Add dependency tags to apex available errors

Having dependency tags in the dependency path that shows why a specific
module is considered part of an apex makes it easier to understand why
that is the case and detect possible issues.

Bug: 152762638
Bug: 153306490
Test: m nothing
Merged-In: Iba2a8a5a6abe03dadee456e760aa4373cd00c07b
Change-Id: Iba2a8a5a6abe03dadee456e760aa4373cd00c07b

android/module.go

@@ -128,6 +128,13 @@ type BaseModuleContext interface {
 	// and returns a top-down dependency path from a start module to current child module.
 	GetWalkPath() []Module
 
+	// GetTagPath is supposed to be called in visit function passed in WalkDeps()
+	// and returns a top-down dependency tags path from a start module to current child module.
+	// It has one less entry than GetWalkPath() as it contains the dependency tags that
+	// exist between each adjacent pair of modules in the GetWalkPath().
+	// GetTagPath()[i] is the tag between GetWalkPath()[i] and GetWalkPath()[i+1]
+	GetTagPath() []blueprint.DependencyTag
+
 	AddMissingDependencies(missingDeps []string)
 
 	Target() Target
@@ -1386,6 +1393,7 @@ type baseModuleContext struct {
 	debug         bool
 
 	walkPath []Module
+	tagPath  []blueprint.DependencyTag
 
 	strictVisitDeps bool // If true, enforce that all dependencies are enabled
 }
@@ -1675,6 +1683,7 @@ func (b *baseModuleContext) WalkDepsBlueprint(visit func(blueprint.Module, bluep
 
 func (b *baseModuleContext) WalkDeps(visit func(Module, Module) bool) {
 	b.walkPath = []Module{b.Module()}
+	b.tagPath = []blueprint.DependencyTag{}
 	b.bp.WalkDeps(func(child, parent blueprint.Module) bool {
 		childAndroidModule, _ := child.(Module)
 		parentAndroidModule, _ := parent.(Module)
@@ -1682,8 +1691,10 @@ func (b *baseModuleContext) WalkDeps(visit func(Module, Module) bool) {
 			// record walkPath before visit
 			for b.walkPath[len(b.walkPath)-1] != parentAndroidModule {
 				b.walkPath = b.walkPath[0 : len(b.walkPath)-1]
+				b.tagPath = b.tagPath[0 : len(b.tagPath)-1]
 			}
 			b.walkPath = append(b.walkPath, childAndroidModule)
+			b.tagPath = append(b.tagPath, b.OtherModuleDependencyTag(childAndroidModule))
 			return visit(childAndroidModule, parentAndroidModule)
 		} else {
 			return false
@@ -1695,6 +1706,10 @@ func (b *baseModuleContext) GetWalkPath() []Module {
 	return b.walkPath
 }
 
+func (b *baseModuleContext) GetTagPath() []blueprint.DependencyTag {
+	return b.tagPath
+}
+
 func (m *moduleContext) VisitAllModuleVariants(visit func(Module)) {
 	m.bp.VisitAllModuleVariants(func(module blueprint.Module) {
 		visit(module.(Module))

apex/apex.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"path"
 	"path/filepath"
+	"regexp"
 	"sort"
 	"strings"
 	"sync"
@@ -1807,6 +1808,24 @@ func (a *apexBundle) minSdkVersion(ctx android.BaseModuleContext) int {
 	return intVer
 }
 
+// A regexp for removing boilerplate from BaseDependencyTag from the string representation of
+// a dependency tag.
+var tagCleaner = regexp.MustCompile(`\QBaseDependencyTag:blueprint.BaseDependencyTag{}\E(, )?`)
+
+func PrettyPrintTag(tag blueprint.DependencyTag) string {
+	// Use tag's custom String() method if available.
+	if stringer, ok := tag.(fmt.Stringer); ok {
+		return stringer.String()
+	}
+
+	// Otherwise, get a default string representation of the tag's struct.
+	tagString := fmt.Sprintf("%#v", tag)
+
+	// Remove the boilerplate from BaseDependencyTag as it adds no value.
+	tagString = tagCleaner.ReplaceAllString(tagString, "")
+	return tagString
+}
+
 // Ensures that the dependencies are marked as available for this APEX
 func (a *apexBundle) checkApexAvailability(ctx android.ModuleContext) {
 	// Let's be practical. Availability for test, host, and the VNDK apex isn't important
@@ -1834,8 +1853,11 @@ func (a *apexBundle) checkApexAvailability(ctx android.ModuleContext) {
 			return true
 		}
 		message := ""
-		for _, m := range ctx.GetWalkPath()[1:] {
-			message = fmt.Sprintf("%s\n    -> %s", message, m.String())
+		tagPath := ctx.GetTagPath()
+		// Skip the first module as that will be added at the start of the error message by ctx.ModuleErrorf().
+		walkPath := ctx.GetWalkPath()[1:]
+		for i, m := range walkPath {
+			message = fmt.Sprintf("%s\n           via tag %s\n    -> %s", message, PrettyPrintTag(tagPath[i]), m.String())
 		}
 		ctx.ModuleErrorf("%q requires %q that is not available for the APEX. Dependency path:%s", fromName, toName, message)
 		// Visit this module's dependencies to check and report any issues with their availability.

apex/apex_test.go

@@ -3516,11 +3516,17 @@ func TestApexAvailable_DirectDep(t *testing.T) {
 func TestApexAvailable_IndirectDep(t *testing.T) {
 	// libbbaz is an indirect dep
 	testApexError(t, `requires "libbaz" that is not available for the APEX. Dependency path:
+.*via tag apex\.dependencyTag.*"sharedLib".*
 .*-> libfoo.*link:shared.*
+.*via tag cc\.DependencyTag.*"reuse objects".*
 .*-> libfoo.*link:static.*
+.*via tag cc\.DependencyTag.*"shared from static".*
 .*-> libbar.*link:shared.*
+.*via tag cc\.DependencyTag.*"reuse objects".*
 .*-> libbar.*link:static.*
+.*via tag cc\.DependencyTag.*"shared from static".*
 .*-> libbaz.*link:shared.*
+.*via tag cc\.DependencyTag.*"reuse objects".*
 .*-> libbaz.*link:static.*`, `
 	apex {
 		name: "myapex",