Add backtraces to error output and + update starlark dependency

go.mod

@@ -9,5 +9,5 @@ require (
 	github.com/kelseyhightower/envconfig v1.4.0
 	github.com/sirupsen/logrus v1.4.2
 	github.com/stretchr/testify v1.3.0 // indirect
-	go.starlark.net v0.0.0-20190820173200-988906f77f65
+	go.starlark.net v0.0.0-20200306205701-8dd3e2ee1dd5
 )

go.sum

@@ -5,6 +5,9 @@ github.com/bazelbuild/bazel-gazelle v0.19.1 h1:TSCGVqpHStCj1MTszuDfZt6Z2Ca8ekq2o
 github.com/bazelbuild/bazel-gazelle v0.19.1/go.mod h1:rPwzNHUqEzngx1iVBfO/2X2npKaT3tqPqqHW6rVsn/A=
 github.com/bazelbuild/buildtools v0.0.0-20190731111112-f720930ceb60/go.mod h1:5JP0TXzWDHXv8qvxRC4InIazwdyDseBDbzESUMKk1yU=
 github.com/bazelbuild/rules_go v0.0.0-20190719190356-6dae44dc5cab/go.mod h1:MC23Dc/wkXEyk3Wpq6lCqz0ZAYOZDw2DR5y3N1q2i7M=
+github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
+github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
+github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
 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=
@@ -34,10 +37,14 @@ github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 go.starlark.net v0.0.0-20190820173200-988906f77f65 h1:0766L84ADcyJQKl+NsKSJC8JBEuer/2RxL37StWfsx4=
 go.starlark.net v0.0.0-20190820173200-988906f77f65/go.mod h1:c1/X6cHgvdXj6pUlmWKMkuqRnW4K8x2vwt6JAaaircg=
+go.starlark.net v0.0.0-20200306205701-8dd3e2ee1dd5 h1:+FNtrFTmVw0YZGpBGX56XDee331t6JAXeK2bcyhLOOc=
+go.starlark.net v0.0.0-20200306205701-8dd3e2ee1dd5/go.mod h1:nmDLcffg48OtT/PSW0Hg7FvpRQsQh5OSqIylirxKC7o=
 golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190122071731-054c452bb702/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190422165155-953cdadca894 h1:Cz4ceDQGXuKRnVBDTS23GTn/pU5OE2C0WrNTOYK1Uuc=
 golang.org/x/sys v0.0.0-20190422165155-953cdadca894/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20191002063906-3421d5a6bb1c h1:Vco5b+cuG5NNfORVxZy6bYZQ7rsigisU1WQFkvQ0L5E=
+golang.org/x/sys v0.0.0-20191002063906-3421d5a6bb1c/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/tools v0.0.0-20190122202912-9c309ee22fab/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

plugin/plugin.go

@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"context"
 	"errors"
+	"fmt"
 
 	"github.com/drone/drone-convert-starlark/plugin/starlark/repo"
 
@@ -77,7 +78,7 @@ func (p *plugin) Convert(ctx context.Context, req *converter.Request) (*drone.Co
 	}
 	globals, err := starlark.ExecFile(thread, req.Repo.Config, []byte(req.Config.Data), nil)
 	if err != nil {
-		return nil, err
+		return nil, prettyStarlarkError(err)
 	}
 
 	// find the main method in the starlark script and
@@ -97,7 +98,7 @@ func (p *plugin) Convert(ctx context.Context, req *converter.Request) (*drone.Co
 	args := createArgs(req.Repo, req.Build)
 	mainVal, err = starlark.Call(thread, main, args, nil)
 	if err != nil {
-		return nil, err
+		return nil, prettyStarlarkError(err)
 	}
 
 	buf := new(bytes.Buffer)
@@ -145,3 +146,12 @@ func (p *plugin) loadExtension(t *starlark.Thread, labelStr string) (starlark.St
 	logrus.Debugln("successfully loaded extension", labelStr)
 	return loaded, err
 }
+
+// prettyStarlarkError returns a suitable human readable error for a
+// starlark.Exec error or returns the error unmodified.
+func prettyStarlarkError(err error) error {
+	if err, ok := err.(*starlark.EvalError); ok {
+		return fmt.Errorf("starlark evaluation error:\n%s", err.Backtrace())
+	}
+	return err
+}

plugin/plugin_test.go

@@ -250,3 +250,55 @@ func TestPlugin_Load_Unknown_Repo(t *testing.T) {
 		t.Error("expected ErrNoSuchRepo")
 	}
 }
+
+// Test that the fail builtin fails the build
+func TestPlugin_Fail(t *testing.T) {
+	req := &converter.Request{
+		Build: drone.Build{
+			After: "3d21ec53a331a6f037a91c368710b99387d012c1",
+		},
+		Repo: drone.Repo{
+			Slug:   "octocat/hello-world",
+			Config: ".drone.yml",
+		},
+	}
+
+	plugin := New(newTestRegistry(t))
+
+	config, err := plugin.Convert(noContext, req)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	if config != nil {
+		t.Error("Want nil config when configuration is not starlark file")
+		return
+	}
+
+	before, err := ioutil.ReadFile("testdata/fail.star")
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	after, err := ioutil.ReadFile("testdata/fail.error")
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	req.Repo.Config = "fail.star"
+	req.Config.Data = string(before)
+	config, err = plugin.Convert(noContext, req)
+	if err == nil {
+		t.Error("expected error")
+		return
+	}
+	if config != nil {
+		t.Error("Want non-nil configuration")
+		return
+	}
+
+	if want, got := err.Error(), string(after); want != got {
+		t.Errorf("Want %q got %q", want, got)
+	}
+}

plugin/testdata/fail.error

@@ -0,0 +1,7 @@
+starlark evaluation error:
+Traceback (most recent call last):
+  fail.star:2:8: in main
+  fail.star:5:8: in fn1
+  fail.star:8:9: in fn2
+  <builtin>: in fail
+Error: fail: fail-message

plugin/testdata/fail.star

@@ -0,0 +1,8 @@
+def main(ctx):
+    fn1()
+
+def fn1():
+    fn2()
+
+def fn2():
+    fail("fail-message")