From c564d2d5a46af4c213e424ee5a7ad7ff9cb2ba3a Mon Sep 17 00:00:00 2001
From: Ivan Lozano <ivanlozano@google.com>
Date: Tue, 4 Aug 2020 15:43:37 -0400
Subject: [PATCH] Add support for custom bindgen binaries.

In some cases customized logic is required to generate the expected
bindgen bindings. This adds support for rust_bindgen modules to define a
HostTool module to use instead of bindgen.

Bug: 161816141
Test: New Soong tests pass.
Test: Local test case shows custom_binary module being used for bindgen
      generation.

Change-Id: Id52aec4f25c38206d7e585d8e662be7836aa1d4b
---
 rust/bindgen.go      | 25 +++++++++++++++++++++----
 rust/bindgen_test.go | 26 ++++++++++++++++++++++++++
 rust/rust.go         | 16 ++++++++++++----
 3 files changed, 59 insertions(+), 8 deletions(-)

diff --git a/rust/bindgen.go b/rust/bindgen.go
index 403f4665a..2224a9cca 100644
--- a/rust/bindgen.go
+++ b/rust/bindgen.go
@@ -41,12 +41,12 @@ var (
 	bindgen = pctx.AndroidStaticRule("bindgen",
 		blueprint.RuleParams{
 			Command: "CLANG_PATH=$bindgenClang LIBCLANG_PATH=$bindgenLibClang RUSTFMT=${config.RustBin}/rustfmt " +
-				"$bindgenCmd $flags $in -o $out -- -MD -MF $out.d $cflags",
-			CommandDeps: []string{"$bindgenCmd"},
+				"$cmd $flags $in -o $out -- -MD -MF $out.d $cflags",
+			CommandDeps: []string{"$cmd"},
 			Deps:        blueprint.DepsGCC,
 			Depfile:     "$out.d",
 		},
-		"flags", "cflags")
+		"cmd", "flags", "cflags")
 )
 
 func init() {
@@ -76,6 +76,12 @@ type BindgenProperties struct {
 	// list of shared libraries that provide headers for this binding.
 	Shared_libs []string `android:"arch_variant"`
 
+	// module name of a custom binary/script which should be used instead of the 'bindgen' binary. This custom
+	// binary must expect arguments in a similar fashion to bindgen, e.g.
+	//
+	// "my_bindgen [flags] wrapper_header.h -o [output_path] -- [clang flags]"
+	Custom_bindgen string `android:"path"`
+
 	//TODO(b/161141999) Add support for headers from cc_library_header modules.
 }
 
@@ -130,17 +136,28 @@ func (b *bindgenDecorator) generateSource(ctx android.ModuleContext, deps PathDe
 
 	outputFile := android.PathForModuleOut(ctx, b.baseSourceProvider.getStem(ctx)+".rs")
 
+	var cmd, cmdDesc string
+	if b.Properties.Custom_bindgen != "" {
+		cmd = ctx.GetDirectDepWithTag(b.Properties.Custom_bindgen, customBindgenDepTag).(*Module).HostToolPath().String()
+		cmdDesc = b.Properties.Custom_bindgen
+	} else {
+		cmd = "$bindgenCmd"
+		cmdDesc = "bindgen"
+	}
+
 	ctx.Build(pctx, android.BuildParams{
 		Rule:        bindgen,
-		Description: "bindgen " + wrapperFile.Path().Rel(),
+		Description: strings.Join([]string{cmdDesc, wrapperFile.Path().Rel()}, " "),
 		Output:      outputFile,
 		Input:       wrapperFile.Path(),
 		Implicits:   implicits,
 		Args: map[string]string{
+			"cmd":    cmd,
 			"flags":  strings.Join(bindgenFlags, " "),
 			"cflags": strings.Join(cflags, " "),
 		},
 	})
+
 	b.baseSourceProvider.outputFile = outputFile
 	return outputFile
 }
diff --git a/rust/bindgen_test.go b/rust/bindgen_test.go
index c42834843..0b529ca5a 100644
--- a/rust/bindgen_test.go
+++ b/rust/bindgen_test.go
@@ -55,3 +55,29 @@ func TestRustBindgen(t *testing.T) {
 		t.Errorf("missing static_libs exported includes in rust_bindgen rule: cflags %#v", libbindgen.Args["cflags"])
 	}
 }
+
+func TestRustBindgenCustomBindgen(t *testing.T) {
+	ctx := testRust(t, `
+		rust_bindgen {
+			name: "libbindgen",
+			wrapper_src: "src/any.h",
+			crate_name: "bindgen",
+			stem: "libbindgen",
+			source_stem: "bindings",
+			custom_bindgen: "my_bindgen"
+		}
+		rust_binary_host {
+			name: "my_bindgen",
+			srcs: ["foo.rs"],
+		}
+	`)
+
+	libbindgen := ctx.ModuleForTests("libbindgen", "android_arm64_armv8-a").Output("bindings.rs")
+
+	// The rule description should contain the custom binary name rather than bindgen, so checking the description
+	// should be sufficient.
+	if !strings.Contains(libbindgen.Description, "my_bindgen") {
+		t.Errorf("Custom bindgen binary %s not used for libbindgen: rule description %#v", "my_bindgen",
+			libbindgen.Description)
+	}
+}
diff --git a/rust/rust.go b/rust/rust.go
index 01952477e..7ec2d736b 100644
--- a/rust/rust.go
+++ b/rust/rust.go
@@ -722,10 +722,11 @@ type dependencyTag struct {
 }
 
 var (
-	rlibDepTag       = dependencyTag{name: "rlibTag", library: true}
-	dylibDepTag      = dependencyTag{name: "dylib", library: true}
-	procMacroDepTag  = dependencyTag{name: "procMacro", proc_macro: true}
-	testPerSrcDepTag = dependencyTag{name: "rust_unit_tests"}
+	customBindgenDepTag = dependencyTag{name: "customBindgenTag"}
+	rlibDepTag          = dependencyTag{name: "rlibTag", library: true}
+	dylibDepTag         = dependencyTag{name: "dylib", library: true}
+	procMacroDepTag     = dependencyTag{name: "procMacro", proc_macro: true}
+	testPerSrcDepTag    = dependencyTag{name: "rust_unit_tests"}
 )
 
 type autoDep struct {
@@ -1009,6 +1010,13 @@ func (mod *Module) DepsMutator(actx android.BottomUpMutatorContext) {
 		actx.AddVariationDependencies(commonDepVariations, cc.CrtEndDepTag, deps.CrtEnd)
 	}
 
+	if mod.sourceProvider != nil {
+		if bindgen, ok := mod.sourceProvider.(*bindgenDecorator); ok &&
+			bindgen.Properties.Custom_bindgen != "" {
+			actx.AddFarVariationDependencies(ctx.Config().BuildOSTarget.Variations(), customBindgenDepTag,
+				bindgen.Properties.Custom_bindgen)
+		}
+	}
 	// proc_macros are compiler plugins, and so we need the host arch variant as a dependendcy.
 	actx.AddFarVariationDependencies(ctx.Config().BuildOSTarget.Variations(), procMacroDepTag, deps.ProcMacros...)
 }