Merge GoLibrary and GoSource providers (#4030)

**What type of PR is this?**
Code simplification

**What does this PR do? Why is it needed?**
These providers are 1:1, and we always create a library followed by
`source_from_library`. Merging them allows to remove the `library` field
from `GoSource` as well as the the `resolve` field, since we don't need
to smuggle the closure between the providers anymore.

If we do this, we will also need to fix up Gazelle. We can either have a
patch in this repo so CI passes and then followup with the Gazelle fix,
or somehow shim the API until we release new versions in lockstep. Open
to ideas how to best do this.

**Which issues(s) does this PR fix?**
One step toward #2578

Fixes #

**Other notes for review**

docs/go/core/rules.bzl

@@ -3,9 +3,8 @@
   [Bourne shell tokenization]: https://docs.bazel.build/versions/master/be/common-definitions.html#sh-tokenization
   [Gazelle]: https://github.com/bazelbuild/bazel-gazelle
   [GoArchive]: /go/providers.rst#GoArchive
-  [GoLibrary]: /go/providers.rst#GoLibrary
   [GoPath]: /go/providers.rst#GoPath
-  [GoSource]: /go/providers.rst#GoSource
+  [GoInfo]: /go/providers.rst#GoInfo
   [build constraints]: https://golang.org/pkg/go/build/#hdr-Build_Constraints
   [cc_library deps]: https://docs.bazel.build/versions/master/be/c-cpp.html#cc_library.deps
   [cgo]: http://golang.org/cmd/cgo/
@@ -51,9 +50,8 @@ sufficient to match the capabilities of the normal go tools.
 - [Bourne shell tokenization]
 - [Gazelle]
 - [GoArchive]
-- [GoLibrary]
 - [GoPath]
-- [GoSource]
+- [GoInfo]
 - [build constraints]:
 - [cc_library deps]
 - [cgo]

extras/gomock.bzl

@@ -25,7 +25,7 @@
 load("@bazel_skylib//lib:paths.bzl", "paths")
 load("//go/private:common.bzl", "GO_TOOLCHAIN", "GO_TOOLCHAIN_LABEL")
 load("//go/private:context.bzl", "go_context")
-load("//go/private:providers.bzl", "GoLibrary")
+load("//go/private:providers.bzl", "GoInfo")
 load("//go/private/rules:wrappers.bzl", go_binary = "go_binary_macro")
 
 _MOCKGEN_TOOL = Label("//extras/gomock:mockgen")
@@ -36,10 +36,10 @@ def _gomock_source_impl(ctx):
 
     # In Source mode, it's not necessary to pass through a library, as the only thing we use it for is setting up
     # the relative file locations. Forcing users to pass a library makes it difficult in the case where a mock should
-    # be included as part of that same library, as it results in a dependency loop (GoMock -> GoLibrary -> GoMock).
+    # be included as part of that same library, as it results in a dependency loop (GoMock -> GoInfo -> GoMock).
     # Allowing users to pass an importpath directly bypasses this issue.
     # See the test case in //tests/extras/gomock/source_with_importpath for an example.
-    importpath = ctx.attr.source_importpath if ctx.attr.source_importpath else ctx.attr.library[GoLibrary].importmap
+    importpath = ctx.attr.source_importpath if ctx.attr.source_importpath else ctx.attr.library[GoInfo].importmap
 
     # create GOPATH and copy source into GOPATH
     go_path_prefix = "gopath"
@@ -113,7 +113,7 @@ _gomock_source = rule(
     attrs = {
         "library": attr.label(
             doc = "The target the Go library where this source file belongs",
-            providers = [GoLibrary],
+            providers = [GoInfo],
             mandatory = False,
         ),
         "source_importpath": attr.string(
@@ -257,7 +257,7 @@ def _gomock_reflect(name, library, out, mockgen_tool, **kwargs):
 
 def _gomock_prog_gen_impl(ctx):
     args = ["-prog_only"]
-    args.append(ctx.attr.library[GoLibrary].importpath)
+    args.append(ctx.attr.library[GoInfo].importpath)
     args.append(",".join(ctx.attr.interfaces))
 
     cmd = ctx.file.mockgen_tool
@@ -280,7 +280,7 @@ _gomock_prog_gen = rule(
     attrs = {
         "library": attr.label(
             doc = "The target the Go library is at to look for the interfaces in. When this is set and source is not set, mockgen will use its reflect code to generate the mocks. If source is set, its dependencies will be included in the GOPATH that mockgen will be run in.",
-            providers = [GoLibrary],
+            providers = [GoInfo],
             mandatory = True,
         ),
         "out": attr.output(
@@ -313,7 +313,7 @@ def _gomock_prog_exec_impl(ctx):
 
     # annoyingly, the interfaces join has to go after the importpath so we can't
     # share those.
-    args.append(ctx.attr.library[GoLibrary].importpath)
+    args.append(ctx.attr.library[GoInfo].importpath)
     args.append(",".join(ctx.attr.interfaces))
 
     ctx.actions.run_shell(
@@ -337,7 +337,7 @@ _gomock_prog_exec = rule(
     attrs = {
         "library": attr.label(
             doc = "The target the Go library is at to look for the interfaces in. When this is set and source is not set, mockgen will use its reflect code to generate the mocks. If source is set, its dependencies will be included in the GOPATH that mockgen will be run in.",
-            providers = [GoLibrary],
+            providers = [GoInfo],
             mandatory = True,
         ),
         "out": attr.output(

go/core.rst

@@ -5,9 +5,8 @@ Core Go rules
 .. _Bourne shell tokenization: https://docs.bazel.build/versions/master/be/common-definitions.html#sh-tokenization
 .. _Gazelle: https://github.com/bazelbuild/bazel-gazelle
 .. _GoArchive: providers.rst#GoArchive
-.. _GoLibrary: providers.rst#GoLibrary
 .. _GoPath: providers.rst#GoPath
-.. _GoSource: providers.rst#GoSource
+.. _GoInfo: providers.rst#GoInfo
 .. _build constraints: https://golang.org/pkg/go/build/#hdr-Build_Constraints
 .. _cc_library deps: https://docs.bazel.build/versions/master/be/c-cpp.html#cc_library.deps
 .. _cgo: http://golang.org/cmd/cgo/

go/def.bzl

@@ -29,6 +29,7 @@ load(
 load(
     "//go/private:context.bzl",
     _go_context = "go_context",
+    _new_go_info = "new_go_info",
 )
 load(
     "//go/private:go_toolchain.bzl",
@@ -38,10 +39,9 @@ load(
     "//go/private:providers.bzl",
     _GoArchive = "GoArchive",
     _GoArchiveData = "GoArchiveData",
-    _GoLibrary = "GoLibrary",
+    _GoInfo = "GoInfo",
     _GoPath = "GoPath",
     _GoSDK = "GoSDK",
-    _GoSource = "GoSource",
 )
 load(
     "//go/private/rules:cross.bzl",
@@ -134,11 +134,19 @@ go_tool_library = _go_tool_library
 go_toolchain = _go_toolchain
 nogo = _nogo
 
-# See go/providers.rst#GoLibrary for full documentation.
-GoLibrary = _GoLibrary
+# This provider is deprecated and will be removed in a future release.
+# Use GoInfo instead.
+GoLibrary = _GoInfo
 
-# See go/providers.rst#GoSource for full documentation.
-GoSource = _GoSource
+# This provider is deprecated and will be removed in a future release.
+# Use GoInfo instead.
+GoSource = _GoInfo
+
+# See go/providers.rst#GoInfo for full documentation.
+GoInfo = _GoInfo
+
+# See go/toolchains.rst#new_go_info for full documentation.
+new_go_info = _new_go_info
 
 # See go/providers.rst#GoPath for full documentation.
 GoPath = _GoPath

go/nogo.rst

@@ -8,8 +8,7 @@
 .. _go_library: /docs/go/core/rules.md#go_library
 .. _analysis: https://godoc.org/golang.org/x/tools/go/analysis
 .. _Analyzer: https://godoc.org/golang.org/x/tools/go/analysis#Analyzer
-.. _GoLibrary: providers.rst#GoLibrary
-.. _GoSource: providers.rst#GoSource
+.. _GoInfo: providers.rst#GoInfo
 .. _GoArchive: providers.rst#GoArchive
 .. _vet: https://golang.org/cmd/vet/
 .. _golangci-lint: https://github.com/golangci/golangci-lint

go/private/actions/archive.bzl

@@ -43,7 +43,7 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
     if source == None:
         fail("source is a required parameter")
 
-    testfilter = getattr(source.library, "testfilter", None)
+    testfilter = getattr(source, "testfilter", None)
     pre_ext = ""
     if go.mode.linkmode == LINKMODE_C_ARCHIVE:
         pre_ext = "_"  # avoid collision with go_binary output file with .a extension
@@ -53,17 +53,17 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
         pre_ext = ".external"
     if _recompile_suffix:
         pre_ext += _recompile_suffix
-    out_lib = go.declare_file(go, name = source.library.name, ext = pre_ext + ".a")
+    out_lib = go.declare_file(go, name = source.name, ext = pre_ext + ".a")
 
     # store export information for compiling dependent packages separately
-    out_export = go.declare_file(go, name = source.library.name, ext = pre_ext + ".x")
+    out_export = go.declare_file(go, name = source.name, ext = pre_ext + ".x")
     out_cgo_export_h = None  # set if cgo used in c-shared or c-archive mode
 
     nogo = get_nogo(go)
     if nogo:
-        out_facts = go.declare_file(go, name = source.library.name, ext = pre_ext + ".facts")
-        out_nogo_log = go.declare_file(go, name = source.library.name, ext = pre_ext + ".nogo.log")
-        out_nogo_validation = go.declare_file(go, name = source.library.name, ext = pre_ext + ".nogo")
+        out_facts = go.declare_file(go, name = source.name, ext = pre_ext + ".facts")
+        out_nogo_log = go.declare_file(go, name = source.name, ext = pre_ext + ".nogo.log")
+        out_nogo_validation = go.declare_file(go, name = source.name, ext = pre_ext + ".nogo")
     else:
         out_facts = None
         out_nogo_log = None
@@ -78,8 +78,8 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
             fail("Archive mode does not match {} is {} expected {}".format(a.data.label, mode_string(a.source.mode), mode_string(go.mode)))
     runfiles = source.runfiles.merge_all(files)
 
-    importmap = "main" if source.library.is_main else source.library.importmap
-    importpath, _ = effective_importpath_pkgpath(source.library)
+    importmap = "main" if source.is_main else source.importmap
+    importpath, _ = effective_importpath_pkgpath(source)
 
     if source.cgo and not go.mode.pure:
         # TODO(jayconrod): do we need to do full Bourne tokenization here?
@@ -157,15 +157,13 @@ def emit_archive(go, source = None, _recompile_suffix = "", recompile_internal_d
         # may be mutable. For now, new copied fields are private (named with
         # a leading underscore) since they may change in the future.
 
-        # GoLibrary fields
-        name = source.library.name,
-        label = source.library.label,
-        importpath = source.library.importpath,
-        importmap = source.library.importmap,
-        importpath_aliases = source.library.importpath_aliases,
-        pathtype = source.library.pathtype,
-
-        # GoSource fields
+        # GoInfo fields
+        name = source.name,
+        label = source.label,
+        importpath = source.importpath,
+        importmap = source.importmap,
+        importpath_aliases = source.importpath_aliases,
+        pathtype = source.pathtype,
         srcs = tuple(source.srcs),
         _cover = source.cover,
         _embedsrcs = tuple(source.embedsrcs),

go/private/actions/stdlib.bzl

@@ -18,6 +18,10 @@ load(
     "GO_TOOLCHAIN_LABEL",
     "SUPPORTS_PATH_MAPPING_REQUIREMENT",
 )
+load(
+    "//go/private:context.bzl",
+    "new_go_info",
+)
 load(
     "//go/private:mode.bzl",
     "LINKMODE_NORMAL",
@@ -38,12 +42,11 @@ def emit_stdlib(go):
     Otherwise, the standard library will be compiled for the target.
 
     Returns:
-        A list of providers containing GoLibrary, GoSource and GoStdLib.
+        A list of providers containing GoInfo and GoStdLib.
     """
-    library = go.new_library(go)
-    source = go.library_to_source(go, {}, library, False)
+    go_info = new_go_info(go, {}, coverage_instrumented = False)
     stdlib = _sdk_stdlib(go) if _should_use_sdk_stdlib(go) else _build_stdlib(go)
-    return [source, library, stdlib]
+    return [go_info, stdlib]
 
 def _should_use_sdk_stdlib(go):
     version = parse_version(go.sdk.version)