Add a Corpus type representing a place where packages live.

corpus.go

@@ -0,0 +1,53 @@
+package goref
+
+import (
+	"fmt"
+	"go/build"
+	"path/filepath"
+	"strings"
+)
+
+// A Corpus represents a prefix from which Go packages may be loaded.
+// Default corpora are $GOROOT/src and each of $GOPATH/src
+type Corpus string
+
+// NewCorpus creates a new Corpus.
+func NewCorpus(basepath string) (Corpus, error) {
+	if !filepath.IsAbs(basepath) {
+		return Corpus(""), fmt.Errorf("Corpus %s has a relative basepath", basepath)
+	}
+	return Corpus(basepath), nil
+}
+
+// Contains returns whether the provided filepath exists under this
+// Corpus.
+func (c Corpus) Contains(fpath string) bool {
+	rel, err := filepath.Rel(string(c), fpath)
+	if err != nil {
+		return false
+	}
+	return !strings.HasPrefix(rel, "../") && rel != ".."
+}
+
+// Rel returns the relative path of a file within a Corpus.
+// If the string does not belong to the corpus, it returns fpath.
+func (c Corpus) Rel(fpath string) string {
+	if !c.Contains(fpath) {
+		return fpath
+	}
+	rel, err := filepath.Rel(string(c), fpath)
+	if err != nil {
+		return fpath
+	}
+	return rel
+}
+
+// Returns the set of default corpora based on GOROOT and GOPATH.
+func DefaultCorpora() []Corpus {
+	srcdirs := build.Default.SrcDirs()
+	corpora := make([]Corpus, len(srcdirs))
+	for n, s := range srcdirs {
+		corpora[n] = Corpus(s)
+	}
+	return corpora
+}

corpus_test.go

@@ -0,0 +1,32 @@
+package goref_test
+
+import (
+	"testing"
+
+	"github.com/korfuri/goref"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestContains(t *testing.T) {
+	assert.True(t, goref.Corpus("/a/b/c").Contains("/a/b/c/d"))
+	assert.True(t, goref.Corpus("/a/b/c/d").Contains("/a/b/c/d"))
+	assert.True(t, goref.Corpus("/").Contains("/a/b/c/d"))
+	assert.False(t, goref.Corpus("/a/b/c").Contains("/a/b/d"))
+	assert.False(t, goref.Corpus("/a/b/c").Contains("/"))
+	assert.False(t, goref.Corpus("/a/b/c").Contains("/a/b/"))
+}
+
+func TestRel(t *testing.T) {
+	assert.Equal(t, "d",
+		goref.Corpus("/a/b/c").Rel("/a/b/c/d"))
+	assert.Equal(t, ".",
+		goref.Corpus("/a/b/c/d").Rel("/a/b/c/d"))
+	assert.Equal(t, "a/b/c/d",
+		goref.Corpus("/").Rel("/a/b/c/d"))
+	assert.Equal(t, "/a/b/d",
+		goref.Corpus("/a/b/c").Rel("/a/b/d"))
+	assert.Equal(t, "/",
+		goref.Corpus("/a/b/c").Rel("/"))
+	assert.Equal(t, "/a/b/",
+		goref.Corpus("/a/b/c").Rel("/a/b/"))
+}