compiler: add ability to generate .abi.json file

A part of integration with NEO Blockchain Toolkit (see #902). To be
able to deploy smart-contract compiled with neo-go compiler via NEO
Express, we have to generate additional .abi.json file. This file
contains the following information:
 - hash of the compiled contract
 - smart-contract metadata (title, description, version, author,
email, has-storage, has-dynamic-invoke, is-payable)
 - smart-contract entry point
 - functions
 - events

However, this .abi.json file is slightly different from the one,
described in manifest.go, so we have to add auxilaury stractures for
json marshalling. The .abi.json format used by NEO-Express is described
[here](https://github.com/neo-project/neo-devpack-dotnet/blob/master/src/Neo.Compiler.MSIL/FuncExport.cs#L66).

cli/smartcontract/smart_contract.go

@@ -97,6 +97,14 @@ func NewCommands() []cli.Command {
 						Name:  "debug, d",
 						Usage: "Emit debug info in a separate file",
 					},
+					cli.StringFlag{
+						Name:  "abi, a",
+						Usage: "Emit application binary interface (.abi.json) file into separate file using configuration input file (*.yml)",
+					},
+					cli.StringFlag{
+						Name:  "config, c",
+						Usage: "Configuration input file (*.yml)",
+					},
 				},
 			},
 			{
@@ -349,11 +357,25 @@ func contractCompile(ctx *cli.Context) error {
 	if len(src) == 0 {
 		return cli.NewExitError(errNoInput, 1)
 	}
+	abi := ctx.String("abi")
+	confFile := ctx.String("config")
+	if len(abi) != 0 && len(confFile) == 0 {
+		return cli.NewExitError(errNoConfFile, 1)
+	}
 
 	o := &compiler.Options{
 		Outfile: ctx.String("out"),
 
 		DebugInfo: ctx.String("debug"),
+		ABIInfo:   abi,
+	}
+
+	if len(confFile) != 0 {
+		conf, err := parseContractConfig(confFile)
+		if err != nil {
+			return err
+		}
+		o.ContractDetails = &conf.Contract
 	}
 
 	result, err := compiler.CompileAndSave(src, o)
@@ -614,15 +636,9 @@ func contractDeploy(ctx *cli.Context) error {
 	if err != nil {
 		return cli.NewExitError(err, 1)
 	}
-	confBytes, err := ioutil.ReadFile(confFile)
+	conf, err := parseContractConfig(confFile)
 	if err != nil {
-		return cli.NewExitError(err, 1)
-	}
-
-	conf := ProjectConfig{}
-	err = yaml.Unmarshal(confBytes, &conf)
-	if err != nil {
-		return cli.NewExitError(fmt.Errorf("bad config: %v", err), 1)
+		return err
 	}
 
 	c, err := client.New(context.TODO(), endpoint, client.Options{})
@@ -644,3 +660,17 @@ func contractDeploy(ctx *cli.Context) error {
 	fmt.Printf("Sent deployment transaction %s for contract %s\n", txHash.StringLE(), hash.Hash160(avm).StringLE())
 	return nil
 }
+
+func parseContractConfig(confFile string) (ProjectConfig, error) {
+	conf := ProjectConfig{}
+	confBytes, err := ioutil.ReadFile(confFile)
+	if err != nil {
+		return conf, cli.NewExitError(err, 1)
+	}
+
+	err = yaml.Unmarshal(confBytes, &conf)
+	if err != nil {
+		return conf, cli.NewExitError(fmt.Errorf("bad config: %v", err), 1)
+	}
+	return conf, nil
+}

pkg/compiler/compiler.go

@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"strings"
 
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
 	"golang.org/x/tools/go/loader"
 )
 
@@ -26,6 +27,12 @@ type Options struct {
 
 	// The name of the output for debug info.
 	DebugInfo string
+
+	// The name of the output for application binary interface info.
+	ABIInfo string
+
+	// Contract metadata.
+	ContractDetails *smartcontract.ContractDetails
 }
 
 type buildInfo struct {
@@ -105,5 +112,16 @@ func CompileAndSave(src string, o *Options) ([]byte, error) {
 	if err != nil {
 		return b, err
 	}
-	return b, ioutil.WriteFile(o.DebugInfo, data, os.ModePerm)
+	if err := ioutil.WriteFile(o.DebugInfo, data, os.ModePerm); err != nil {
+		return b, err
+	}
+	if o.ABIInfo == "" {
+		return b, err
+	}
+	abi := di.convertToABI(b, o.ContractDetails)
+	abiData, err := json.Marshal(abi)
+	if err != nil {
+		return b, err
+	}
+	return b, ioutil.WriteFile(o.ABIInfo, abiData, os.ModePerm)
 }

pkg/compiler/debug.go

@@ -8,6 +8,10 @@ import (
 	"go/types"
 	"strconv"
 	"strings"
+
+	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/util"
 )
 
 // DebugInfo represents smart-contract debug information.
@@ -72,8 +76,42 @@ type DebugRange struct {
 
 // DebugParam represents variables's name and type.
 type DebugParam struct {
-	Name string
-	Type string
+	Name string `json:"name"`
+	Type string `json:"type"`
+}
+
+// ABI represents ABI contract info in compatible with NEO Blockchain Toolkit format
+type ABI struct {
+	Hash       util.Uint160 `json:"hash"`
+	Metadata   Metadata     `json:"metadata"`
+	EntryPoint string       `json:"entrypoint"`
+	Functions  []Method     `json:"functions"`
+	Events     []Event      `json:"events"`
+}
+
+// Metadata represents ABI contract metadata
+type Metadata struct {
+	Author               string `json:"author"`
+	Email                string `json:"email"`
+	Version              string `json:"version"`
+	Title                string `json:"title"`
+	Description          string `json:"description"`
+	HasStorage           bool   `json:"has-storage"`
+	HasDynamicInvocation bool   `json:"has-dynamic-invoke"`
+	IsPayable            bool   `json:"is-payable"`
+}
+
+// Method represents ABI method's metadata.
+type Method struct {
+	Name       string       `json:"name"`
+	Parameters []DebugParam `json:"parameters"`
+	ReturnType string       `json:"returntype"`
+}
+
+// Event represents ABI event's metadata.
+type Event struct {
+	Name       string       `json:"name"`
+	Parameters []DebugParam `json:"parameters"`
 }
 
 func (c *codegen) saveSequencePoint(n ast.Node) {
@@ -260,3 +298,40 @@ func parsePairJSON(data []byte, sep string) (string, string, error) {
 	}
 	return ss[0], ss[1], nil
 }
+
+func (di *DebugInfo) convertToABI(contract []byte, cd *smartcontract.ContractDetails) ABI {
+	methods := make([]Method, 0)
+	for _, method := range di.Methods {
+		if method.Name.Name == di.EntryPoint {
+			methods = append(methods, Method{
+				Name:       method.Name.Name,
+				Parameters: method.Parameters,
+				ReturnType: cd.ReturnType.String(),
+			})
+			break
+		}
+	}
+	events := make([]Event, len(di.Events))
+	for i, event := range di.Events {
+		events[i] = Event{
+			Name:       event.Name,
+			Parameters: event.Parameters,
+		}
+	}
+	return ABI{
+		Hash: hash.Hash160(contract),
+		Metadata: Metadata{
+			Author:               cd.Author,
+			Email:                cd.Email,
+			Version:              cd.Version,
+			Title:                cd.ProjectName,
+			Description:          cd.Description,
+			HasStorage:           cd.HasStorage,
+			HasDynamicInvocation: cd.HasDynamicInvocation,
+			IsPayable:            cd.IsPayable,
+		},
+		EntryPoint: di.EntryPoint,
+		Functions:  methods,
+		Events:     events,
+	}
+}

pkg/compiler/debug_test.go

@@ -3,7 +3,9 @@ package compiler
 import (
 	"testing"
 
+	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
 	"github.com/nspcc-dev/neo-go/pkg/internal/testserdes"
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
 	"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -113,6 +115,56 @@ func methodStruct() struct{} { return struct{}{} }
 		require.True(t, int(index) < len(buf))
 		require.EqualValues(t, opcode.RET, buf[index])
 	}
+
+	t.Run("convert to ABI", func(t *testing.T) {
+		author := "Joe"
+		email := "Joe@ex.com"
+		version := "1.0"
+		title := "MyProj"
+		description := "Description"
+		actual := d.convertToABI(buf, &smartcontract.ContractDetails{
+			Author:               author,
+			Email:                email,
+			Version:              version,
+			ProjectName:          title,
+			Description:          description,
+			HasStorage:           true,
+			HasDynamicInvocation: false,
+			IsPayable:            false,
+			ReturnType:           smartcontract.BoolType,
+			Parameters: []smartcontract.ParamType{
+				smartcontract.StringType,
+			},
+		})
+		expected := ABI{
+			Hash: hash.Hash160(buf),
+			Metadata: Metadata{
+				Author:               author,
+				Email:                email,
+				Version:              version,
+				Title:                title,
+				Description:          description,
+				HasStorage:           true,
+				HasDynamicInvocation: false,
+				IsPayable:            false,
+			},
+			EntryPoint: mainIdent,
+			Functions: []Method{
+				{
+					Name: mainIdent,
+					Parameters: []DebugParam{
+						{
+							Name: "op",
+							Type: "String",
+						},
+					},
+					ReturnType: "Boolean",
+				},
+			},
+			Events: []Event{},
+		}
+		assert.Equal(t, expected, actual)
+	})
 }
 
 func TestSequencePoints(t *testing.T) {