✨ Cross-module support for filesystem paths

pkg/loader/loader.go

@@ -1,5 +1,5 @@
 /*
-Copyright 2019 The Kubernetes Authors.
+Copyright 2019-2022 The Kubernetes Authors.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -25,9 +25,12 @@ import (
 	"go/types"
 	"io/ioutil"
 	"os"
+	"path/filepath"
+	"regexp"
 	"sync"
 
 	"golang.org/x/tools/go/packages"
+	"k8s.io/apimachinery/pkg/util/sets"
 )
 
 // Much of this is strongly inspired by the contents of go/packages,
@@ -329,6 +332,40 @@ func LoadRoots(roots ...string) ([]*Package, error) {
 //
 // This is generally only useful for use in testing when you need to modify
 // loading settings to load from a fake location.
+//
+// This function will traverse Go module boundaries for roots that are file-
+// system paths and end with "...". Please note this feature currently only
+// supports roots that are filesystem paths. For more information, please
+// refer to the high-level outline of this function's logic:
+//
+//     1. If no roots are provided then load the working directory and return
+//        early.
+//
+//     2. Otherwise sort the provided roots into two, distinct buckets:
+//
+//            a. package/module names
+//            b. filesystem paths
+//
+//        A filesystem path is distinguished from a Go package/module name by
+//        the same rules as followed by the "go" command. At a high level, a
+//        root is a filesystem path IFF it meets ANY of the following criteria:
+//
+//            * is absolute
+//            * begins with .
+//            * begins with ..
+//
+//        For more information please refer to the output of the command
+//        "go help packages".
+//
+//     3. Load the package/module roots as a single call to packages.Load. If
+//        there are no filesystem path roots then return early.
+//
+//     4. For filesystem path roots ending with "...", check to see if its
+//        descendants include any nested, Go modules. If so, add the directory
+//        that contains the nested Go module to the filesystem path roots.
+//
+//     5. Load the filesystem path roots and return the load packages for the
+//        package/module roots AND the filesystem path roots.
 func LoadRootsWithConfig(cfg *packages.Config, roots ...string) ([]*Package, error) {
 	l := &loader{
 		cfg:      cfg,
@@ -341,13 +378,208 @@ func LoadRootsWithConfig(cfg *packages.Config, roots ...string) ([]*Package, err
 	// put our build flags first so that callers can override them
 	l.cfg.BuildFlags = append([]string{"-tags", "ignore_autogenerated"}, l.cfg.BuildFlags...)
 
-	rawPkgs, err := packages.Load(l.cfg, roots...)
-	if err != nil {
-		return nil, err
+	// uniquePkgIDs is used to keep track of the discovered packages to be nice
+	// and try and prevent packages from showing up twice when nested module
+	// support is enabled. there is not harm that comes from this per se, but
+	// it makes testing easier when a known number of modules can be asserted
+	uniquePkgIDs := sets.String{}
+
+	// loadPackages returns the Go packages for the provided roots
+	//
+	// if validatePkgFn is nil, a package will be returned in the slice,
+	// otherwise the package is only returned if the result of
+	// validatePkgFn(pkg.ID) is truthy
+	loadPackages := func(roots ...string) ([]*Package, error) {
+		rawPkgs, err := packages.Load(l.cfg, roots...)
+		if err != nil {
+			return nil, err
+		}
+		var pkgs []*Package
+		for _, rp := range rawPkgs {
+			p := l.packageFor(rp)
+			if !uniquePkgIDs.Has(p.ID) {
+				pkgs = append(pkgs, p)
+				uniquePkgIDs.Insert(p.ID)
+			}
+		}
+		return pkgs, nil
+	}
+
+	// if no roots were provided then load the current package and return early
+	if len(roots) == 0 {
+		pkgs, err := loadPackages()
+		if err != nil {
+			return nil, err
+		}
+		l.Roots = append(l.Roots, pkgs...)
+		return l.Roots, nil
+	}
+
+	// pkgRoots is a slice of roots that are package/modules and fspRoots
+	// is a slice of roots that are local filesystem paths.
+	//
+	// please refer to this function's godoc comments for more information on
+	// how these two types of roots are distinguished from one another
+	var (
+		pkgRoots  []string
+		fspRoots  []string
+		fspRootRx = regexp.MustCompile(`^\.{1,2}`)
+	)
+	for _, r := range roots {
+		if filepath.IsAbs(r) || fspRootRx.MatchString(r) {
+			fspRoots = append(fspRoots, r)
+		} else {
+			pkgRoots = append(pkgRoots, r)
+		}
+	}
+
+	// handle the package roots by sending them into the packages.Load function
+	// all at once. this is more efficient, but cannot be used for the file-
+	// system path roots due to them needing a custom, calculated value for the
+	// cfg.Dir field
+	if len(pkgRoots) > 0 {
+		pkgs, err := loadPackages(pkgRoots...)
+		if err != nil {
+			return nil, err
+		}
+		l.Roots = append(l.Roots, pkgs...)
+	}
+
+	// if there are no filesystem path roots then go ahead and return early
+	if len(fspRoots) == 0 {
+		return l.Roots, nil
+	}
+
+	//
+	// at this point we are handling filesystem path roots
+	//
+
+	// ensure the cfg.Dir field is reset to its original value upon
+	// returning from this function. it should honestly be fine if it is
+	// not given most callers will not send in the cfg parameter directly,
+	// as it's largely for testing, but still, let's be good stewards.
+	defer func(d string) {
+		cfg.Dir = d
+	}(cfg.Dir)
+
+	// store the value of cfg.Dir so we can use it later if it is non-empty.
+	// we need to store it now as the value of cfg.Dir will be updated by
+	// a loop below
+	cfgDir := cfg.Dir
+
+	// addNestedGoModulesToRoots is given to filepath.WalkDir and adds the
+	// directory part of p to the list of filesystem path roots IFF p is the
+	// path to a file named "go.mod"
+	addNestedGoModulesToRoots := func(
+		p string,
+		d os.DirEntry,
+		e error) error {
+
+		if e != nil {
+			return e
+		}
+		if !d.IsDir() && filepath.Base(p) == "go.mod" {
+			fspRoots = append(fspRoots, filepath.Join(filepath.Dir(p), "..."))
+		}
+		return nil
 	}
 
-	for _, rawPkg := range rawPkgs {
-		l.Roots = append(l.Roots, l.packageFor(rawPkg))
+	// in the first pass over the filesystem path roots we:
+	//
+	//    1. make the root into an absolute path
+	//
+	//    2. check to see if a root uses the nested path syntax, ex. ...
+	//
+	//    3. if so, walk the root's descendants, searching for any nested Go
+	//       modules
+	//
+	//    4. if found then the directory containing the Go module is added to
+	//       the list of the filesystem path roots
+	for i := range fspRoots {
+		r := fspRoots[i]
+
+		// clean up the root
+		r = filepath.Clean(r)
+
+		// get the absolute path of the root
+		if !filepath.IsAbs(r) {
+
+			// if the initial value of cfg.Dir was non-empty then use it when
+			// building the absolute path to this root. otherwise use the
+			// filepath.Abs function to get the absolute path of the root based
+			// on the working directory
+			if cfgDir != "" {
+				r = filepath.Join(cfgDir, r)
+			} else {
+				ar, err := filepath.Abs(r)
+				if err != nil {
+					return nil, err
+				}
+				r = ar
+			}
+		}
+
+		// update the root to be an absolute path
+		fspRoots[i] = r
+
+		b, d := filepath.Base(r), filepath.Dir(r)
+
+		// if the base element is "..." then it means nested traversal is
+		// activated. this can be passed directly to the loader. however, if
+		// specified we also want to traverse the path manually to determine if
+		// there are any nested Go modules we want to add to the list of file-
+		// system path roots to process
+		if b == "..." {
+			if err := filepath.WalkDir(
+				d,
+				addNestedGoModulesToRoots); err != nil {
+
+				return nil, err
+			}
+		}
+	}
+
+	// in the second pass over the filesystem path roots we:
+	//
+	//    1. determine the directory from which to execute the loader
+	//
+	//    2. update the loader config's Dir property to be the directory from
+	//       step one
+	//
+	//    3. determine whether the root passed to the loader should be "./."
+	//       or "./..."
+	//
+	//    4. execute the loader with the value from step three
+	for _, r := range fspRoots {
+		b, d := filepath.Base(r), filepath.Dir(r)
+
+		// we want the base part of the path to be either "..." or ".", except
+		// Go's filepath utilities clean paths during manipulation, removing the
+		// ".". thus, if not "...", let's update the path components so that:
+		//
+		//   d = r
+		//   b = "."
+		if b != "..." {
+			d = r
+			b = "."
+		}
+
+		// update the loader configuration's Dir field to the directory part of
+		// the root
+		l.cfg.Dir = d
+
+		// update the root to be "./..." or "./."
+		// (with OS-specific filepath separator). please note filepath.Join
+		// would clean up the trailing "." character that we want preserved,
+		// hence the more manual path concatenation logic
+		r = fmt.Sprintf(".%s%s", string(filepath.Separator), b)
+
+		// load the packages from the roots
+		pkgs, err := loadPackages(r)
+		if err != nil {
+			return nil, err
+		}
+		l.Roots = append(l.Roots, pkgs...)
 	}
 
 	return l.Roots, nil

pkg/loader/loader_suite_test.go

@@ -0,0 +1,29 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package loader_test
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+func TestLoader(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Loader Patching Suite")
+}