Add skeleton of a config

Took way longer than it should had because I was researching exisiting
options.

As it turns out, nothing nice exists that would handle:
 - Multiple overridiable config files
 - Defaults provided in a struct
 - Output in a struct

License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>

.golangci.yml

@@ -18,6 +18,7 @@ linters:
 issues:
   exclude:
     - "func name will be used as test\\.Test.* by other packages, and that stutters; consider calling this"
+    - "Potential file inclusion via variable"
 
   exclude-use-default: false
   exclude-rules:

go.mod

@@ -3,6 +3,9 @@ module github.com/filecoin-project/go-lotus
 go 1.12
 
 require (
+	github.com/BurntSushi/toml v0.3.1
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/golang/protobuf v1.3.1 // indirect
 	github.com/ipfs/go-datastore v0.0.5
 	github.com/ipfs/go-ipfs-routing v0.1.0
 	github.com/ipfs/go-log v0.0.2-0.20190703113630-0c3cfb1eccc4
@@ -25,9 +28,11 @@ require (
 	github.com/libp2p/go-maddr-filter v0.0.4
 	github.com/multiformats/go-multiaddr v0.0.4
 	github.com/multiformats/go-multihash v0.0.5
+	github.com/stretchr/testify v1.3.0
 	github.com/whyrusleeping/multiaddr-filter v0.0.0-20160516205228-e903e4adabd7
 	go.uber.org/dig v1.7.0 // indirect
 	go.uber.org/fx v1.9.0
 	go.uber.org/goleak v0.10.0 // indirect
 	gopkg.in/urfave/cli.v2 v2.0.0-20180128182452-d3ae77c26ac8
+	gopkg.in/yaml.v2 v2.2.2 // indirect
 )

go.sum

@@ -1,5 +1,6 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
 github.com/AndreasBriese/bbloom v0.0.0-20180913140656-343706a395b7/go.mod h1:bOvUY6CB00SOBii9/FifXqc0awNKxLFCL/+pkDPuyl8=
+github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
 github.com/Kubuxu/go-os-helper v0.0.1/go.mod h1:N8B+I7vPCT80IcP58r50u4+gEEcsZETFUpAzWW2ep1Y=
 github.com/aead/siphash v1.0.1/go.mod h1:Nywa3cDsYNNK3gaciGTWPwHt0wlpNV15vwmswBAUSII=
@@ -22,6 +23,8 @@ github.com/coreos/go-semver v0.3.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3Ee
 github.com/davecgh/go-spew v0.0.0-20171005155431-ecdeabc65495/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+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/davidlazar/go-crypto v0.0.0-20170701192655-dcfb0a7ac018 h1:6xT9KW8zLC5IlbaIF5Q7JNieBoACT7iW0YTxQHR0in0=
 github.com/davidlazar/go-crypto v0.0.0-20170701192655-dcfb0a7ac018/go.mod h1:rQYf4tfk5sSwFsnDg3qYaBxSjsD9S8+59vW0dKUgme4=
 github.com/dgraph-io/badger v1.5.5-0.20190226225317-8115aed38f8f/go.mod h1:VZxzAIRPHRVNRKRo6AXrX9BJegn6il06VMTZVJYCIjQ=
@@ -40,6 +43,8 @@ github.com/golang/mock v1.2.0/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfb
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.0 h1:kbxbvI4Un1LUWKxufD+BiE6AEExYYgkQLQmLFqA1LFk=
 github.com/golang/protobuf v1.3.0/go.mod h1:Qd/q+1AKNOZr9uGQzbzCmRO6sUih6GTPZv6a1/R87v0=
+github.com/golang/protobuf v1.3.1 h1:YF8+flBXS5eO826T4nzqPrxfhQThhXl0YzfuUPu4SBg=
+github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/snappy v0.0.0-20180518054509-2e65f85255db/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/google/go-cmp v0.2.0 h1:+dTQ8DZQJz0Mb/HjFlkptS1FeQ4cWSnN941F8aEG4SQ=
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
@@ -364,4 +369,6 @@ gopkg.in/urfave/cli.v2 v2.0.0-20180128182452-d3ae77c26ac8 h1:Ggy3mWN4l3PUFPfSG0Y
 gopkg.in/urfave/cli.v2 v2.0.0-20180128182452-d3ae77c26ac8/go.mod h1:cKXr3E0k4aosgycml1b5z33BVV6hai1Kh7uDgFOkbcs=
 gopkg.in/yaml.v2 v2.2.1 h1:mUhvW9EsL+naU5Q3cakzfE91YhliOondGd6ZrsDBHQE=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

node/config/def.go

@@ -0,0 +1,38 @@
+package config
+
+import "time"
+
+// Root is starting point of the config
+type Root struct {
+	API API
+}
+
+// API contains configs for API endpoint
+type API struct {
+	ListenAddress string
+	Timeout       Duration
+}
+
+// Default returns the default config
+func Default() *Root {
+	def := Root{
+		API: API{
+			ListenAddress: "/ip6/::1/tcp/1234/http",
+			Timeout:       Duration(30 * time.Second),
+		},
+	}
+	return &def
+}
+
+// Duration is a wrapper type for time.Duration for decoding it from TOML
+type Duration time.Duration
+
+// UnmarshalText implements interface for TOML decoding
+func (dur *Duration) UnmarshalText(text []byte) error {
+	d, err := time.ParseDuration(string(text))
+	if err != nil {
+		return err
+	}
+	*dur = Duration(d)
+	return err
+}

node/config/load.go

@@ -0,0 +1,34 @@
+package config
+
+import (
+	"io"
+	"os"
+
+	"github.com/BurntSushi/toml"
+)
+
+// FromFile loads config from a specified file overriding defaults specified in
+// the source code. If file does not exist or is empty defaults are asummed.
+func FromFile(path string) (*Root, error) {
+	file, err := os.Open(path)
+	switch {
+	case os.IsNotExist(err):
+		return Default(), nil
+	case err != nil:
+		return nil, err
+	}
+
+	defer file.Close() //nolint:errcheck // The file is RO
+	return FromReader(file)
+}
+
+// FromReader loads config from a reader instance.
+func FromReader(reader io.Reader) (*Root, error) {
+	cfg := Default()
+	_, err := toml.DecodeReader(reader, cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	return cfg, nil
+}

node/config/load_test.go

@@ -0,0 +1,63 @@
+package config
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDecodeNothing(t *testing.T) {
+	assert := assert.New(t)
+
+	{
+		cfg, err := FromFile(os.DevNull)
+		assert.Nil(err, "error should be nil")
+		assert.Equal(Default(), cfg,
+			"config from empty file should be the same as default")
+	}
+
+	{
+		cfg, err := FromFile("./does-not-exist.toml")
+		assert.Nil(err, "error should be nil")
+		assert.Equal(Default(), cfg,
+			"config from not exisiting file should be the same as default")
+	}
+}
+
+func TestParitalConfig(t *testing.T) {
+	assert := assert.New(t)
+	cfgString := ` 
+		[API]
+		Timeout = "10s"
+		`
+	expected := Default()
+	expected.API.Timeout = Duration(10 * time.Second)
+
+	{
+		cfg, err := FromReader(bytes.NewReader([]byte(cfgString)))
+		assert.NoError(err, "error should be nil")
+		assert.Equal(expected, cfg,
+			"config from reader should contain changes")
+	}
+
+	{
+		f, err := ioutil.TempFile("", "config-*.toml")
+		fname := f.Name()
+
+		assert.NoError(err, "tmp file shold not error")
+		_, err = f.WriteString(cfgString)
+		assert.NoError(err, "writing to tmp file should not error")
+		err = f.Close()
+		assert.NoError(err, "closing tmp file should not error")
+		defer os.Remove(fname) //nolint:errcheck
+
+		cfg, err := FromFile(fname)
+		assert.Nil(err, "error should be nil")
+		assert.Equal(expected, cfg,
+			"config from reader should contain changes")
+	}
+}