=
+github.com/pelletier/go-toml v1.6.0/go.mod h1:5N711Q9dKgbdkxHL+MEfF31hpT7l0S0s/t2kKREewys=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7 h1:9zdDQZ7Thm29KFXgAX/+yaf3eVbP7djjWp/dXAppNCc=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
-gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.2.4 h1:/eiJrUcujPVeJ3xlSWaiNi3uSVmDGBK1pDHUHAnao1I=
+gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=