cmd/go: fix listing of ambiguous paths

src/cmd/go/internal/load/pkg.go

@@ -1950,9 +1950,14 @@ func Packages(args []string) []*Package {
 // cannot be loaded at all.
 // The packages that fail to load will have p.Error != nil.
 func PackagesAndErrors(patterns []string) []*Package {
-	if len(patterns) > 0 {
-		for _, p := range patterns {
-			if strings.HasSuffix(p, ".go") {
+	for _, p := range patterns {
+		// Listing is only supported with all patterns referring to either:
+		// - Files that are part of the same directory.
+		// - Explicit package paths or patterns.
+		if strings.HasSuffix(p, ".go") {
+			// We need to test whether the path is an actual Go file and not a
+			// package path or pattern ending in '.go' (see golang.org/issue/34653).
+			if fi, err := os.Stat(p); err == nil && !fi.IsDir() {
 				return []*Package{GoFilesPackage(patterns)}
 			}
 		}

src/cmd/go/internal/modget/get.go

@@ -678,15 +678,6 @@ func runGet(cmd *base.Command, args []string) {
 	if *getD || len(pkgPatterns) == 0 {
 		return
 	}
-	// TODO(golang.org/issue/32483): handle paths ending with ".go" consistently
-	// with 'go build'. When we load packages above, we interpret arguments as
-	// package patterns, not source files. To preserve that interpretation here,
-	// we add a trailing slash to any patterns ending with ".go".
-	for i := range pkgPatterns {
-		if strings.HasSuffix(pkgPatterns[i], ".go") {
-			pkgPatterns[i] += "/"
-		}
-	}
 	work.BuildInit()
 	pkgs := load.PackagesForBuild(pkgPatterns)
 	work.InstallPackages(pkgPatterns, pkgs)

src/cmd/go/testdata/script/list_ambiguous_path.txt

@@ -0,0 +1,37 @@
+# Ensures that we can correctly list package patterns ending in '.go'.
+# See golang.org/issue/34653.
+
+# A single pattern for a package ending in '.go'.
+go list ./foo.go
+stdout '^test/foo.go$'
+
+# Multiple patterns for packages including one ending in '.go'.
+go list ./bar ./foo.go
+stdout '^test/bar$'
+stdout '^test/foo.go$'
+
+# A single pattern for a Go file.
+go list ./a.go
+stdout '^command-line-arguments$'
+
+# A single typo-ed pattern for a Go file. This should
+# treat the wrong pattern as if it were a package.
+! go list ./foo.go/b.go
+stderr 'package ./foo.go/b.go: cannot find package "."'
+
+# Multiple patterns for Go files with a typo. This should
+# treat the wrong pattern as if it were a non-existint file.
+! go list ./foo.go/a.go ./foo.go/b.go
+[windows] stderr './foo.go/b.go: The system cannot find the file specified'
+[!windows] stderr './foo.go/b.go: no such file or directory'
+
+-- a.go --
+package main
+-- bar/a.go --
+package bar
+-- foo.go/a.go --
+package foo.go
+-- go.mod --
+module "test"
+
+go 1.13

src/cmd/go/testdata/script/mod_get_trailing_slash.txt

@@ -1,8 +1,9 @@
-# go list should fail to load a package ending with ".go" since that denotes
-# a source file. However, ".go/" should work.
-# TODO(golang.org/issue/32483): perhaps we should treat non-existent paths
-# with .go suffixes as package paths instead.
-! go list example.com/dotgo.go
+# go list should succeed to load a package ending with ".go" if the path does
+# not correspond to an existing local file. Listing a pattern ending with
+# ".go/" should try to list a package regardless of whether a file exists at the
+# path without the suffixed "/" or not.
+go list example.com/dotgo.go
+stdout ^example.com/dotgo.go$
 go list example.com/dotgo.go/
 stdout ^example.com/dotgo.go$
 
@@ -15,9 +16,6 @@ go get -d example.com/[email protected]
 go get -d example.com/dotgo.go/@v1.0.0
 
 # go get (without -d) should also succeed in either case.
-# TODO(golang.org/issue/32483): we should be consistent with 'go build',
-# 'go list', and other commands. 'go list example.com/dotgo.go' (above) and
-# 'go get example.com/dotgo.go' should both succeed or both fail.
 [short] skip
 go get example.com/dotgo.go
 go get example.com/dotgo.go/