filter mageimport files (#281)

When calling mage import, we weren't prefiltering the list of go
files, so we'd get files with build tags and test files and such.
What we want is just the normal go files for building the library.
Using go list returns us that, so use that.

parse/parse.go

@@ -230,6 +230,7 @@ func getNamedImports(gocmd string, pkgs map[string]string) ([]*Import, error) {
 	return imports, nil
 }
 
+// getImport returns the metadata about a package that has been mage:import'ed.
 func getImport(gocmd, importpath, alias string) (*Import, error) {
 	out, err := internal.OutputDebug(gocmd, "list", "-f", "{{.Dir}}||{{.Name}}", importpath)
 	if err != nil {
@@ -241,7 +242,17 @@ func getImport(gocmd, importpath, alias string) (*Import, error) {
 	}
 	dir, name := parts[0], parts[1]
 	debug.Printf("parsing imported package %q from dir %q", importpath, dir)
-	info, err := Package(dir, nil)
+
+	// we use go list to get the list of files, since go/parser doesn't differentiate between
+	// go files with build tags etc, and go list does. This prevents weird problems if you
+	// have more than one package in a folder because of build tags.
+	out, err = internal.OutputDebug(gocmd, "list", "-f", `{{join .GoFiles "||"}}`, importpath)
+	if err != nil {
+		return nil, err
+	}
+	files := strings.Split(out, "||")
+
+	info, err := Package(dir, files)
 	if err != nil {
 		return nil, err
 	}
@@ -253,6 +264,7 @@ func getImport(gocmd, importpath, alias string) (*Import, error) {
 	return &Import{Alias: alias, Name: name, Path: importpath, Info: *info}, nil
 }
 
+// Import represents the data about a mage:import package
 type Import struct {
 	Alias      string
 	Name       string
@@ -653,7 +665,7 @@ func getFunction(exp ast.Expr, pi *PkgInfo) (*Function, error) {
 	return nil, fmt.Errorf("unknown package for function %q", exp)
 }
 
-// getPackage returns the non-test package at the given path.
+// getPackage returns the importable package at the given path.
 func getPackage(path string, files []string, fset *token.FileSet) (*ast.Package, error) {
 	var filter func(f os.FileInfo) bool
 	if len(files) > 0 {
@@ -672,12 +684,21 @@ func getPackage(path string, files []string, fset *token.FileSet) (*ast.Package,
 		return nil, fmt.Errorf("failed to parse directory: %v", err)
 	}
 
-	for name, pkg := range pkgs {
-		if !strings.HasSuffix(name, "_test") {
-			return pkg, nil
+	switch len(pkgs) {
+	case 1:
+		var pkg *ast.Package
+		for _, pkg = range pkgs {
+		}
+		return pkg, nil
+	case 0:
+		return nil, fmt.Errorf("no importable packages found in %s", path)
+	default:
+		var names []string
+		for name := range pkgs {
+			names = append(names, name)
 		}
+		return nil, fmt.Errorf("multiple packages found in %s: %v", path, strings.Join(names, ", "))
 	}
-	return nil, fmt.Errorf("no non-test packages found in %s", path)
 }
 
 func hasContextParam(ft *ast.FuncType) bool {

parse/parse_test.go

@@ -1,10 +1,18 @@
 package parse
 
 import (
+	"log"
+	"os"
 	"reflect"
 	"testing"
+
+	"github.com/magefile/mage/internal"
 )
 
+func init() {
+	internal.SetDebug(log.New(os.Stdout, "", 0))
+}
+
 func TestParse(t *testing.T) {
 	info, err := PrimaryPackage("go", "./testdata", []string{"func.go", "command.go", "alias.go", "repeating_synopsis.go", "subcommands.go"})
 	if err != nil {
@@ -94,3 +102,13 @@ func TestParse(t *testing.T) {
 		}
 	}
 }
+
+func TestGetImportSelf(t *testing.T) {
+	imp, err := getImport("go", "github.com/magefile/mage/parse/testdata/importself", "")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if imp.Info.AstPkg.Name != "importself" {
+		t.Fatalf("expected package importself, got %v", imp.Info.AstPkg.Name)
+	}
+}

parse/testdata/importself/magefile.go

@@ -0,0 +1,14 @@
+//+build mage
+
+package main
+
+import (
+	"fmt"
+
+	// mage:import
+	_ "github.com/magefile/mage/parse/testdata/importself"
+)
+
+func Build(){
+	fmt.Println("built")
+}

parse/testdata/importself/targets.go

@@ -0,0 +1,7 @@
+package importself
+
+import "fmt"
+
+func Stuff() {
+	fmt.Println("stuff")
+}