cmd/go: make 'go get -t' consider test dependencies in module mode

Fixes #32037

Change-Id: I696fe2029e383746252f37fe8d30df71b5ac8a6c
Reviewed-on: https://go-review.googlesource.com/c/go/+/177677
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/alldocs.go

@@ -557,7 +557,7 @@
 //
 // Usage:
 //
-// 	go get [-d] [-m] [-u] [-v] [-insecure] [build flags] [packages]
+// 	go get [-d] [-m] [-t] [-u] [-v] [-insecure] [build flags] [packages]
 //
 // Get resolves and adds dependencies to the current development module
 // and then builds and installs them.
@@ -600,6 +600,9 @@
 // are competing requirements for a particular module, then 'go get' resolves
 // those requirements by taking the maximum requested version.)
 //
+// The -t flag instructs get to consider modules needed to build tests of
+// packages specified on the command line.
+//
 // The -u flag instructs get to update dependencies to use newer minor or
 // patch releases when available. Continuing the previous example,
 // 'go get -u A' will use the latest A with B v1.3.1 (not B v1.2.3).
@@ -610,6 +613,9 @@
 // 'go get -u=patch A@latest' will use the latest A with B v1.2.4 (not B v1.2.3),
 // while 'go get -u=patch A' will use a patch release of A instead.
 //
+// When the -t and -u flags are used together, get will update
+// test dependencies as well.
+//
 // In general, adding a new dependency may require upgrading
 // existing dependencies to keep a working build, and 'go get' does
 // this automatically. Similarly, downgrading one dependency may

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

@@ -31,7 +31,7 @@ import (
 var CmdGet = &base.Command{
 	// Note: -d -m -u are listed explicitly because they are the most common get flags.
 	// Do not send CLs removing them because they're covered by [get flags].
-	UsageLine: "go get [-d] [-m] [-u] [-v] [-insecure] [build flags] [packages]",
+	UsageLine: "go get [-d] [-m] [-t] [-u] [-v] [-insecure] [build flags] [packages]",
 	Short:     "add dependencies to current module and install them",
 	Long: `
 Get resolves and adds dependencies to the current development module
@@ -75,6 +75,9 @@ will use the latest A but then use B v1.2.3, as requested by A. (If there
 are competing requirements for a particular module, then 'go get' resolves
 those requirements by taking the maximum requested version.)
 
+The -t flag instructs get to consider modules needed to build tests of
+packages specified on the command line.
+
 The -u flag instructs get to update dependencies to use newer minor or
 patch releases when available. Continuing the previous example,
 'go get -u A' will use the latest A with B v1.3.1 (not B v1.2.3).
@@ -85,6 +88,9 @@ Continuing the previous example,
 'go get -u=patch A@latest' will use the latest A with B v1.2.4 (not B v1.2.3),
 while 'go get -u=patch A' will use a patch release of A instead.
 
+When the -t and -u flags are used together, get will update
+test dependencies as well.
+
 In general, adding a new dependency may require upgrading
 existing dependencies to keep a working build, and 'go get' does
 this automatically. Similarly, downgrading one dependency may
@@ -261,9 +267,7 @@ func runGet(cmd *base.Command, args []string) {
 	if *getFix {
 		fmt.Fprintf(os.Stderr, "go get: -fix flag is a no-op when using modules\n")
 	}
-	if *getT {
-		fmt.Fprintf(os.Stderr, "go get: -t flag is a no-op when using modules\n")
-	}
+	modload.LoadTests = *getT
 
 	if cfg.BuildMod == "vendor" {
 		base.Fatalf("go get: disabled by -mod=%s", cfg.BuildMod)
@@ -781,25 +785,26 @@ func newUpgrader(cmdline map[string]*query, pkgs map[string]bool) *upgrader {
 		// Initialize work queue with root packages.
 		seen := make(map[string]bool)
 		var work []string
-		for pkg := range pkgs {
-			seen[pkg] = true
-			for _, imp := range modload.PackageImports(pkg) {
-				if !pkgs[imp] && !seen[imp] {
-					seen[imp] = true
-					work = append(work, imp)
-				}
+		add := func(path string) {
+			if !seen[path] {
+				seen[path] = true
+				work = append(work, path)
 			}
 		}
+		for pkg := range pkgs {
+			add(pkg)
+		}
 		for len(work) > 0 {
 			pkg := work[0]
 			work = work[1:]
 			m := modload.PackageModule(pkg)
 			u.upgrade[m.Path] = true
-			for _, imp := range modload.PackageImports(pkg) {
-				if !seen[imp] {
-					seen[imp] = true
-					work = append(work, imp)
-				}
+			imports, testImports := modload.PackageImports(pkg)
+			for _, imp := range imports {
+				add(imp)
+			}
+			for _, imp := range testImports {
+				add(imp)
 			}
 		}
 	}

src/cmd/go/internal/modload/load.go

@@ -496,17 +496,26 @@ func PackageModule(path string) module.Version {
 }
 
 // PackageImports returns the imports for the package named by the import path.
-// It does not include test imports. It returns nil for unknown packages.
-func PackageImports(path string) []string {
+// Test imports will be returned as well if tests were loaded for the package
+// (i.e., if "all" was loaded or if LoadTests was set and the path was matched
+// by a command line argument). PackageImports will return nil for
+// unknown package paths.
+func PackageImports(path string) (imports, testImports []string) {
 	pkg, ok := loaded.pkgCache.Get(path).(*loadPkg)
 	if !ok {
-		return nil
+		return nil, nil
 	}
-	imports := make([]string, len(pkg.imports))
+	imports = make([]string, len(pkg.imports))
 	for i, p := range pkg.imports {
 		imports[i] = p.path
 	}
-	return imports
+	if pkg.test != nil {
+		testImports = make([]string, len(pkg.test.imports))
+		for i, p := range pkg.test.imports {
+			testImports[i] = p.path
+		}
+	}
+	return imports, testImports
 }
 
 // ModuleUsedDirectly reports whether the main module directly imports

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

@@ -0,0 +1,58 @@
+env GO111MODULE=on
+
+# By default, 'go get' should ignore tests
+cp go.mod.empty go.mod
+go get m/a
+! grep rsc.io/quote go.mod
+
+# 'go get -t' should consider test dependencies of the named package.
+cp go.mod.empty go.mod
+go get -d -t m/a
+grep 'rsc.io/quote v1.5.2$' go.mod
+
+# 'go get -t' should not consider test dependencies of imported packages,
+# including packages imported from tests.
+cp go.mod.empty go.mod
+go get -d -t m/b
+! grep rsc.io/quote go.mod
+
+# 'go get -t -u' should update test dependencies of the named package.
+cp go.mod.empty go.mod
+go mod edit -require=rsc.io/quote@v1.5.1
+go get -d -t -u m/a
+grep 'rsc.io/quote v1.5.2$' go.mod
+
+# 'go get -t -u' should not add or update test dependencies
+# of imported packages, including packages imported from tests.
+cp go.mod.empty go.mod
+go get -d -t -u m/b
+! grep rsc.io/quote go.mod
+go mod edit -require=rsc.io/quote@v1.5.1
+go get -d -t -u m/b
+grep 'rsc.io/quote v1.5.1$' go.mod
+
+# 'go get all' should consider test dependencies with or without -t.
+cp go.mod.empty go.mod
+go get all
+grep 'rsc.io/quote v1.5.2$' go.mod
+
+-- go.mod.empty --
+module m
+
+-- a/a.go --
+package a
+
+-- a/a_test.go --
+package a_test
+
+import _ "rsc.io/quote"
+
+-- b/b.go --
+package b
+
+import _ "m/a"
+
+-- b/b_test.go --
+package b_test
+
+import _ "m/a"