imports: ignore case and hyphens when lexically filtering candidate dirs

This means a directory /gopath/src/foo/Go-Bar is considered as maybe
containing package "bar" or even "gobar".

Also, more tests.

Fixes golang/go#16402

Change-Id: I14208d738e3a081cb6d9bcd83d777280e118f4e7
Reviewed-on: https://go-review.googlesource.com/25030
Reviewed-by: Andrew Gerrand <adg@golang.org>

imports/fix.go

@@ -644,28 +644,11 @@ func findImportGoPath(pkgName string, symbols map[string]bool, filename string)
 	}
 
 	var candidates []*pkg
-
 	for _, pkg := range dirScan {
-		if !strings.Contains(lastTwoComponents(pkg.importPathShort), pkgName) {
-			// Speed optimization to minimize disk I/O:
-			// the last two components on disk must contain the
-			// package name somewhere.
-			//
-			// This permits mismatch naming like directory
-			// "go-foo" being package "foo", or "pkg.v3" being "pkg",
-			// or directory "google.golang.org/api/cloudbilling/v1"
-			// being package "cloudbilling", but doesn't
-			// permit a directory "foo" to be package
-			// "bar", which is strongly discouraged
-			// anyway. There's no reason goimports needs
-			// to be slow just to accomodate that.
-			continue
-		}
-		if !canUse(filename, pkg.dir) {
-			continue
-		}
+		if pkgIsCandidate(filename, pkgName, pkg) {
 			candidates = append(candidates, pkg)
 		}
+	}
 
 	sort.Sort(byImportPathShortLength(candidates))
 	if Debug {
@@ -724,6 +707,76 @@ func findImportGoPath(pkgName string, symbols map[string]bool, filename string)
 	return "", false, nil
 }
 
+// pkgIsCandidate reports whether pkg is a candidate for satisfying the
+// finding which package pkgIdent in the file named by filename is trying
+// to refer to.
+//
+// This check is purely lexical and is meant to be as fast as possible
+// because it's run over all $GOPATH directories to filter out poor
+// candidates in order to limit the CPU and I/O later parsing the
+// exports in candidate packages.
+//
+// filename is the file being formatted.
+// pkgIdent is the package being searched for, like "client" (if
+// searching for "client.New")
+func pkgIsCandidate(filename, pkgIdent string, pkg *pkg) bool {
+	// Check "internal" and "vendor" visibility:
+	if !canUse(filename, pkg.dir) {
+		return false
+	}
+
+	// Speed optimization to minimize disk I/O:
+	// the last two components on disk must contain the
+	// package name somewhere.
+	//
+	// This permits mismatch naming like directory
+	// "go-foo" being package "foo", or "pkg.v3" being "pkg",
+	// or directory "google.golang.org/api/cloudbilling/v1"
+	// being package "cloudbilling", but doesn't
+	// permit a directory "foo" to be package
+	// "bar", which is strongly discouraged
+	// anyway. There's no reason goimports needs
+	// to be slow just to accomodate that.
+	lastTwo := lastTwoComponents(pkg.importPathShort)
+	if strings.Contains(lastTwo, pkgIdent) {
+		return true
+	}
+	if hasHyphenOrUpperASCII(lastTwo) && !hasHyphenOrUpperASCII(pkgIdent) {
+		lastTwo = lowerASCIIAndRemoveHyphen(lastTwo)
+		if strings.Contains(lastTwo, pkgIdent) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func hasHyphenOrUpperASCII(s string) bool {
+	for i := 0; i < len(s); i++ {
+		b := s[i]
+		if b == '-' || ('A' <= b && b <= 'Z') {
+			return true
+		}
+	}
+	return false
+}
+
+func lowerASCIIAndRemoveHyphen(s string) (ret string) {
+	buf := make([]byte, 0, len(s))
+	for i := 0; i < len(s); i++ {
+		b := s[i]
+		switch {
+		case b == '-':
+			continue
+		case 'A' <= b && b <= 'Z':
+			buf = append(buf, b+('a'-'A'))
+		default:
+			buf = append(buf, b)
+		}
+	}
+	return string(buf)
+}
+
 // canUse reports whether the package in dir is usable from filename,
 // respecting the Go "internal" and "vendor" visibility rules.
 func canUse(filename, dir string) bool {

imports/fix_test.go

@@ -1333,3 +1333,141 @@ func strSet(ss []string) map[string]bool {
 	}
 	return m
 }
+
+func TestPkgIsCandidate(t *testing.T) {
+	tests := [...]struct {
+		filename string
+		pkgIdent string
+		pkg      *pkg
+		want     bool
+	}{
+		// normal match
+		0: {
+			filename: "/gopath/src/my/pkg/pkg.go",
+			pkgIdent: "client",
+			pkg: &pkg{
+				dir:             "/gopath/src/client",
+				importPath:      "client",
+				importPathShort: "client",
+			},
+			want: true,
+		},
+		// not a match
+		1: {
+			filename: "/gopath/src/my/pkg/pkg.go",
+			pkgIdent: "zzz",
+			pkg: &pkg{
+				dir:             "/gopath/src/client",
+				importPath:      "client",
+				importPathShort: "client",
+			},
+			want: false,
+		},
+		// would be a match, but "client" appears too deep.
+		2: {
+			filename: "/gopath/src/my/pkg/pkg.go",
+			pkgIdent: "client",
+			pkg: &pkg{
+				dir:             "/gopath/src/client/foo/foo/foo",
+				importPath:      "client/foo/foo",
+				importPathShort: "client/foo/foo",
+			},
+			want: false,
+		},
+		// not an exact match, but substring is good enough.
+		3: {
+			filename: "/gopath/src/my/pkg/pkg.go",
+			pkgIdent: "client",
+			pkg: &pkg{
+				dir:             "/gopath/src/foo/go-client",
+				importPath:      "foo/go-client",
+				importPathShort: "foo/go-client",
+			},
+			want: true,
+		},
+		// "internal" package, and not visible
+		4: {
+			filename: "/gopath/src/my/pkg/pkg.go",
+			pkgIdent: "client",
+			pkg: &pkg{
+				dir:             "/gopath/src/foo/internal/client",
+				importPath:      "foo/internal/client",
+				importPathShort: "foo/internal/client",
+			},
+			want: false,
+		},
+		// "internal" package but visible
+		5: {
+			filename: "/gopath/src/foo/bar.go",
+			pkgIdent: "client",
+			pkg: &pkg{
+				dir:             "/gopath/src/foo/internal/client",
+				importPath:      "foo/internal/client",
+				importPathShort: "foo/internal/client",
+			},
+			want: true,
+		},
+		// "vendor" package not visible
+		6: {
+			filename: "/gopath/src/foo/bar.go",
+			pkgIdent: "client",
+			pkg: &pkg{
+				dir:             "/gopath/src/other/vendor/client",
+				importPath:      "other/vendor/client",
+				importPathShort: "client",
+			},
+			want: false,
+		},
+		// "vendor" package, visible
+		7: {
+			filename: "/gopath/src/foo/bar.go",
+			pkgIdent: "client",
+			pkg: &pkg{
+				dir:             "/gopath/src/foo/vendor/client",
+				importPath:      "other/foo/client",
+				importPathShort: "client",
+			},
+			want: true,
+		},
+		// Ignore hyphens.
+		8: {
+			filename: "/gopath/src/foo/bar.go",
+			pkgIdent: "socketio",
+			pkg: &pkg{
+				dir:             "/gopath/src/foo/socket-io",
+				importPath:      "foo/socket-io",
+				importPathShort: "foo/socket-io",
+			},
+			want: true,
+		},
+		// Ignore case.
+		9: {
+			filename: "/gopath/src/foo/bar.go",
+			pkgIdent: "fooprod",
+			pkg: &pkg{
+				dir:             "/gopath/src/foo/FooPROD",
+				importPath:      "foo/FooPROD",
+				importPathShort: "foo/FooPROD",
+			},
+			want: true,
+		},
+		// Ignoring both hyphens and case together.
+		10: {
+			filename: "/gopath/src/foo/bar.go",
+			pkgIdent: "fooprod",
+			pkg: &pkg{
+				dir:             "/gopath/src/foo/Foo-PROD",
+				importPath:      "foo/Foo-PROD",
+				importPathShort: "foo/Foo-PROD",
+			},
+			want: true,
+		},
+	}
+	for i, tt := range tests {
+		got := pkgIsCandidate(tt.filename, tt.pkgIdent, tt.pkg)
+		if got != tt.want {
+			t.Errorf("test %d. pkgIsCandidate(%q, %q, %+v) = %v; want %v",
+				i, tt.filename, tt.pkgIdent, *tt.pkg, got, tt.want)
+		}
+	}
+}