feat(application): inital commit

vendor/golang.org/x/tools/go/packages/doc.go

@@ -0,0 +1,220 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package packages loads Go packages for inspection and analysis.
+
+The Load function takes as input a list of patterns and return a list of Package
+structs describing individual packages matched by those patterns.
+The LoadMode controls the amount of detail in the loaded packages.
+
+Load passes most patterns directly to the underlying build tool,
+but all patterns with the prefix "query=", where query is a
+non-empty string of letters from [a-z], are reserved and may be
+interpreted as query operators.
+
+Two query operators are currently supported: "file" and "pattern".
+
+The query "file=path/to/file.go" matches the package or packages enclosing
+the Go source file path/to/file.go.  For example "file=~/go/src/fmt/print.go"
+might return the packages "fmt" and "fmt [fmt.test]".
+
+The query "pattern=string" causes "string" to be passed directly to
+the underlying build tool. In most cases this is unnecessary,
+but an application can use Load("pattern=" + x) as an escaping mechanism
+to ensure that x is not interpreted as a query operator if it contains '='.
+
+All other query operators are reserved for future use and currently
+cause Load to report an error.
+
+The Package struct provides basic information about the package, including
+
+  - ID, a unique identifier for the package in the returned set;
+  - GoFiles, the names of the package's Go source files;
+  - Imports, a map from source import strings to the Packages they name;
+  - Types, the type information for the package's exported symbols;
+  - Syntax, the parsed syntax trees for the package's source code; and
+  - TypeInfo, the result of a complete type-check of the package syntax trees.
+
+(See the documentation for type Package for the complete list of fields
+and more detailed descriptions.)
+
+For example,
+
+	Load(nil, "bytes", "unicode...")
+
+returns four Package structs describing the standard library packages
+bytes, unicode, unicode/utf16, and unicode/utf8. Note that one pattern
+can match multiple packages and that a package might be matched by
+multiple patterns: in general it is not possible to determine which
+packages correspond to which patterns.
+
+Note that the list returned by Load contains only the packages matched
+by the patterns. Their dependencies can be found by walking the import
+graph using the Imports fields.
+
+The Load function can be configured by passing a pointer to a Config as
+the first argument. A nil Config is equivalent to the zero Config, which
+causes Load to run in LoadFiles mode, collecting minimal information.
+See the documentation for type Config for details.
+
+As noted earlier, the Config.Mode controls the amount of detail
+reported about the loaded packages. See the documentation for type LoadMode
+for details.
+
+Most tools should pass their command-line arguments (after any flags)
+uninterpreted to the loader, so that the loader can interpret them
+according to the conventions of the underlying build system.
+See the Example function for typical usage.
+*/
+package packages // import "golang.org/x/tools/go/packages"
+
+/*
+
+Motivation and design considerations
+
+The new package's design solves problems addressed by two existing
+packages: go/build, which locates and describes packages, and
+golang.org/x/tools/go/loader, which loads, parses and type-checks them.
+The go/build.Package structure encodes too much of the 'go build' way
+of organizing projects, leaving us in need of a data type that describes a
+package of Go source code independent of the underlying build system.
+We wanted something that works equally well with go build and vgo, and
+also other build systems such as Bazel and Blaze, making it possible to
+construct analysis tools that work in all these environments.
+Tools such as errcheck and staticcheck were essentially unavailable to
+the Go community at Google, and some of Google's internal tools for Go
+are unavailable externally.
+This new package provides a uniform way to obtain package metadata by
+querying each of these build systems, optionally supporting their
+preferred command-line notations for packages, so that tools integrate
+neatly with users' build environments. The Metadata query function
+executes an external query tool appropriate to the current workspace.
+
+Loading packages always returns the complete import graph "all the way down",
+even if all you want is information about a single package, because the query
+mechanisms of all the build systems we currently support ({go,vgo} list, and
+blaze/bazel aspect-based query) cannot provide detailed information
+about one package without visiting all its dependencies too, so there is
+no additional asymptotic cost to providing transitive information.
+(This property might not be true of a hypothetical 5th build system.)
+
+In calls to TypeCheck, all initial packages, and any package that
+transitively depends on one of them, must be loaded from source.
+Consider A->B->C->D->E: if A,C are initial, A,B,C must be loaded from
+source; D may be loaded from export data, and E may not be loaded at all
+(though it's possible that D's export data mentions it, so a
+types.Package may be created for it and exposed.)
+
+The old loader had a feature to suppress type-checking of function
+bodies on a per-package basis, primarily intended to reduce the work of
+obtaining type information for imported packages. Now that imports are
+satisfied by export data, the optimization no longer seems necessary.
+
+Despite some early attempts, the old loader did not exploit export data,
+instead always using the equivalent of WholeProgram mode. This was due
+to the complexity of mixing source and export data packages (now
+resolved by the upward traversal mentioned above), and because export data
+files were nearly always missing or stale. Now that 'go build' supports
+caching, all the underlying build systems can guarantee to produce
+export data in a reasonable (amortized) time.
+
+Test "main" packages synthesized by the build system are now reported as
+first-class packages, avoiding the need for clients (such as go/ssa) to
+reinvent this generation logic.
+
+One way in which go/packages is simpler than the old loader is in its
+treatment of in-package tests. In-package tests are packages that
+consist of all the files of the library under test, plus the test files.
+The old loader constructed in-package tests by a two-phase process of
+mutation called "augmentation": first it would construct and type check
+all the ordinary library packages and type-check the packages that
+depend on them; then it would add more (test) files to the package and
+type-check again. This two-phase approach had four major problems:
+1) in processing the tests, the loader modified the library package,
+   leaving no way for a client application to see both the test
+   package and the library package; one would mutate into the other.
+2) because test files can declare additional methods on types defined in
+   the library portion of the package, the dispatch of method calls in
+   the library portion was affected by the presence of the test files.
+   This should have been a clue that the packages were logically
+   different.
+3) this model of "augmentation" assumed at most one in-package test
+   per library package, which is true of projects using 'go build',
+   but not other build systems.
+4) because of the two-phase nature of test processing, all packages that
+   import the library package had to be processed before augmentation,
+   forcing a "one-shot" API and preventing the client from calling Load
+   in several times in sequence as is now possible in WholeProgram mode.
+   (TypeCheck mode has a similar one-shot restriction for a different reason.)
+
+Early drafts of this package supported "multi-shot" operation.
+Although it allowed clients to make a sequence of calls (or concurrent
+calls) to Load, building up the graph of Packages incrementally,
+it was of marginal value: it complicated the API
+(since it allowed some options to vary across calls but not others),
+it complicated the implementation,
+it cannot be made to work in Types mode, as explained above,
+and it was less efficient than making one combined call (when this is possible).
+Among the clients we have inspected, none made multiple calls to load
+but could not be easily and satisfactorily modified to make only a single call.
+However, applications changes may be required.
+For example, the ssadump command loads the user-specified packages
+and in addition the runtime package.  It is tempting to simply append
+"runtime" to the user-provided list, but that does not work if the user
+specified an ad-hoc package such as [a.go b.go].
+Instead, ssadump no longer requests the runtime package,
+but seeks it among the dependencies of the user-specified packages,
+and emits an error if it is not found.
+
+Overlays: The Overlay field in the Config allows providing alternate contents
+for Go source files, by providing a mapping from file path to contents.
+go/packages will pull in new imports added in overlay files when go/packages
+is run in LoadImports mode or greater.
+Overlay support for the go list driver isn't complete yet: if the file doesn't
+exist on disk, it will only be recognized in an overlay if it is a non-test file
+and the package would be reported even without the overlay.
+
+Questions & Tasks
+
+- Add GOARCH/GOOS?
+  They are not portable concepts, but could be made portable.
+  Our goal has been to allow users to express themselves using the conventions
+  of the underlying build system: if the build system honors GOARCH
+  during a build and during a metadata query, then so should
+  applications built atop that query mechanism.
+  Conversely, if the target architecture of the build is determined by
+  command-line flags, the application can pass the relevant
+  flags through to the build system using a command such as:
+    myapp -query_flag="--cpu=amd64" -query_flag="--os=darwin"
+  However, this approach is low-level, unwieldy, and non-portable.
+  GOOS and GOARCH seem important enough to warrant a dedicated option.
+
+- How should we handle partial failures such as a mixture of good and
+  malformed patterns, existing and non-existent packages, successful and
+  failed builds, import failures, import cycles, and so on, in a call to
+  Load?
+
+- Support bazel, blaze, and go1.10 list, not just go1.11 list.
+
+- Handle (and test) various partial success cases, e.g.
+  a mixture of good packages and:
+  invalid patterns
+  nonexistent packages
+  empty packages
+  packages with malformed package or import declarations
+  unreadable files
+  import cycles
+  other parse errors
+  type errors
+  Make sure we record errors at the correct place in the graph.
+
+- Missing packages among initial arguments are not reported.
+  Return bogus packages for them, like golist does.
+
+- "undeclared name" errors (for example) are reported out of source file
+  order. I suspect this is due to the breadth-first resolution now used
+  by go/types. Is that a bug? Discuss with gri.
+
+*/

vendor/golang.org/x/tools/go/packages/external.go

@@ -0,0 +1,101 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file enables an external tool to intercept package requests.
+// If the tool is present then its results are used in preference to
+// the go list command.
+
+package packages
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	exec "golang.org/x/sys/execabs"
+	"os"
+	"strings"
+)
+
+// The Driver Protocol
+//
+// The driver, given the inputs to a call to Load, returns metadata about the packages specified.
+// This allows for different build systems to support go/packages by telling go/packages how the
+// packages' source is organized.
+// The driver is a binary, either specified by the GOPACKAGESDRIVER environment variable or in
+// the path as gopackagesdriver. It's given the inputs to load in its argv. See the package
+// documentation in doc.go for the full description of the patterns that need to be supported.
+// A driver receives as a JSON-serialized driverRequest struct in standard input and will
+// produce a JSON-serialized driverResponse (see definition in packages.go) in its standard output.
+
+// driverRequest is used to provide the portion of Load's Config that is needed by a driver.
+type driverRequest struct {
+	Mode LoadMode `json:"mode"`
+	// Env specifies the environment the underlying build system should be run in.
+	Env []string `json:"env"`
+	// BuildFlags are flags that should be passed to the underlying build system.
+	BuildFlags []string `json:"build_flags"`
+	// Tests specifies whether the patterns should also return test packages.
+	Tests bool `json:"tests"`
+	// Overlay maps file paths (relative to the driver's working directory) to the byte contents
+	// of overlay files.
+	Overlay map[string][]byte `json:"overlay"`
+}
+
+// findExternalDriver returns the file path of a tool that supplies
+// the build system package structure, or "" if not found."
+// If GOPACKAGESDRIVER is set in the environment findExternalTool returns its
+// value, otherwise it searches for a binary named gopackagesdriver on the PATH.
+func findExternalDriver(cfg *Config) driver {
+	const toolPrefix = "GOPACKAGESDRIVER="
+	tool := ""
+	for _, env := range cfg.Env {
+		if val := strings.TrimPrefix(env, toolPrefix); val != env {
+			tool = val
+		}
+	}
+	if tool != "" && tool == "off" {
+		return nil
+	}
+	if tool == "" {
+		var err error
+		tool, err = exec.LookPath("gopackagesdriver")
+		if err != nil {
+			return nil
+		}
+	}
+	return func(cfg *Config, words ...string) (*driverResponse, error) {
+		req, err := json.Marshal(driverRequest{
+			Mode:       cfg.Mode,
+			Env:        cfg.Env,
+			BuildFlags: cfg.BuildFlags,
+			Tests:      cfg.Tests,
+			Overlay:    cfg.Overlay,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("failed to encode message to driver tool: %v", err)
+		}
+
+		buf := new(bytes.Buffer)
+		stderr := new(bytes.Buffer)
+		cmd := exec.CommandContext(cfg.Context, tool, words...)
+		cmd.Dir = cfg.Dir
+		cmd.Env = cfg.Env
+		cmd.Stdin = bytes.NewReader(req)
+		cmd.Stdout = buf
+		cmd.Stderr = stderr
+
+		if err := cmd.Run(); err != nil {
+			return nil, fmt.Errorf("%v: %v: %s", tool, err, cmd.Stderr)
+		}
+		if len(stderr.Bytes()) != 0 && os.Getenv("GOPACKAGESPRINTDRIVERERRORS") != "" {
+			fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(cmd), stderr)
+		}
+
+		var response driverResponse
+		if err := json.Unmarshal(buf.Bytes(), &response); err != nil {
+			return nil, err
+		}
+		return &response, nil
+	}
+}

vendor/golang.org/x/tools/go/packages/golist_overlay.go

@@ -0,0 +1,575 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"encoding/json"
+	"fmt"
+	"go/parser"
+	"go/token"
+	"os"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/internal/gocommand"
+)
+
+// processGolistOverlay provides rudimentary support for adding
+// files that don't exist on disk to an overlay. The results can be
+// sometimes incorrect.
+// TODO(matloob): Handle unsupported cases, including the following:
+// - determining the correct package to add given a new import path
+func (state *golistState) processGolistOverlay(response *responseDeduper) (modifiedPkgs, needPkgs []string, err error) {
+	havePkgs := make(map[string]string) // importPath -> non-test package ID
+	needPkgsSet := make(map[string]bool)
+	modifiedPkgsSet := make(map[string]bool)
+
+	pkgOfDir := make(map[string][]*Package)
+	for _, pkg := range response.dr.Packages {
+		// This is an approximation of import path to id. This can be
+		// wrong for tests, vendored packages, and a number of other cases.
+		havePkgs[pkg.PkgPath] = pkg.ID
+		dir, err := commonDir(pkg.GoFiles)
+		if err != nil {
+			return nil, nil, err
+		}
+		if dir != "" {
+			pkgOfDir[dir] = append(pkgOfDir[dir], pkg)
+		}
+	}
+
+	// If no new imports are added, it is safe to avoid loading any needPkgs.
+	// Otherwise, it's hard to tell which package is actually being loaded
+	// (due to vendoring) and whether any modified package will show up
+	// in the transitive set of dependencies (because new imports are added,
+	// potentially modifying the transitive set of dependencies).
+	var overlayAddsImports bool
+
+	// If both a package and its test package are created by the overlay, we
+	// need the real package first. Process all non-test files before test
+	// files, and make the whole process deterministic while we're at it.
+	var overlayFiles []string
+	for opath := range state.cfg.Overlay {
+		overlayFiles = append(overlayFiles, opath)
+	}
+	sort.Slice(overlayFiles, func(i, j int) bool {
+		iTest := strings.HasSuffix(overlayFiles[i], "_test.go")
+		jTest := strings.HasSuffix(overlayFiles[j], "_test.go")
+		if iTest != jTest {
+			return !iTest // non-tests are before tests.
+		}
+		return overlayFiles[i] < overlayFiles[j]
+	})
+	for _, opath := range overlayFiles {
+		contents := state.cfg.Overlay[opath]
+		base := filepath.Base(opath)
+		dir := filepath.Dir(opath)
+		var pkg *Package           // if opath belongs to both a package and its test variant, this will be the test variant
+		var testVariantOf *Package // if opath is a test file, this is the package it is testing
+		var fileExists bool
+		isTestFile := strings.HasSuffix(opath, "_test.go")
+		pkgName, ok := extractPackageName(opath, contents)
+		if !ok {
+			// Don't bother adding a file that doesn't even have a parsable package statement
+			// to the overlay.
+			continue
+		}
+		// If all the overlay files belong to a different package, change the
+		// package name to that package.
+		maybeFixPackageName(pkgName, isTestFile, pkgOfDir[dir])
+	nextPackage:
+		for _, p := range response.dr.Packages {
+			if pkgName != p.Name && p.ID != "command-line-arguments" {
+				continue
+			}
+			for _, f := range p.GoFiles {
+				if !sameFile(filepath.Dir(f), dir) {
+					continue
+				}
+				// Make sure to capture information on the package's test variant, if needed.
+				if isTestFile && !hasTestFiles(p) {
+					// TODO(matloob): Are there packages other than the 'production' variant
+					// of a package that this can match? This shouldn't match the test main package
+					// because the file is generated in another directory.
+					testVariantOf = p
+					continue nextPackage
+				} else if !isTestFile && hasTestFiles(p) {
+					// We're examining a test variant, but the overlaid file is
+					// a non-test file. Because the overlay implementation
+					// (currently) only adds a file to one package, skip this
+					// package, so that we can add the file to the production
+					// variant of the package. (https://golang.org/issue/36857
+					// tracks handling overlays on both the production and test
+					// variant of a package).
+					continue nextPackage
+				}
+				if pkg != nil && p != pkg && pkg.PkgPath == p.PkgPath {
+					// We have already seen the production version of the
+					// for which p is a test variant.
+					if hasTestFiles(p) {
+						testVariantOf = pkg
+					}
+				}
+				pkg = p
+				if filepath.Base(f) == base {
+					fileExists = true
+				}
+			}
+		}
+		// The overlay could have included an entirely new package or an
+		// ad-hoc package. An ad-hoc package is one that we have manually
+		// constructed from inadequate `go list` results for a file= query.
+		// It will have the ID command-line-arguments.
+		if pkg == nil || pkg.ID == "command-line-arguments" {
+			// Try to find the module or gopath dir the file is contained in.
+			// Then for modules, add the module opath to the beginning.
+			pkgPath, ok, err := state.getPkgPath(dir)
+			if err != nil {
+				return nil, nil, err
+			}
+			if !ok {
+				break
+			}
+			var forTest string // only set for x tests
+			isXTest := strings.HasSuffix(pkgName, "_test")
+			if isXTest {
+				forTest = pkgPath
+				pkgPath += "_test"
+			}
+			id := pkgPath
+			if isTestFile {
+				if isXTest {
+					id = fmt.Sprintf("%s [%s.test]", pkgPath, forTest)
+				} else {
+					id = fmt.Sprintf("%s [%s.test]", pkgPath, pkgPath)
+				}
+			}
+			if pkg != nil {
+				// TODO(rstambler): We should change the package's path and ID
+				// here. The only issue is that this messes with the roots.
+			} else {
+				// Try to reclaim a package with the same ID, if it exists in the response.
+				for _, p := range response.dr.Packages {
+					if reclaimPackage(p, id, opath, contents) {
+						pkg = p
+						break
+					}
+				}
+				// Otherwise, create a new package.
+				if pkg == nil {
+					pkg = &Package{
+						PkgPath: pkgPath,
+						ID:      id,
+						Name:    pkgName,
+						Imports: make(map[string]*Package),
+					}
+					response.addPackage(pkg)
+					havePkgs[pkg.PkgPath] = id
+					// Add the production package's sources for a test variant.
+					if isTestFile && !isXTest && testVariantOf != nil {
+						pkg.GoFiles = append(pkg.GoFiles, testVariantOf.GoFiles...)
+						pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, testVariantOf.CompiledGoFiles...)
+						// Add the package under test and its imports to the test variant.
+						pkg.forTest = testVariantOf.PkgPath
+						for k, v := range testVariantOf.Imports {
+							pkg.Imports[k] = &Package{ID: v.ID}
+						}
+					}
+					if isXTest {
+						pkg.forTest = forTest
+					}
+				}
+			}
+		}
+		if !fileExists {
+			pkg.GoFiles = append(pkg.GoFiles, opath)
+			// TODO(matloob): Adding the file to CompiledGoFiles can exhibit the wrong behavior
+			// if the file will be ignored due to its build tags.
+			pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, opath)
+			modifiedPkgsSet[pkg.ID] = true
+		}
+		imports, err := extractImports(opath, contents)
+		if err != nil {
+			// Let the parser or type checker report errors later.
+			continue
+		}
+		for _, imp := range imports {
+			// TODO(rstambler): If the package is an x test and the import has
+			// a test variant, make sure to replace it.
+			if _, found := pkg.Imports[imp]; found {
+				continue
+			}
+			overlayAddsImports = true
+			id, ok := havePkgs[imp]
+			if !ok {
+				var err error
+				id, err = state.resolveImport(dir, imp)
+				if err != nil {
+					return nil, nil, err
+				}
+			}
+			pkg.Imports[imp] = &Package{ID: id}
+			// Add dependencies to the non-test variant version of this package as well.
+			if testVariantOf != nil {
+				testVariantOf.Imports[imp] = &Package{ID: id}
+			}
+		}
+	}
+
+	// toPkgPath guesses the package path given the id.
+	toPkgPath := func(sourceDir, id string) (string, error) {
+		if i := strings.IndexByte(id, ' '); i >= 0 {
+			return state.resolveImport(sourceDir, id[:i])
+		}
+		return state.resolveImport(sourceDir, id)
+	}
+
+	// Now that new packages have been created, do another pass to determine
+	// the new set of missing packages.
+	for _, pkg := range response.dr.Packages {
+		for _, imp := range pkg.Imports {
+			if len(pkg.GoFiles) == 0 {
+				return nil, nil, fmt.Errorf("cannot resolve imports for package %q with no Go files", pkg.PkgPath)
+			}
+			pkgPath, err := toPkgPath(filepath.Dir(pkg.GoFiles[0]), imp.ID)
+			if err != nil {
+				return nil, nil, err
+			}
+			if _, ok := havePkgs[pkgPath]; !ok {
+				needPkgsSet[pkgPath] = true
+			}
+		}
+	}
+
+	if overlayAddsImports {
+		needPkgs = make([]string, 0, len(needPkgsSet))
+		for pkg := range needPkgsSet {
+			needPkgs = append(needPkgs, pkg)
+		}
+	}
+	modifiedPkgs = make([]string, 0, len(modifiedPkgsSet))
+	for pkg := range modifiedPkgsSet {
+		modifiedPkgs = append(modifiedPkgs, pkg)
+	}
+	return modifiedPkgs, needPkgs, err
+}
+
+// resolveImport finds the ID of a package given its import path.
+// In particular, it will find the right vendored copy when in GOPATH mode.
+func (state *golistState) resolveImport(sourceDir, importPath string) (string, error) {
+	env, err := state.getEnv()
+	if err != nil {
+		return "", err
+	}
+	if env["GOMOD"] != "" {
+		return importPath, nil
+	}
+
+	searchDir := sourceDir
+	for {
+		vendorDir := filepath.Join(searchDir, "vendor")
+		exists, ok := state.vendorDirs[vendorDir]
+		if !ok {
+			info, err := os.Stat(vendorDir)
+			exists = err == nil && info.IsDir()
+			state.vendorDirs[vendorDir] = exists
+		}
+
+		if exists {
+			vendoredPath := filepath.Join(vendorDir, importPath)
+			if info, err := os.Stat(vendoredPath); err == nil && info.IsDir() {
+				// We should probably check for .go files here, but shame on anyone who fools us.
+				path, ok, err := state.getPkgPath(vendoredPath)
+				if err != nil {
+					return "", err
+				}
+				if ok {
+					return path, nil
+				}
+			}
+		}
+
+		// We know we've hit the top of the filesystem when we Dir / and get /,
+		// or C:\ and get C:\, etc.
+		next := filepath.Dir(searchDir)
+		if next == searchDir {
+			break
+		}
+		searchDir = next
+	}
+	return importPath, nil
+}
+
+func hasTestFiles(p *Package) bool {
+	for _, f := range p.GoFiles {
+		if strings.HasSuffix(f, "_test.go") {
+			return true
+		}
+	}
+	return false
+}
+
+// determineRootDirs returns a mapping from absolute directories that could
+// contain code to their corresponding import path prefixes.
+func (state *golistState) determineRootDirs() (map[string]string, error) {
+	env, err := state.getEnv()
+	if err != nil {
+		return nil, err
+	}
+	if env["GOMOD"] != "" {
+		state.rootsOnce.Do(func() {
+			state.rootDirs, state.rootDirsError = state.determineRootDirsModules()
+		})
+	} else {
+		state.rootsOnce.Do(func() {
+			state.rootDirs, state.rootDirsError = state.determineRootDirsGOPATH()
+		})
+	}
+	return state.rootDirs, state.rootDirsError
+}
+
+func (state *golistState) determineRootDirsModules() (map[string]string, error) {
+	// List all of the modules--the first will be the directory for the main
+	// module. Any replaced modules will also need to be treated as roots.
+	// Editing files in the module cache isn't a great idea, so we don't
+	// plan to ever support that.
+	out, err := state.invokeGo("list", "-m", "-json", "all")
+	if err != nil {
+		// 'go list all' will fail if we're outside of a module and
+		// GO111MODULE=on. Try falling back without 'all'.
+		var innerErr error
+		out, innerErr = state.invokeGo("list", "-m", "-json")
+		if innerErr != nil {
+			return nil, err
+		}
+	}
+	roots := map[string]string{}
+	modules := map[string]string{}
+	var i int
+	for dec := json.NewDecoder(out); dec.More(); {
+		mod := new(gocommand.ModuleJSON)
+		if err := dec.Decode(mod); err != nil {
+			return nil, err
+		}
+		if mod.Dir != "" && mod.Path != "" {
+			// This is a valid module; add it to the map.
+			absDir, err := filepath.Abs(mod.Dir)
+			if err != nil {
+				return nil, err
+			}
+			modules[absDir] = mod.Path
+			// The first result is the main module.
+			if i == 0 || mod.Replace != nil && mod.Replace.Path != "" {
+				roots[absDir] = mod.Path
+			}
+		}
+		i++
+	}
+	return roots, nil
+}
+
+func (state *golistState) determineRootDirsGOPATH() (map[string]string, error) {
+	m := map[string]string{}
+	for _, dir := range filepath.SplitList(state.mustGetEnv()["GOPATH"]) {
+		absDir, err := filepath.Abs(dir)
+		if err != nil {
+			return nil, err
+		}
+		m[filepath.Join(absDir, "src")] = ""
+	}
+	return m, nil
+}
+
+func extractImports(filename string, contents []byte) ([]string, error) {
+	f, err := parser.ParseFile(token.NewFileSet(), filename, contents, parser.ImportsOnly) // TODO(matloob): reuse fileset?
+	if err != nil {
+		return nil, err
+	}
+	var res []string
+	for _, imp := range f.Imports {
+		quotedPath := imp.Path.Value
+		path, err := strconv.Unquote(quotedPath)
+		if err != nil {
+			return nil, err
+		}
+		res = append(res, path)
+	}
+	return res, nil
+}
+
+// reclaimPackage attempts to reuse a package that failed to load in an overlay.
+//
+// If the package has errors and has no Name, GoFiles, or Imports,
+// then it's possible that it doesn't yet exist on disk.
+func reclaimPackage(pkg *Package, id string, filename string, contents []byte) bool {
+	// TODO(rstambler): Check the message of the actual error?
+	// It differs between $GOPATH and module mode.
+	if pkg.ID != id {
+		return false
+	}
+	if len(pkg.Errors) != 1 {
+		return false
+	}
+	if pkg.Name != "" || pkg.ExportFile != "" {
+		return false
+	}
+	if len(pkg.GoFiles) > 0 || len(pkg.CompiledGoFiles) > 0 || len(pkg.OtherFiles) > 0 {
+		return false
+	}
+	if len(pkg.Imports) > 0 {
+		return false
+	}
+	pkgName, ok := extractPackageName(filename, contents)
+	if !ok {
+		return false
+	}
+	pkg.Name = pkgName
+	pkg.Errors = nil
+	return true
+}
+
+func extractPackageName(filename string, contents []byte) (string, bool) {
+	// TODO(rstambler): Check the message of the actual error?
+	// It differs between $GOPATH and module mode.
+	f, err := parser.ParseFile(token.NewFileSet(), filename, contents, parser.PackageClauseOnly) // TODO(matloob): reuse fileset?
+	if err != nil {
+		return "", false
+	}
+	return f.Name.Name, true
+}
+
+// commonDir returns the directory that all files are in, "" if files is empty,
+// or an error if they aren't in the same directory.
+func commonDir(files []string) (string, error) {
+	seen := make(map[string]bool)
+	for _, f := range files {
+		seen[filepath.Dir(f)] = true
+	}
+	if len(seen) > 1 {
+		return "", fmt.Errorf("files (%v) are in more than one directory: %v", files, seen)
+	}
+	for k := range seen {
+		// seen has only one element; return it.
+		return k, nil
+	}
+	return "", nil // no files
+}
+
+// It is possible that the files in the disk directory dir have a different package
+// name from newName, which is deduced from the overlays. If they all have a different
+// package name, and they all have the same package name, then that name becomes
+// the package name.
+// It returns true if it changes the package name, false otherwise.
+func maybeFixPackageName(newName string, isTestFile bool, pkgsOfDir []*Package) {
+	names := make(map[string]int)
+	for _, p := range pkgsOfDir {
+		names[p.Name]++
+	}
+	if len(names) != 1 {
+		// some files are in different packages
+		return
+	}
+	var oldName string
+	for k := range names {
+		oldName = k
+	}
+	if newName == oldName {
+		return
+	}
+	// We might have a case where all of the package names in the directory are
+	// the same, but the overlay file is for an x test, which belongs to its
+	// own package. If the x test does not yet exist on disk, we may not yet
+	// have its package name on disk, but we should not rename the packages.
+	//
+	// We use a heuristic to determine if this file belongs to an x test:
+	// The test file should have a package name whose package name has a _test
+	// suffix or looks like "newName_test".
+	maybeXTest := strings.HasPrefix(oldName+"_test", newName) || strings.HasSuffix(newName, "_test")
+	if isTestFile && maybeXTest {
+		return
+	}
+	for _, p := range pkgsOfDir {
+		p.Name = newName
+	}
+}
+
+// This function is copy-pasted from
+// https://github.com/golang/go/blob/9706f510a5e2754595d716bd64be8375997311fb/src/cmd/go/internal/search/search.go#L360.
+// It should be deleted when we remove support for overlays from go/packages.
+//
+// NOTE: This does not handle any ./... or ./ style queries, as this function
+// doesn't know the working directory.
+//
+// matchPattern(pattern)(name) reports whether
+// name matches pattern. Pattern is a limited glob
+// pattern in which '...' means 'any string' and there
+// is no other special syntax.
+// Unfortunately, there are two special cases. Quoting "go help packages":
+//
+// First, /... at the end of the pattern can match an empty string,
+// so that net/... matches both net and packages in its subdirectories, like net/http.
+// Second, any slash-separated pattern element containing a wildcard never
+// participates in a match of the "vendor" element in the path of a vendored
+// package, so that ./... does not match packages in subdirectories of
+// ./vendor or ./mycode/vendor, but ./vendor/... and ./mycode/vendor/... do.
+// Note, however, that a directory named vendor that itself contains code
+// is not a vendored package: cmd/vendor would be a command named vendor,
+// and the pattern cmd/... matches it.
+func matchPattern(pattern string) func(name string) bool {
+	// Convert pattern to regular expression.
+	// The strategy for the trailing /... is to nest it in an explicit ? expression.
+	// The strategy for the vendor exclusion is to change the unmatchable
+	// vendor strings to a disallowed code point (vendorChar) and to use
+	// "(anything but that codepoint)*" as the implementation of the ... wildcard.
+	// This is a bit complicated but the obvious alternative,
+	// namely a hand-written search like in most shell glob matchers,
+	// is too easy to make accidentally exponential.
+	// Using package regexp guarantees linear-time matching.
+
+	const vendorChar = "\x00"
+
+	if strings.Contains(pattern, vendorChar) {
+		return func(name string) bool { return false }
+	}
+
+	re := regexp.QuoteMeta(pattern)
+	re = replaceVendor(re, vendorChar)
+	switch {
+	case strings.HasSuffix(re, `/`+vendorChar+`/\.\.\.`):
+		re = strings.TrimSuffix(re, `/`+vendorChar+`/\.\.\.`) + `(/vendor|/` + vendorChar + `/\.\.\.)`
+	case re == vendorChar+`/\.\.\.`:
+		re = `(/vendor|/` + vendorChar + `/\.\.\.)`
+	case strings.HasSuffix(re, `/\.\.\.`):
+		re = strings.TrimSuffix(re, `/\.\.\.`) + `(/\.\.\.)?`
+	}
+	re = strings.ReplaceAll(re, `\.\.\.`, `[^`+vendorChar+`]*`)
+
+	reg := regexp.MustCompile(`^` + re + `$`)
+
+	return func(name string) bool {
+		if strings.Contains(name, vendorChar) {
+			return false
+		}
+		return reg.MatchString(replaceVendor(name, vendorChar))
+	}
+}
+
+// replaceVendor returns the result of replacing
+// non-trailing vendor path elements in x with repl.
+func replaceVendor(x, repl string) string {
+	if !strings.Contains(x, "vendor") {
+		return x
+	}
+	elem := strings.Split(x, "/")
+	for i := 0; i < len(elem)-1; i++ {
+		if elem[i] == "vendor" {
+			elem[i] = repl
+		}
+	}
+	return strings.Join(elem, "/")
+}

vendor/golang.org/x/tools/go/packages/loadmode_string.go

@@ -0,0 +1,57 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"fmt"
+	"strings"
+)
+
+var allModes = []LoadMode{
+	NeedName,
+	NeedFiles,
+	NeedCompiledGoFiles,
+	NeedImports,
+	NeedDeps,
+	NeedExportFile,
+	NeedTypes,
+	NeedSyntax,
+	NeedTypesInfo,
+	NeedTypesSizes,
+}
+
+var modeStrings = []string{
+	"NeedName",
+	"NeedFiles",
+	"NeedCompiledGoFiles",
+	"NeedImports",
+	"NeedDeps",
+	"NeedExportFile",
+	"NeedTypes",
+	"NeedSyntax",
+	"NeedTypesInfo",
+	"NeedTypesSizes",
+}
+
+func (mod LoadMode) String() string {
+	m := mod
+	if m == 0 {
+		return "LoadMode(0)"
+	}
+	var out []string
+	for i, x := range allModes {
+		if x > m {
+			break
+		}
+		if (m & x) != 0 {
+			out = append(out, modeStrings[i])
+			m = m ^ x
+		}
+	}
+	if m != 0 {
+		out = append(out, "Unknown")
+	}
+	return fmt.Sprintf("LoadMode(%s)", strings.Join(out, "|"))
+}

vendor/golang.org/x/tools/go/packages/visit.go

@@ -0,0 +1,59 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packages
+
+import (
+	"fmt"
+	"os"
+	"sort"
+)
+
+// Visit visits all the packages in the import graph whose roots are
+// pkgs, calling the optional pre function the first time each package
+// is encountered (preorder), and the optional post function after a
+// package's dependencies have been visited (postorder).
+// The boolean result of pre(pkg) determines whether
+// the imports of package pkg are visited.
+func Visit(pkgs []*Package, pre func(*Package) bool, post func(*Package)) {
+	seen := make(map[*Package]bool)
+	var visit func(*Package)
+	visit = func(pkg *Package) {
+		if !seen[pkg] {
+			seen[pkg] = true
+
+			if pre == nil || pre(pkg) {
+				paths := make([]string, 0, len(pkg.Imports))
+				for path := range pkg.Imports {
+					paths = append(paths, path)
+				}
+				sort.Strings(paths) // Imports is a map, this makes visit stable
+				for _, path := range paths {
+					visit(pkg.Imports[path])
+				}
+			}
+
+			if post != nil {
+				post(pkg)
+			}
+		}
+	}
+	for _, pkg := range pkgs {
+		visit(pkg)
+	}
+}
+
+// PrintErrors prints to os.Stderr the accumulated errors of all
+// packages in the import graph rooted at pkgs, dependencies first.
+// PrintErrors returns the number of errors printed.
+func PrintErrors(pkgs []*Package) int {
+	var n int
+	Visit(pkgs, nil, func(pkg *Package) {
+		for _, err := range pkg.Errors {
+			fmt.Fprintln(os.Stderr, err)
+			n++
+		}
+	})
+	return n
+}