support c_shared mode

Summary:
Split from D29875545: This add c_shared and c_archive mode which produces either .so or .a file instead of binary.

The code is ported to the modern buck.

Reviewed By: lebentle

fbshipit-source-id: bb7cee0ed586f463d93f8335dcb32e532bb10ad8

Author: yottatsa

docs/__go_common.soy

@@ -137,7 +137,7 @@ Buck currently supports Go version 1.10.
   {param default: '[]' /}
   {param desc}
   Extra external linker flags passed to go link via <code>-extld</code> argument.
-  If argument is non-empty or <code>cgo_library</code> is used, the link mode 
+  If argument is non-empty or <code>cgo_library</code> is used, the link mode
   will switch to <code>external</code>.
   {/param}
 {/call}

docs/__table_of_contents.soy

@@ -76,6 +76,8 @@
             'go_library',
             'go_test',
             'cgo_library',
+            'go_exported_library',
+            'prebuilt_go_library',
         ],
         'groovy': [
             'groovy_library',

docs/rule/go_exported_library.soy

@@ -0,0 +1,135 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+{namespace go_exported_library}
+
+/***/
+{template .soyweb}
+  {call buck.page}
+    {param title: 'go_exported_library()' /}
+    {param navid: 'rule_go_exported_library' /}
+    {param prettify: true /}
+    {param description}
+      A go_exported_library() rule builds a Go code into C shared or static library
+    {/param}
+    {param content}
+
+{call buck.rule}
+{param status: 'UNFROZEN' /}
+{param overview}
+<p>
+  A go_exported_library() rule builds a C library from the supplied set of Go source files
+  and dependencies. This is done via <code>-buildmode</code> flag and "//export" annotations in the code.
+</p>
+<p>
+  {call go_common.supported_language_version /}
+</p>
+{/param}
+
+{param args}
+
+{call buck.arg}
+  {param name: 'name' /}
+  {param desc}
+  The name of the rule.
+  {/param}
+{/call}
+
+{call go_common.srcs_arg /}
+
+{call go_common.deps_arg /}
+
+{call buck.arg}
+  {param name : 'build_mode' /}
+  {param desc}
+  Determines the build mode (equivalent of <code>-buildmode</code>). Can be
+  one of the following values: <code>c_archive</code>, <code>c_shared</code>.
+  This argument is valid only if at there is at least one <code>cgo_library</deps> declared in deps.
+  In addition you should make sure that <code>-shared</code> flag is added to <code>compiler_flags</code>
+  and go version under <code>go.goroot</code> is compiled with that flag present in:
+  <code>gcflags</code>, <code>ldflags</code> and <code>asmflags</code>
+  {/param}
+{/call}
+
+{call go_common.link_style_arg /}
+
+{call go_common.link_mode_arg /}
+
+{call go_common.compiler_flags_arg /}
+
+{call go_common.assembler_flags_arg /}
+
+{call go_common.linker_flags_arg /}
+
+{call go_common.external_linker_flags_arg /}
+
+{call buck.arg}
+  {param name: 'resources' /}
+  {param default : '[]' /}
+  {param desc}
+  Static files to be symlinked into the working directory of the test. You can access these in your
+  by opening the files as relative paths, e.g. <code>ioutil.ReadFile("testdata/input")</code>.
+  {/param}
+{/call}
+
+{/param} // close args
+
+{param examples}
+
+{call go_common.more_examples /}
+
+{literal}<pre class="prettyprint lang-py">
+go_exported_library(
+    name = "shared",
+    srcs = ["main.go"],
+    build_mode = "c_shared",
+    compiler_flags = ["-shared"],
+    deps = [":example"],
+)
+
+cgo_library(
+    name = "example",
+    package_name = "cgo",
+    srcs = [
+        "export-to-c.go",  # file with //export annotations
+    ],
+    cgo_compiler_flags = [],
+    compiler_flags = [],
+    headers = [],
+)
+
+cxx_genrule(
+    name = "cgo_exported_headers",
+    out = "includes",
+    cmd = (
+        "mkdir -p $OUT && " +
+        "cat `dirname $(location :shared)`/includes/*.h > $OUT/_cgo_export.h"
+    ),
+)
+
+prebuilt_cxx_library(
+    name = "cxx_so_with_header",
+    header_dirs = [":cgo_exported_headers"],
+    shared_lib = ":shared",
+)
+</pre>{/literal}
+{/param}
+
+{/call} // close buck.rule
+
+    {/param}
+  {/call}
+{/template}

src/com/facebook/buck/features/go/GoBinary.java

@@ -59,6 +59,7 @@ public class GoBinary extends AbstractBuildRuleWithDeclaredAndExtraDeps
   @AddToRuleKey private final Linker cxxLinker;
   @AddToRuleKey private final ImmutableList<Arg> linkerArgs;
   @AddToRuleKey private final ImmutableList<Arg> cxxLinkerArgs;
+  @AddToRuleKey private final GoLinkStep.BuildMode buildMode;
   @AddToRuleKey private final GoLinkStep.LinkMode linkMode;
   @AddToRuleKey private final GoPlatform platform;
 
@@ -77,6 +78,7 @@ public GoBinary(
       GoCompile mainObject,
       Tool linker,
       Linker cxxLinker,
+      GoLinkStep.BuildMode buildMode,
       GoLinkStep.LinkMode linkMode,
       ImmutableList<Arg> linkerArgs,
       ImmutableList<Arg> cxxLinkerArgs,
@@ -93,15 +95,13 @@ public GoBinary(
     this.platform = platform;
     this.withDownwardApi = withDownwardApi;
 
-    String outputFormat = "%s/" + buildTarget.getShortName();
-    if (platform.getGoOs() == GoOs.WINDOWS) {
-      outputFormat = outputFormat + ".exe";
-    }
+    String outputFormat = getOutputFormat(buildTarget, platform, buildMode);
     this.output =
         BuildTargetPaths.getGenPath(projectFilesystem.getBuckPaths(), buildTarget, outputFormat);
 
     this.linkerArgs = linkerArgs;
     this.linkMode = linkMode;
+    this.buildMode = buildMode;
   }
 
   @Override
@@ -124,12 +124,37 @@ protected RelPath getPathToBinaryDirectory() {
     return output.getParent();
   }
 
+  private String getOutputFormat(
+      BuildTarget buildTarget, GoPlatform platform, GoLinkStep.BuildMode buildMode) {
+    String outputFormat = "%s/" + buildTarget.getShortName();
+
+    switch (buildMode) {
+      case C_SHARED:
+        if (platform.getGoOs() == GoOs.DARWIN) {
+          return outputFormat + ".dylib";
+        }
+        if (platform.getGoOs() == GoOs.WINDOWS) {
+          return outputFormat + ".dll";
+        }
+        return outputFormat + ".so";
+      case C_ARCHIVE:
+        return outputFormat + ".a";
+      case EXECUTABLE:
+        if (platform.getGoOs() == GoOs.WINDOWS) {
+          return outputFormat + ".exe";
+        }
+    }
+
+    return outputFormat;
+  }
+
   @Override
   public ImmutableList<Step> getBuildSteps(
       BuildContext context, BuildableContext buildableContext) {
 
     buildableContext.recordArtifact(output.getPath());
 
+    ProjectFilesystem filesystem = getProjectFilesystem();
     SourcePathResolverAdapter resolver = context.getSourcePathResolver();
     ImmutableList.Builder<Step> steps = ImmutableList.builder();
 
@@ -151,9 +176,7 @@ public ImmutableList<Step> getBuildSteps(
         steps.add(
             MkdirStep.of(
                 BuildCellRelativePath.fromCellRelativePath(
-                    context.getBuildCellRootPath(),
-                    getProjectFilesystem(),
-                    outputResourcePath.getParent())));
+                    context.getBuildCellRootPath(), filesystem, outputResourcePath.getParent())));
         steps.add(
             CopyStep.forDirectory(
                 resolver.getCellUnsafeRelPath(resource),
@@ -163,9 +186,7 @@ public ImmutableList<Step> getBuildSteps(
         steps.add(
             MkdirStep.of(
                 BuildCellRelativePath.fromCellRelativePath(
-                    context.getBuildCellRootPath(),
-                    getProjectFilesystem(),
-                    outputResourcePath.getParent())));
+                    context.getBuildCellRootPath(), filesystem, outputResourcePath.getParent())));
         steps.add(CopyStep.forFile(resolver.getCellUnsafeRelPath(resource), outputResourcePath));
       }
     }
@@ -212,7 +233,7 @@ public ImmutableList<Step> getBuildSteps(
             ImmutableList.of(linkTree.getRoot()),
             platform,
             resolver.getCellUnsafeRelPath(mainObject.getSourcePathToOutput()).getPath(),
-            GoLinkStep.BuildMode.EXECUTABLE,
+            buildMode,
             linkMode,
             output.getPath(),
             ProjectFilesystemUtils.relativize(

src/com/facebook/buck/features/go/GoBinaryDescription.java

@@ -116,6 +116,7 @@ public BuildRule createBuildRule(
         goBuckConfig,
         downwardApiConfig,
         args.getLinkStyle().orElse(Linker.LinkableDepType.STATIC_PIC),
+        GoLinkStep.BuildMode.EXECUTABLE,
         args.getLinkMode(),
         args.getSrcs(),
         args.getResources(),

src/com/facebook/buck/features/go/GoDescriptionsProvider.java

@@ -41,6 +41,7 @@ public Collection<Description<?>> getDescriptions(DescriptionCreationContext con
 
     return Arrays.asList(
         new GoBinaryDescription(goBuckConfig, downwardApiConfig, toolchainProvider),
+        new GoExportedLibraryDescription(goBuckConfig, downwardApiConfig, toolchainProvider),
         new GoLibraryDescription(goBuckConfig, downwardApiConfig, toolchainProvider),
         new CgoLibraryDescription(
             goBuckConfig, cxxBuckConfig, downwardApiConfig, toolchainProvider),

src/com/facebook/buck/features/go/GoDescriptors.java

@@ -321,6 +321,7 @@ static GoBinary createGoBinaryRule(
       GoBuckConfig goBuckConfig,
       DownwardApiConfig downwardApiConfig,
       Linker.LinkableDepType linkStyle,
+      GoLinkStep.BuildMode buildMode,
       Optional<GoLinkStep.LinkMode> linkMode,
       ImmutableSet<SourcePath> srcs,
       ImmutableSortedSet<SourcePath> resources,
@@ -429,7 +430,9 @@ static GoBinary createGoBinaryRule(
     if (!linkMode.isPresent()) {
       linkMode =
           Optional.of(
-              (cxxLinkerArgs.size() > 0)
+              (cxxLinkerArgs.size() > 0
+                      || buildMode == GoLinkStep.BuildMode.C_SHARED
+                      || buildMode == GoLinkStep.BuildMode.C_ARCHIVE)
                   ? GoLinkStep.LinkMode.EXTERNAL
                   : GoLinkStep.LinkMode.INTERNAL);
     }
@@ -455,6 +458,7 @@ static GoBinary createGoBinaryRule(
         library,
         platform.getLinker(),
         cxxLinker,
+        buildMode,
         linkMode.get(),
         ImmutableList.copyOf(linkerArgs),
         cxxLinkerArgs,
@@ -508,6 +512,7 @@ static Tool getTestMainGenerator(
                   goBuckConfig,
                   downwardApiConfig,
                   Linker.LinkableDepType.STATIC_PIC,
+                  GoLinkStep.BuildMode.EXECUTABLE,
                   Optional.empty(),
                   ImmutableSet.of(writeFile.getSourcePathToOutput()),
                   ImmutableSortedSet.of(),