Merge pull request #66 from heetch/origin/041-go2avro

cmd/go2avro: new command

cmd/go2avro/main.go

@@ -0,0 +1,178 @@
+// The go2avro command generates Avro schemas for Go types.
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	stdflag "flag"
+	"fmt"
+	"go/format"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"text/template"
+)
+
+var flag = stdflag.NewFlagSet("", stdflag.ContinueOnError)
+
+func main() {
+	os.Exit(main1())
+}
+
+func main1() int {
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, `usage: go2avro [package.]type
+
+This command prints the Avro schema for a given Go type on the
+standard output.
+
+If the package isn't specified, the current directory is used.
+Current implementation restrictions mean that schemas can only
+be generated for exported Go types.
+
+For example:
+
+	go2avro foo.com/bar/somepkg.Foo
+`[1:])
+	}
+	if flag.Parse(os.Args[1:]) != nil {
+		return 2
+	}
+	if len(flag.Args()) != 1 {
+		flag.Usage()
+		return 2
+	}
+	if err := main2(); err != nil {
+		fmt.Fprintf(os.Stderr, "go2avro: %v\n", err)
+		return 1
+	}
+	return 0
+}
+
+func main2() error {
+	pkgType := flag.Arg(0)
+	var p tmplParams
+	if i := strings.LastIndex(pkgType, "."); i < 0 {
+		var err error
+		p.Package, err = currentPkg()
+		if err != nil {
+			return fmt.Errorf("cannot get current package: %v", err)
+		}
+		p.Type = pkgType
+	} else {
+		p.Package = pkgType[0:i]
+		p.Type = pkgType[i+1:]
+	}
+	var codeBuf bytes.Buffer
+	if err := tmpl.Execute(&codeBuf, p); err != nil {
+		return fmt.Errorf("cannot execute template: %v", err)
+	}
+	code, err := format.Source(codeBuf.Bytes())
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "invalid temporary Go code:\n-------\n%s-----\n", codeBuf.String())
+		return fmt.Errorf("invalid template code: %v", err)
+	}
+	// Build the binary before executing the code so we can
+	// distinguish between build errors and Avro errors.
+	exe, err := buildGo(code)
+	if err != nil {
+		return err
+	}
+	defer os.Remove(exe)
+
+	var outBuf bytes.Buffer
+	var errBuf bytes.Buffer
+	cmd := exec.Command(exe)
+	cmd.Stdout = &outBuf
+	cmd.Stderr = &errBuf
+	if err := cmd.Run(); err != nil {
+		if errBuf.Len() > 0 {
+			return fmt.Errorf("cannot get Avro type: %s", strings.TrimSpace(errBuf.String()))
+		}
+		return err
+	}
+	var indentJSON bytes.Buffer
+	if err := json.Indent(&indentJSON, outBuf.Bytes(), "", "    "); err != nil {
+		return fmt.Errorf("cannot indent JSON: %v", err)
+	}
+	fmt.Printf("%s", indentJSON.String())
+	return nil
+}
+
+func buildGo(code []byte) (string, error) {
+	// Create the Go file in the current directory so that we
+	// take advantage of the current Go module.
+	// TODO avoid the side-effect of adding the avro import, somehow.
+	tmpFile, err := ioutil.TempFile(".", "go2avro_temp_*.go")
+	if err != nil {
+		return "", fmt.Errorf("cannot generate temp file: %v", err)
+	}
+	defer os.Remove(tmpFile.Name())
+	_, err = tmpFile.Write(code)
+	tmpFile.Close()
+	if err != nil {
+		return "", fmt.Errorf("cannot write %q: %v", tmpFile.Name(), err)
+	}
+	tmpBinary, err := ioutil.TempFile(".", "go2avro_temp_bin")
+	if err != nil {
+		return "", fmt.Errorf("cannot generate temp binary file: %v", err)
+	}
+	tmpBinary.Close()
+
+	var errBuf bytes.Buffer
+	cmd := exec.Command("go", "build", "-o", tmpBinary.Name(), tmpFile.Name())
+	cmd.Stderr = &errBuf
+	if err := cmd.Run(); err != nil {
+		defer os.Remove(tmpBinary.Name())
+		return "", fmt.Errorf("cannot build: %v", errBuf.String())
+	}
+	// Use explicit "./" prefix because . isn't always in $PATH.
+	return "." + string(filepath.Separator) + tmpBinary.Name(), nil
+}
+
+func currentPkg() (string, error) {
+	var buf bytes.Buffer
+	c := exec.Command("go", "list")
+	c.Stderr = os.Stderr
+	c.Stdout = &buf
+	if err := c.Run(); err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(buf.String()), nil
+}
+
+type tmplParams struct {
+	Package string
+	Type    string
+}
+
+var tmpl = template.Must(template.New("").Parse(`
+// Code generated by avrogen. DO NOT EDIT.
+
+// This should be treated as a temporary file. Remove it if you find it.
+
+// +build ignore
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/heetch/avro"
+
+	pkg {{printf "%q" .Package}}
+)
+
+func main() {
+	var x pkg.{{.Type}}
+	t, err := avro.TypeOf(x)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "cannot get type: %v\n", err)
+		os.Exit(1)
+	}
+	fmt.Println(t)
+}
+`))

cmd/go2avro/script_test.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"os"
+	"testing"
+
+	"github.com/rogpeppe/go-internal/gotooltest"
+	"github.com/rogpeppe/go-internal/testscript"
+)
+
+func TestMain(m *testing.M) {
+	os.Exit(testscript.RunMain(m, map[string]func() int{
+		"go2avro": main1,
+	}))
+}
+
+func TestFoo(t *testing.T) {
+	p := testscript.Params{
+		Dir: "testdata",
+	}
+	if err := gotooltest.Setup(&p); err != nil {
+		t.Fatal(err)
+	}
+	testscript.Run(t, p)
+}

cmd/go2avro/testdata/badtype.txt

@@ -0,0 +1,16 @@
+! go2avro T
+stderr 'go2avro: cannot get Avro type: cannot get type: cannot make Avro schema for Go type chan int'
+
+-- bar.go --
+package bar
+
+type T struct {
+	X chan int
+}
+
+-- go.mod --
+module example.com/foo/bar
+
+go 1.14
+
+require github.com/heetch/avro v0.0.0-20200318154341-de261c0e4b7f // indirect

cmd/go2avro/testdata/simple.txt

@@ -0,0 +1,31 @@
+go2avro T
+cmp stdout expect-stdout
+
+go2avro example.com/foo/bar.T
+cmp stdout expect-stdout
+
+-- expect-stdout --
+{
+    "fields": [
+        {
+            "default": 0,
+            "name": "X",
+            "type": "long"
+        }
+    ],
+    "name": "T",
+    "type": "record"
+}
+-- bar.go --
+package bar
+
+type T struct {
+	X int
+}
+
+-- go.mod --
+module example.com/foo/bar
+
+go 1.14
+
+require github.com/heetch/avro v0.0.0-20200318154341-de261c0e4b7f // indirect

cmd/go2avro/testdata/unknowntype.txt

@@ -0,0 +1,12 @@
+! go2avro Foo
+stderr 'undefined: bar.Foo'
+
+-- bar.go --
+package bar
+
+-- go.mod --
+module example.com/foo/bar
+
+go 1.14
+
+require github.com/heetch/avro v0.0.0-20200318154341-de261c0e4b7f // indirect

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/frankban/quicktest v1.7.2
 	github.com/kr/pretty v0.1.0
 	github.com/linkedin/goavro/v2 v2.9.7
+	github.com/rogpeppe/go-internal v1.5.2
 	github.com/rogpeppe/gogen-avro/v7 v7.2.1
 	gopkg.in/retry.v1 v1.0.3
 )

go.sum

@@ -20,8 +20,14 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/rogpeppe/clock v0.0.0-20190514195947-2896927a307a h1:3QH7VyOaaiUHNrA9Se4YQIRkDTCw1EJls9xTUCaCeRM=
 github.com/rogpeppe/clock v0.0.0-20190514195947-2896927a307a/go.mod h1:4r5QyqhjIWCcK8DO4KMclc5Iknq5qVBAlbYYzAbUScQ=
+github.com/rogpeppe/go-internal v1.5.2 h1:qLvObTrvO/XRCqmkKxUlOBc48bI3efyDuAZe25QiF0w=
+github.com/rogpeppe/go-internal v1.5.2/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTEfhy4qGm1nDQc=
 github.com/rogpeppe/gogen-avro/v7 v7.2.1 h1:laf1RaIs397v8rAhLGtpznjOIuXYQDJ/7ij0dAss4Gg=
 github.com/rogpeppe/gogen-avro/v7 v7.2.1/go.mod h1:awhtQwpFg18PdUpdnOFr0ceVLYAn/oDCa/HE1hdbk50=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
+gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/errgo.v2 v2.1.0 h1:0vLT13EuvQ0hNvakwLuFZ/jYrLp5F3kcWHXdRggjCE8=
+gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/retry.v1 v1.0.3 h1:a9CArYczAVv6Qs6VGoLMio99GEs7kY9UzSF9+LD+iGs=
 gopkg.in/retry.v1 v1.0.3/go.mod h1:FJkXmWiMaAo7xB+xhvDF59zhfjDWyzmyAxiT4dB688g=