Rust: Vendor support for Rust static libraries.

We don't have Rust VNDK support yet, but static linkage can be
supported in the interim. This adds support for making rust_ffi_static
libraries available to CC vendor modules.

Since rust_ffi_static modules will link against rlibs, we allow rlib
linkage into vendor as well, but only for the variants which use the
rlib libstd.

Bug: 172525289
Test: New Soong tests pass
Test: Example vendor cc_binary links against rust_ffi_static module.
Change-Id: Idf3aeb51e32293866f1ad965e329aa6b9e0bf2ef
diff --git a/rust/image.go b/rust/image.go
new file mode 100644
index 0000000..4951d2b
--- /dev/null
+++ b/rust/image.go
@@ -0,0 +1,153 @@
+// Copyright 2020 The Android Open Source Project
+//
+// 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.
+
+package rust
+
+import (
+	"strings"
+
+	"android/soong/android"
+	"android/soong/cc"
+)
+
+var _ android.ImageInterface = (*Module)(nil)
+
+func (mod *Module) VendorRamdiskVariantNeeded(ctx android.BaseModuleContext) bool {
+	return false
+}
+
+func (mod *Module) CoreVariantNeeded(ctx android.BaseModuleContext) bool {
+	return mod.Properties.CoreVariantNeeded
+}
+
+func (mod *Module) RamdiskVariantNeeded(android.BaseModuleContext) bool {
+	return mod.InRamdisk()
+}
+
+func (mod *Module) RecoveryVariantNeeded(android.BaseModuleContext) bool {
+	return mod.InRecovery()
+}
+
+func (mod *Module) ExtraImageVariations(android.BaseModuleContext) []string {
+	return mod.Properties.ExtraVariants
+}
+
+func (ctx *moduleContext) ProductSpecific() bool {
+	return false
+}
+
+func (mod *Module) InRecovery() bool {
+	// TODO(b/165791368)
+	return false
+}
+
+func (mod *Module) OnlyInRamdisk() bool {
+	// TODO(b/165791368)
+	return false
+}
+
+func (mod *Module) OnlyInRecovery() bool {
+	// TODO(b/165791368)
+	return false
+}
+
+func (mod *Module) OnlyInVendorRamdisk() bool {
+	return false
+}
+
+// Returns true when this module is configured to have core and vendor variants.
+func (mod *Module) HasVendorVariant() bool {
+	return mod.IsVndk() || Bool(mod.VendorProperties.Vendor_available)
+}
+
+func (c *Module) VendorAvailable() bool {
+	return Bool(c.VendorProperties.Vendor_available)
+}
+
+func (c *Module) InProduct() bool {
+	return false
+}
+
+func (mod *Module) SetImageVariation(ctx android.BaseModuleContext, variant string, module android.Module) {
+	m := module.(*Module)
+	if strings.HasPrefix(variant, cc.VendorVariationPrefix) {
+		m.Properties.ImageVariationPrefix = cc.VendorVariationPrefix
+		m.Properties.VndkVersion = strings.TrimPrefix(variant, cc.VendorVariationPrefix)
+
+		// Makefile shouldn't know vendor modules other than BOARD_VNDK_VERSION.
+		// Hide other vendor variants to avoid collision.
+		vndkVersion := ctx.DeviceConfig().VndkVersion()
+		if vndkVersion != "current" && vndkVersion != "" && vndkVersion != m.Properties.VndkVersion {
+			m.Properties.HideFromMake = true
+			m.SkipInstall()
+		}
+	}
+}
+
+func (mod *Module) ImageMutatorBegin(mctx android.BaseModuleContext) {
+	vendorSpecific := mctx.SocSpecific() || mctx.DeviceSpecific()
+	platformVndkVersion := mctx.DeviceConfig().PlatformVndkVersion()
+
+	// Rust does not support installing to the product image yet.
+	if mod.VendorProperties.Product_available != nil {
+		mctx.PropertyErrorf("product_available",
+			"Rust modules do not yet support being available to the product image")
+	} else if mctx.ProductSpecific() {
+		mctx.PropertyErrorf("product_specific",
+			"Rust modules do not yet support installing to the product image.")
+	} else if mod.VendorProperties.Double_loadable != nil {
+		mctx.PropertyErrorf("double_loadable",
+			"Rust modules do not yet support double loading")
+	}
+
+	coreVariantNeeded := true
+	var vendorVariants []string
+
+	if mod.VendorProperties.Vendor_available != nil {
+		if vendorSpecific {
+			mctx.PropertyErrorf("vendor_available",
+				"doesn't make sense at the same time as `vendor: true`, `proprietary: true`, or `device_specific:true`")
+		}
+
+		if lib, ok := mod.compiler.(libraryInterface); ok {
+			// Explicitly disallow rust_ffi variants which produce shared libraries from setting vendor_available.
+			// Vendor variants do not produce an error for dylibs, rlibs with dylib-std linkage are disabled in the respective library
+			// mutators until support is added.
+			//
+			// We can't check shared() here because image mutator is called before the library mutator, so we need to
+			// check buildShared()
+			if lib.buildShared() {
+				mctx.PropertyErrorf("vendor_available",
+					"vendor_available can only be set for rust_ffi_static modules.")
+			} else if Bool(mod.VendorProperties.Vendor_available) == true {
+				vendorVariants = append(vendorVariants, platformVndkVersion)
+			}
+		}
+	}
+
+	if vendorSpecific {
+		if lib, ok := mod.compiler.(libraryInterface); !ok || (ok && !lib.static()) {
+			mctx.ModuleErrorf("Rust vendor specific modules are currently only supported for rust_ffi_static modules.")
+		} else {
+			coreVariantNeeded = false
+			vendorVariants = append(vendorVariants, platformVndkVersion)
+		}
+	}
+
+	mod.Properties.CoreVariantNeeded = coreVariantNeeded
+	for _, variant := range android.FirstUniqueStrings(vendorVariants) {
+		mod.Properties.ExtraVariants = append(mod.Properties.ExtraVariants, cc.VendorVariationPrefix+variant)
+	}
+
+}