cmd/go/internal/modget: support the suffix '@patch' in 'go get'

As of this change, an explicit '@patch' suffix is to '-u=patch' as
'@latest' is to '-u'.

RELNOTE='go get' in module mode now supports the version suffix '@patch'.

Fixes #26812

Change-Id: Ib5eee40de640440f7470d37a574b311ef8a67f67
Reviewed-on: https://go-review.googlesource.com/c/go/+/167747
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/alldocs.go

@@ -558,8 +558,6 @@
 // For modules stored in source control repositories, the version suffix can
 // also be a commit hash, branch identifier, or other syntax known to the
 // source control system, as in 'go get golang.org/x/text@master'.
-// The version suffix @latest explicitly requests the default behavior
-// described above.
 //
 // If a module under consideration is already a dependency of the current
 // development module, then get will update the required version.
@@ -568,6 +566,13 @@
 // dependency should be removed entirely, downgrading or removing modules
 // depending on it as needed.
 //
+// The version suffix @latest explicitly requests the latest minor release of the
+// given path.
+//
+// The suffix @patch requests the latest patch release: if the path is already in
+// the build list, the selected version will have the same minor version.
+// If the path is not already in the build list, @patch is equivalent to @latest.
+//
 // Although get defaults to using the latest version of the module containing
 // a named package, it does not use the latest version of that module's
 // dependencies. Instead it prefers to use the specific dependency versions
@@ -581,9 +586,11 @@
 // 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).
 //
-// The -u=patch flag (not -u patch) instructs get to update dependencies
-// to use newer patch releases when available. Continuing the previous example,
-// 'go get -u=patch A' will use the latest A with B v1.2.4 (not B v1.2.3).
+// The -u=patch flag (not -u patch) also instructs get to update dependencies,
+// but changes the default to select patch releases.
+// 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.
 //
 // In general, adding a new dependency may require upgrading
 // existing dependencies to keep a working build, and 'go get' does

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

@@ -339,7 +339,7 @@ func loadAll(testAll bool) []string {
 	if !testAll {
 		loaded.testRoots = true
 	}
-	all := TargetPackages()
+	all := TargetPackages("...")
 	loaded.load(func() []string { return all })
 	WriteGoMod()
 
@@ -357,10 +357,11 @@ func loadAll(testAll bool) []string {
 // Only "ignore" and malformed build tag requirements are considered false.
 var anyTags = map[string]bool{"*": true}
 
-// TargetPackages returns the list of packages in the target (top-level) module,
-// under all build tag settings.
-func TargetPackages() []string {
-	return matchPackages("...", anyTags, false, []module.Version{Target})
+// TargetPackages returns the list of packages in the target (top-level) module
+// matching pattern, which may be relative to the working directory, under all
+// build tag settings.
+func TargetPackages(pattern string) []string {
+	return matchPackages(pattern, anyTags, false, []module.Version{Target})
 }
 
 // BuildList returns the module build list,

src/cmd/go/testdata/mod/patch.example.com_depofdirectpatch_v1.0.0.txt

+patch.example.com/depofdirectpatch v1.0.0
+written by hand
+
+-- .mod --
+module patch.example.com/depofdirectpatch
+-- .info --
+{"Version":"v1.0.0"}
+-- go.mod --
+module patch.example.com/depofdirectpatch
+-- depofdirectpatch.go --
+package depofdirectpatch

src/cmd/go/testdata/mod/patch.example.com_depofdirectpatch_v1.0.1.txt

+patch.example.com/depofdirectpatch v1.0.1
+written by hand
+
+-- .mod --
+module patch.example.com/depofdirectpatch
+-- .info --
+{"Version":"v1.0.1"}
+-- go.mod --
+module patch.example.com/depofdirectpatch
+-- depofdirectpatch.go --
+package depofdirectpatch

src/cmd/go/testdata/mod/patch.example.com_direct_v1.0.0.txt

+patch.example.com/direct v1.0.0
+written by hand
+
+-- .mod --
+module patch.example.com/direct
+
+require (
+	patch.example.com/indirect v1.0.0
+)
+-- .info --
+{"Version":"v1.0.0"}
+-- go.mod --
+module patch.example.com/direct
+
+require (
+	patch.example.com/indirect v1.0.0
+)
+-- direct.go --
+package direct
+
+import _ "patch.example.com/indirect"

src/cmd/go/testdata/mod/patch.example.com_direct_v1.0.1.txt

+patch.example.com/direct v1.0.1
+written by hand
+
+-- .mod --
+module patch.example.com/direct
+
+require (
+	patch.example.com/indirect v1.0.0
+	patch.example.com/depofdirectpatch v1.0.0
+)
+-- .info --
+{"Version":"v1.0.1"}
+-- go.mod --
+module patch.example.com/direct
+
+require (
+	patch.example.com/indirect v1.0.0
+	patch.example.com/depofdirectpatch v1.0.0
+)
+-- direct.go --
+package direct
+
+import _ "patch.example.com/indirect"
+-- usedepofdirectpatch/unused.go --
+package usedepofdirectpatch
+
+import _ "patch.example.com/depofdirectpatch"

src/cmd/go/testdata/mod/patch.example.com_direct_v1.1.0.txt

+patch.example.com/direct v1.1.0
+written by hand
+
+-- .mod --
+module patch.example.com/direct
+
+require (
+	patch.example.com/indirect v1.0.0
+)
+-- .info --
+{"Version":"v1.1.0"}
+-- go.mod --
+module patch.example.com/direct
+
+require (
+	patch.example.com/indirect v1.0.0
+)
+-- direct.go --
+package direct
+
+import _ "patch.example.com/indirect"

src/cmd/go/testdata/mod/patch.example.com_indirect_v1.0.0.txt

+patch.example.com/indirect v1.0.0
+written by hand
+
+-- .mod --
+module patch.example.com/indirect
+-- .info --
+{"Version":"v1.0.0"}
+-- go.mod --
+module patch.example.com/indirect
+-- direct.go --
+package indirect

src/cmd/go/testdata/mod/patch.example.com_indirect_v1.0.1.txt

+patch.example.com/indirect v1.0.1
+written by hand
+
+-- .mod --
+module patch.example.com/indirect
+-- .info --
+{"Version":"v1.0.1"}
+-- go.mod --
+module patch.example.com/indirect
+-- direct.go --
+package indirect

src/cmd/go/testdata/mod/patch.example.com_indirect_v1.1.0.txt

+patch.example.com/indirect v1.1.0
+written by hand
+
+-- .mod --
+module patch.example.com/indirect
+-- .info --
+{"Version":"v1.1.0"}
+-- go.mod --
+module patch.example.com/indirect
+-- direct.go --
+package indirect

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

-env GO111MODULE=on
-
-go list -m all
-stdout '^rsc.io/quote v1.4.0'
-stdout '^rsc.io/sampler v1.0.0'
-
-# get -u=patch rsc.io/quote should take latest quote & patch update its deps
-go get -m -u=patch rsc.io/quote
-go list -m all
-stdout '^rsc.io/quote v1.5.2'
-stdout '^rsc.io/sampler v1.3.1'
-stdout '^golang.org/x/text v0.0.0-'
-
-# get -u=patch quote@v1.2.0 should take that version of quote & patch update its deps
-go get -m -u=patch rsc.io/quote@v1.2.0
-go list -m all
-stdout '^rsc.io/quote v1.2.0'
-stdout '^rsc.io/sampler v1.3.1'
-stdout '^golang.org/x/text v0.0.0-'
-
-# get -u=patch with no args applies to all deps
-go get -m -u=patch
-go list -m all
-stdout '^rsc.io/quote v1.2.1'
-
--- go.mod --
-module x
-require rsc.io/quote v1.4.0
-

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

+env GO111MODULE=on
+
+# Initially, we are at v1.0.0 for all dependencies.
+cp go.mod go.mod.orig
+go list -m all
+stdout '^patch.example.com/direct v1.0.0'
+stdout '^patch.example.com/indirect v1.0.0'
+! stdout '^patch.example.com/depofdirectpatch'
+
+# get -m -u=patch, with no arguments, should patch-update all dependencies,
+# pulling in transitive dependencies and also patching those.
+#
+# TODO(golang.org/issue/26902): We should not update transitive dependencies
+# that don't affect the transitive import graph of the main module in any way.
+cp go.mod.orig go.mod
+go get -m -u=patch
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.0.1'
+stdout '^patch.example.com/depofdirectpatch v1.0.1' # TODO: leave at v1.0.0
+
+# 'get -m all@patch' should be equivalent to 'get -u=patch -m all'
+cp go.mod.orig go.mod
+go get -m all@patch
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.0.1'
+stdout '^patch.example.com/depofdirectpatch v1.0.0'
+
+# Requesting the direct dependency with -u=patch but without an explicit version
+# should patch-update it and its dependencies.
+cp go.mod.orig go.mod
+go get -m -u=patch patch.example.com/direct
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.0.1'
+stdout '^patch.example.com/depofdirectpatch v1.0.1' # TODO: leave at v1.0.0
+
+# Requesting only the indirect dependency should not update the direct one.
+cp go.mod.orig go.mod
+go get -m -u=patch patch.example.com/indirect
+go list -m all
+stdout '^patch.example.com/direct v1.0.0'
+stdout '^patch.example.com/indirect v1.0.1'
+! stdout '^patch.example.com/depofdirectpatch'
+
+# @patch should apply only to the specific module.
+# but the result must reflect its upgraded requirements.
+cp go.mod.orig go.mod
+go get -m patch.example.com/direct@patch
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.0.0'
+stdout '^patch.example.com/depofdirectpatch v1.0.0'
+
+# An explicit @patch should override a general -u.
+cp go.mod.orig go.mod
+go get -m -u patch.example.com/direct@patch
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.1.0'
+stdout '^patch.example.com/depofdirectpatch v1.0.1'
+
+# An explicit @latest should override a general -u=patch.
+cp go.mod.orig go.mod
+go get -m -u=patch patch.example.com/direct@latest
+go list -m all
+stdout '^patch.example.com/direct v1.1.0'
+stdout '^patch.example.com/indirect v1.0.1'
+! stdout '^patch.example.com/depofdirectpatch'
+
+# Standard-library modules cannot be upgraded explicitly.
+cp go.mod.orig go.mod
+! go get -m std@patch
+stderr 'explicit requirement on standard-library module std not allowed'
+
+
+-- go.mod --
+module x
+
+require patch.example.com/direct v1.0.0
+
+-- main.go --
+package x
+import _ "patch.example.com/direct"

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

+env GO111MODULE=on
+
+# Initially, we are at v1.0.0 for all dependencies.
+cp go.mod go.mod.orig
+go list -m all
+stdout '^patch.example.com/direct v1.0.0'
+stdout '^patch.example.com/indirect v1.0.0'
+! stdout '^patch.example.com/depofdirectpatch'
+
+# get -u=patch, with no arguments, should patch-update all dependencies,
+# pulling in transitive dependencies and also patching those.
+#
+# TODO(golang.org/issue/26902): We should not update dependencies
+# that don't affect the transitive import graph of the main module in any way.
+cp go.mod.orig go.mod
+go get -u=patch
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.0.1'
+stdout '^patch.example.com/depofdirectpatch v1.0.1' # TODO: leave at v1.0.0
+
+# 'get all@patch' should be equivalent to 'get -u=patch all'
+cp go.mod.orig go.mod
+go get all@patch
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.0.1'
+stdout '^patch.example.com/depofdirectpatch v1.0.0'
+
+# Requesting the direct dependency with -u=patch but without an explicit version
+# should patch-update it and its dependencies.
+cp go.mod.orig go.mod
+go get -u=patch patch.example.com/direct
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.0.1'
+stdout '^patch.example.com/depofdirectpatch v1.0.1' # TODO: leave at v1.0.0
+
+# Requesting only the indirect dependency should not update the direct one.
+cp go.mod.orig go.mod
+go get -u=patch patch.example.com/indirect
+go list -m all
+stdout '^patch.example.com/direct v1.0.0'
+stdout '^patch.example.com/indirect v1.0.1'
+! stdout '^patch.example.com/depofdirectpatch'
+
+# @patch should apply only to the specific module,
+# but the result must reflect its upgraded requirements.
+cp go.mod.orig go.mod
+go get patch.example.com/direct@patch
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.0.0'
+stdout '^patch.example.com/depofdirectpatch v1.0.0'
+
+# An explicit @patch should override a general -u.
+cp go.mod.orig go.mod
+go get -u patch.example.com/direct@patch
+go list -m all
+stdout '^patch.example.com/direct v1.0.1'
+stdout '^patch.example.com/indirect v1.1.0'
+stdout '^patch.example.com/depofdirectpatch v1.0.1'
+
+# An explicit @latest should override a general -u=patch.
+cp go.mod.orig go.mod
+go get -u=patch patch.example.com/direct@latest
+go list -m all
+stdout '^patch.example.com/direct v1.1.0'
+stdout '^patch.example.com/indirect v1.0.1'
+! stdout '^patch.example.com/depofdirectpatch'
+
+# Standard-library packages cannot be upgraded explicitly.
+cp go.mod.orig go.mod
+! go get cmd/vet@patch
+stderr 'cannot use pattern .* with explicit version'
+
+# However, standard-library packages without explicit versions are fine.
+go get -u=patch -d cmd/get
+
+
+-- go.mod --
+module x
+
+require patch.example.com/direct v1.0.0
+
+-- main.go --
+package x
+import _ "patch.example.com/direct"