cmd/go: fix error for empty packages referenced with relative paths

'go build' now reports a more useful error when a relative path on the
command line points to a directory that doesn't exist or a directory
without .go files. Errors are generated by go/build.Context.ImportDir
instead of a vague call to base.Fatalf in modload.

Fixes #35414

Change-Id: I2642230c5e409107b98bb6d6c3a484d8d25b4147
Reviewed-on: https://go-review.googlesource.com/c/go/+/206902
Run-TryBot: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 6a6f77e3673d7a074c5ebfed20c79e0bdc84235e..8fc33e35fa9a2a8407a5597adfd78058d4f05659 100644 (file)
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -670,6 +670,11 @@ func loadPackageData(path, parentPath, parentDir, parentRoot string, parentIsStd
        // we create from the full directory to the package.
        // Otherwise it is the usual import path.
        // For vendored imports, it is the expanded form.
+       //
+       // Note that when modules are enabled, local import paths are normally
+       // canonicalized by modload.ImportPaths before now. However, if there's an
+       // error resolving a local path, it will be returned untransformed
+       // so that 'go list -e' reports something useful.
        importKey := importSpec{
                path:        path,
                parentPath:  parentPath,

diff --git a/src/cmd/go/internal/modload/build.go b/src/cmd/go/internal/modload/build.go
index 352ec73758dfa408209a0acf4d4151ebaf4fa413..5a281a9304da28259249b3f60c8eb7bfd1684b73 100644 (file)
--- a/src/cmd/go/internal/modload/build.go
+++ b/src/cmd/go/internal/modload/build.go
@@ -45,11 +45,19 @@ func findStandardImportPath(path string) string {
        return ""
 }
 
+// PackageModuleInfo returns information about the module that provides
+// a given package. If modules are not enabled or if the package is in the
+// standard library or if the package was not successfully loaded with
+// ImportPaths or a similar loading function, nil is returned.
 func PackageModuleInfo(pkgpath string) *modinfo.ModulePublic {
        if isStandardImportPath(pkgpath) || !Enabled() {
                return nil
        }
-       return moduleInfo(findModule(pkgpath, pkgpath), true)
+       m, ok := findModule(pkgpath)
+       if !ok {
+               return nil
+       }
+       return moduleInfo(m, true)
 }
 
 func ModuleInfo(path string) *modinfo.ModulePublic {
@@ -199,12 +207,11 @@ func PackageBuildInfo(path string, deps []string) string {
        if isStandardImportPath(path) || !Enabled() {
                return ""
        }
-
-       target := findModule(path, path)
+       target := mustFindModule(path, path)
        mdeps := make(map[module.Version]bool)
        for _, dep := range deps {
                if !isStandardImportPath(dep) {
-                       mdeps[findModule(path, dep)] = true
+                       mdeps[mustFindModule(path, dep)] = true
                }
        }
        var mods []module.Version
@@ -239,9 +246,12 @@ func PackageBuildInfo(path string, deps []string) string {
        return buf.String()
 }
 
-// findModule returns the module containing the package at path,
-// needed to build the package at target.
-func findModule(target, path string) module.Version {
+// mustFindModule is like findModule, but it calls base.Fatalf if the
+// module can't be found.
+//
+// TODO(jayconrod): remove this. Callers should use findModule and return
+// errors instead of relying on base.Fatalf.
+func mustFindModule(target, path string) module.Version {
        pkg, ok := loaded.pkgCache.Get(path).(*loadPkg)
        if ok {
                if pkg.err != nil {
@@ -261,6 +271,20 @@ func findModule(target, path string) module.Version {
        panic("unreachable")
 }
 
+// findModule searches for the module that contains the package at path.
+// If the package was loaded with ImportPaths or one of the other loading
+// functions, its containing module and true are returned. Otherwise,
+// module.Version{} and false are returend.
+func findModule(path string) (module.Version, bool) {
+       if pkg, ok := loaded.pkgCache.Get(path).(*loadPkg); ok {
+               return pkg.mod, pkg.mod != module.Version{}
+       }
+       if path == "command-line-arguments" {
+               return Target, true
+       }
+       return module.Version{}, false
+}
+
 func ModInfoProg(info string, isgccgo bool) []byte {
        // Inject a variable with the debug information as runtime.modinfo,
        // but compile it in package main so that it is specific to the binary.

diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index ca6c260f45dbebefd617f814d165f86ef21d2daf..2df7bd04b7a7baf47417f2226e4ba927e8392d2f 100644 (file)
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -94,11 +94,11 @@ func ImportPathsQuiet(patterns []string, tags map[string]bool) []*search.Match {
                                pkgs := m.Pkgs
                                m.Pkgs = m.Pkgs[:0]
                                for _, pkg := range pkgs {
-                                       dir := pkg
-                                       if !filepath.IsAbs(dir) {
+                                       var dir string
+                                       if !filepath.IsAbs(pkg) {
                                                dir = filepath.Join(base.Cwd, pkg)
                                        } else {
-                                               dir = filepath.Clean(dir)
+                                               dir = filepath.Clean(pkg)
                                        }
 
                                        // golang.org/issue/32917: We should resolve a relative path to a

diff --git a/src/cmd/go/testdata/script/mod_empty_err.txt b/src/cmd/go/testdata/script/mod_empty_err.txt
new file mode 100644 (file)
index 0000000..729f848
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_empty_err.txt
@@ -0,0 +1,36 @@
+# This test checks error messages for non-existant packages in module mode.
+# Veries golang.org/issue/35414
+env GO111MODULE=on
+cd $WORK
+
+go list -e -f {{.Error}} .
+stdout 'package \.: no Go files in \$WORK'
+
+go list -e -f {{.Error}} ./empty
+stdout 'package \./empty: no Go files in \$WORK[/\\]empty'
+
+go list -e -f {{.Error}} ./exclude
+stdout 'package \./exclude: build constraints exclude all Go files in \$WORK[/\\]exclude'
+
+go list -e -f {{.Error}} ./missing
+stdout 'package \./missing: cannot find package "." in:\s*\$WORK[/\\]missing'
+
+# use 'go build -n' because 'go list' reports no error.
+! go build -n ./testonly
+stderr 'example.com/m/testonly: no non-test Go files in \$WORK[/\\]testonly'
+
+-- $WORK/go.mod --
+module example.com/m
+
+go 1.14
+
+-- $WORK/empty/empty.txt --
+-- $WORK/exclude/exclude.go --
+// +build exclude
+
+package exclude
+-- $WORK/testonly/testonly_test.go --
+package testonly_test
+-- $WORK/excluded-stdout --
+package ./excluded: cannot find package "." in:
+       $WORK/excluded