Feat: Add local package support (#34)

The current version of gogetdoc can't work for a local package,
This means if your code is not put in GOPATH, then you can't get any
help with gogetdoc.

This commit changes the current behavior and adds a function named
`importLocalPackage` which can import local packages, when
`buildutil.ContainingPackage(...)` failed, `importLocalPackage` will
be called instead of return an error.

It also adds two test cases for test `Run` from outside of GOPATH.

Author: flw-cn

main.go

@@ -99,7 +99,10 @@ func Run(ctx *build.Context, filename string, offset int64) (*Doc, error) {
 	}
 	bp, err := buildutil.ContainingPackage(ctx, wd, filename)
 	if err != nil {
-		return nil, fmt.Errorf("gogetdoc: couldn't get package for %s: %s", filename, err.Error())
+		bp, err = importLocalPackage(wd, filename)
+		if err != nil {
+			return nil, fmt.Errorf("gogetdoc: couldn't get package for %s: %s", filename, err.Error())
+		}
 	}
 	var parseError error
 	conf := &loader.Config{
@@ -226,3 +229,20 @@ func sameFile(a, b string) bool {
 	}
 	return false
 }
+
+func importLocalPackage(wd string, filename string) (*build.Package, error) {
+	if !filepath.IsAbs(filename) {
+		filename = filepath.Clean(filepath.Join(wd, filename))
+	}
+
+	filename, err := filepath.Rel(wd, filename)
+	if err != nil {
+		return build.Import(".", wd, build.FindOnly)
+	}
+
+	path := filepath.Dir(filename)
+	if path != "." {
+		path = "./" + path
+	}
+	return build.Import(path, wd, build.FindOnly)
+}

main_test.go

@@ -1,6 +1,13 @@
 package main
 
-import "testing"
+import (
+	"go/build"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
 
 func TestParseValidPos(t *testing.T) {
 	fname, offset, err := parsePos("foo.go:#123")
@@ -37,3 +44,65 @@ func TestParseInvalidPos(t *testing.T) {
 		}
 	}
 }
+
+func TestRunOutsideGopath(t *testing.T) {
+	cleanup, err := makeTempWorkspace("hello.go")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if cleanup != nil {
+		defer cleanup()
+	}
+
+	tests := []struct {
+		Pos int64
+		Doc string
+	}{
+		{Pos: 23, Doc: "\tPackage fmt implements formatted I/O"},    // import "fmt"
+		{Pos: 48, Doc: "Println formats using the default formats"}, // call fmt.Println()
+	}
+
+	for _, test := range tests {
+		ctx := build.Default
+		doc, err := Run(&ctx, "hello.go", test.Pos)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !strings.HasPrefix(doc.Doc, test.Doc) {
+			t.Errorf("want '%s', got '%s'", test.Doc, doc.Doc)
+		}
+	}
+}
+
+func makeTempWorkspace(fileList ...string) (cleanup func(), err error) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return nil, err
+	}
+
+	tmpDir, err := ioutil.TempDir("", "gogetdoc-tmp")
+	if err != nil {
+		return nil, err
+	}
+
+	for _, file := range fileList {
+		err = copyFile(filepath.Join(tmpDir, file), filepath.FromSlash("./testdata/"+file))
+		if err != nil {
+			os.RemoveAll(tmpDir)
+			return nil, err
+		}
+	}
+
+	err = os.Chdir(tmpDir)
+	if err != nil {
+		os.RemoveAll(tmpDir)
+		return nil, err
+	}
+
+	cleanup = func() {
+		os.RemoveAll(tmpDir)
+		os.Chdir(cwd)
+	}
+	return cleanup, nil
+}

testdata/hello.go

@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("Hello, world!")
+}