Use one mutator for all bp2build conversion.

Each conversion required defining a separate mutator, which will each
operate on _all_ modules and requires each to repeat checks whether the
mutator should operator. Instead, we introduce a single mutator and
modules can define a ConvertWithBp2build to implement bp2build
conversion for that module.

Test: bp2build.sh
Bug: 183079158
Change-Id: I99d4b51f441c2903879092c5b56313d606d4338d
diff --git a/python/binary.go b/python/binary.go
index af02de6..99c6259 100644
--- a/python/binary.go
+++ b/python/binary.go
@@ -27,7 +27,6 @@
 
 func init() {
 	registerPythonBinaryComponents(android.InitRegistrationContext)
-	android.RegisterBp2BuildMutator("python_binary_host", PythonBinaryBp2Build)
 }
 
 func registerPythonBinaryComponents(ctx android.RegistrationContext) {
@@ -41,17 +40,7 @@
 	Python_version *string
 }
 
-func PythonBinaryBp2Build(ctx android.TopDownMutatorContext) {
-	m, ok := ctx.Module().(*Module)
-	if !ok || !m.ConvertWithBp2build(ctx) {
-		return
-	}
-
-	// a Module can be something other than a python_binary_host
-	if ctx.ModuleType() != "python_binary_host" {
-		return
-	}
-
+func pythonBinaryBp2Build(ctx android.TopDownMutatorContext, m *Module) {
 	var main *string
 	for _, propIntf := range m.GetProperties() {
 		if props, ok := propIntf.(*BinaryProperties); ok {
diff --git a/python/library.go b/python/library.go
index 9c92ebd..d026c13 100644
--- a/python/library.go
+++ b/python/library.go
@@ -17,8 +17,6 @@
 // This file contains the module types for building Python library.
 
 import (
-	"fmt"
-
 	"android/soong/android"
 	"android/soong/bazel"
 
@@ -27,8 +25,6 @@
 
 func init() {
 	registerPythonLibraryComponents(android.InitRegistrationContext)
-	android.RegisterBp2BuildMutator("python_library_host", PythonLibraryHostBp2Build)
-	android.RegisterBp2BuildMutator("python_library", PythonLibraryBp2Build)
 }
 
 func registerPythonLibraryComponents(ctx android.RegistrationContext) {
@@ -50,25 +46,7 @@
 	Srcs_version *string
 }
 
-func PythonLibraryHostBp2Build(ctx android.TopDownMutatorContext) {
-	pythonLibBp2Build(ctx, "python_library_host")
-}
-
-func PythonLibraryBp2Build(ctx android.TopDownMutatorContext) {
-	pythonLibBp2Build(ctx, "python_library")
-}
-
-func pythonLibBp2Build(ctx android.TopDownMutatorContext, modType string) {
-	m, ok := ctx.Module().(*Module)
-	if !ok || !m.ConvertWithBp2build(ctx) {
-		return
-	}
-
-	// a Module can be something other than a `modType`
-	if ctx.ModuleType() != modType {
-		return
-	}
-
+func pythonLibBp2Build(ctx android.TopDownMutatorContext, m *Module) {
 	// TODO(b/182306917): this doesn't fully handle all nested props versioned
 	// by the python version, which would have been handled by the version split
 	// mutator. This is sufficient for very simple python_library modules under
@@ -81,9 +59,7 @@
 	} else if !py2Enabled && py3Enabled {
 		python_version = &pyVersion3
 	} else if !py2Enabled && !py3Enabled {
-		panic(fmt.Errorf(
-			"error for '%s' module: bp2build's %s converter doesn't understand having "+
-				"neither py2 nor py3 enabled", m.Name(), modType))
+		ctx.ModuleErrorf("bp2build converter doesn't understand having neither py2 nor py3 enabled")
 	} else {
 		// do nothing, since python_version defaults to PY2ANDPY3
 	}
diff --git a/python/python.go b/python/python.go
index 401d91f..734ac57 100644
--- a/python/python.go
+++ b/python/python.go
@@ -23,6 +23,7 @@
 	"strings"
 
 	"android/soong/bazel"
+
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 
@@ -667,18 +668,25 @@
 }
 
 // isPythonLibModule returns whether the given module is a Python library Module or not
-// This is distinguished by the fact that Python libraries are not installable, while other Python
-// modules are.
 func isPythonLibModule(module blueprint.Module) bool {
 	if m, ok := module.(*Module); ok {
-		// Python library has no bootstrapper or installer
-		if m.bootstrapper == nil && m.installer == nil {
-			return true
-		}
+		return m.isLibrary()
 	}
 	return false
 }
 
+// This is distinguished by the fact that Python libraries are not installable, while other Python
+// modules are.
+func (p *Module) isLibrary() bool {
+	// Python library has no bootstrapper or installer
+	return p.bootstrapper == nil && p.installer == nil
+}
+
+func (p *Module) isBinary() bool {
+	_, ok := p.bootstrapper.(*binaryDecorator)
+	return ok
+}
+
 // collectPathsFromTransitiveDeps checks for source/data files for duplicate paths
 // for module and its transitive dependencies and collects list of data/source file
 // zips for transitive dependencies.
@@ -752,6 +760,14 @@
 	return true
 }
 
+func (p *Module) ConvertWithBp2build(ctx android.TopDownMutatorContext) {
+	if p.isLibrary() {
+		pythonLibBp2Build(ctx, p)
+	} else if p.isBinary() {
+		pythonBinaryBp2Build(ctx, p)
+	}
+}
+
 var Bool = proptools.Bool
 var BoolDefault = proptools.BoolDefault
 var String = proptools.String