idmap2: switch to improved Result class

Remove the old std::optional based Result class, replace uses with the
new std::variant based Result class.

Test: make idmap2_tests
Change-Id: I401cb36e5af06133a2872d835cf29bfb0b106597
diff --git a/cmds/idmap2/libidmap2/Idmap.cpp b/cmds/idmap2/libidmap2/Idmap.cpp
index ec498ff..a1341fb 100644
--- a/cmds/idmap2/libidmap2/Idmap.cpp
+++ b/cmds/idmap2/libidmap2/Idmap.cpp
@@ -121,7 +121,9 @@
 Result<uint32_t> GetCrc(const ZipFile& zip) {
   const Result<uint32_t> a = zip.Crc("resources.arsc");
   const Result<uint32_t> b = zip.Crc("AndroidManifest.xml");
-  return a && b ? Result<uint32_t>(*a ^ *b) : kResultError;
+  return a && b
+             ? Result<uint32_t>(*a ^ *b)
+             : Error("Couldn't get CRC for \"%s\"", a ? "AndroidManifest.xml" : "resources.arsc");
 }
 
 }  // namespace
@@ -355,9 +357,9 @@
     return nullptr;
   }
 
-  Result<utils::OverlayManifestInfo> overlay_info =
-      utils::ExtractOverlayManifestInfo(overlay_apk_path, out_error);
+  auto overlay_info = utils::ExtractOverlayManifestInfo(overlay_apk_path);
   if (!overlay_info) {
+    out_error << "error: " << overlay_info.GetErrorMessage() << std::endl;
     return nullptr;
   }
 
diff --git a/cmds/idmap2/libidmap2/Policies.cpp b/cmds/idmap2/libidmap2/Policies.cpp
index 6649288..c6ba87d 100644
--- a/cmds/idmap2/libidmap2/Policies.cpp
+++ b/cmds/idmap2/libidmap2/Policies.cpp
@@ -16,7 +16,6 @@
 
 #include <iterator>
 #include <map>
-#include <sstream>
 #include <string>
 #include <vector>
 
@@ -39,16 +38,14 @@
 };
 }  // namespace
 
-Result<PolicyBitmask> PoliciesToBitmask(const std::vector<std::string>& policies,
-                                        std::ostream& err) {
+Result<PolicyBitmask> PoliciesToBitmask(const std::vector<std::string>& policies) {
   PolicyBitmask bitmask = 0;
   for (const std::string& policy : policies) {
     const auto iter = kStringToFlag.find(policy);
     if (iter != kStringToFlag.end()) {
       bitmask |= iter->second;
     } else {
-      err << "error: unknown policy \"" << policy << "\"";
-      return kResultError;
+      return Error("unknown policy \"%s\"", policy.c_str());
     }
   }
 
diff --git a/cmds/idmap2/libidmap2/RawPrintVisitor.cpp b/cmds/idmap2/libidmap2/RawPrintVisitor.cpp
index b78e942..1149c90 100644
--- a/cmds/idmap2/libidmap2/RawPrintVisitor.cpp
+++ b/cmds/idmap2/libidmap2/RawPrintVisitor.cpp
@@ -75,7 +75,7 @@
                                             type_entry.GetEntryOffset() + i);
       const ResourceId overlay_resid =
           RESID(last_seen_package_id_, type_entry.GetOverlayTypeId(), entry);
-      Result<std::string> name;
+      Result<std::string> name(Error(""));
       if (target_package_loaded) {
         name = utils::ResToTypeEntryName(target_am_, target_resid);
       }
diff --git a/cmds/idmap2/libidmap2/ResourceUtils.cpp b/cmds/idmap2/libidmap2/ResourceUtils.cpp
index 7a984f3..a24836d 100644
--- a/cmds/idmap2/libidmap2/ResourceUtils.cpp
+++ b/cmds/idmap2/libidmap2/ResourceUtils.cpp
@@ -33,10 +33,10 @@
 
 namespace android::idmap2::utils {
 
-Result<std::string> WARN_UNUSED ResToTypeEntryName(const AssetManager2& am, ResourceId resid) {
+Result<std::string> ResToTypeEntryName(const AssetManager2& am, ResourceId resid) {
   AssetManager2::ResourceName name;
   if (!am.GetResourceName(resid, &name)) {
-    return {};
+    return Error("no resource 0x%08x in asset manager", resid);
   }
   std::string out;
   if (name.type != nullptr) {
@@ -50,36 +50,31 @@
   } else {
     out += Utf16ToUtf8(StringPiece16(name.entry16, name.entry_len));
   }
-  return {out};
+  return out;
 }
 
 Result<OverlayManifestInfo> ExtractOverlayManifestInfo(const std::string& path,
-                                                       std::ostream& out_error,
                                                        bool assert_overlay) {
   std::unique_ptr<const ZipFile> zip = ZipFile::Open(path);
   if (!zip) {
-    out_error << "error: failed to open " << path << " as a zip file" << std::endl;
-    return kResultError;
+    return Error("failed to open %s as a zip file", path.c_str());
   }
 
   std::unique_ptr<const MemoryChunk> entry = zip->Uncompress("AndroidManifest.xml");
   if (!entry) {
-    out_error << "error: failed to uncompress AndroidManifest.xml from " << path << std::endl;
-    return kResultError;
+    return Error("failed to uncompress AndroidManifest.xml from %s", path.c_str());
   }
 
   std::unique_ptr<const Xml> xml = Xml::Create(entry->buf, entry->size);
   if (!xml) {
-    out_error << "error: failed to parse AndroidManifest.xml from " << path << std::endl;
-    return kResultError;
+    return Error("failed to parse AndroidManifest.xml from %s", path.c_str());
   }
 
   OverlayManifestInfo info{};
   const auto tag = xml->FindTag("overlay");
   if (!tag) {
     if (assert_overlay) {
-      out_error << "error: <overlay> missing from AndroidManifest.xml of " << path << std::endl;
-      return kResultError;
+      return Error("<overlay> missing from AndroidManifest.xml of %s", path.c_str());
     }
     return info;
   }
@@ -87,8 +82,7 @@
   auto iter = tag->find("targetPackage");
   if (iter == tag->end()) {
     if (assert_overlay) {
-      out_error << "error: android:targetPackage missing from <overlay> of " << path << std::endl;
-      return kResultError;
+      return Error("android:targetPackage missing from <overlay> of %s", path.c_str());
     }
   } else {
     info.target_package = iter->second;
diff --git a/cmds/idmap2/libidmap2/Result.cpp b/cmds/idmap2/libidmap2/Result.cpp
index bd4fabd..471dab2 100644
--- a/cmds/idmap2/libidmap2/Result.cpp
+++ b/cmds/idmap2/libidmap2/Result.cpp
@@ -23,7 +23,7 @@
 namespace android::idmap2 {
 
 // NOLINTNEXTLINE(cert-dcl50-cpp)
-v2::Error::Error(const char* fmt, ...) {
+Error::Error(const char* fmt, ...) {
   va_list ap;
   va_start(ap, fmt);
   base::StringAppendV(&msg_, fmt, ap);
@@ -31,7 +31,7 @@
 }
 
 // NOLINTNEXTLINE(cert-dcl50-cpp)
-v2::Error::Error(const Error& parent, const char* fmt, ...) : msg_(parent.msg_) {
+Error::Error(const Error& parent, const char* fmt, ...) : msg_(parent.msg_) {
   msg_.append(" -> ");
 
   va_list ap;
diff --git a/cmds/idmap2/libidmap2/ZipFile.cpp b/cmds/idmap2/libidmap2/ZipFile.cpp
index 15ec3f9..0f07324 100644
--- a/cmds/idmap2/libidmap2/ZipFile.cpp
+++ b/cmds/idmap2/libidmap2/ZipFile.cpp
@@ -59,7 +59,10 @@
 Result<uint32_t> ZipFile::Crc(const std::string& entryPath) const {
   ::ZipEntry entry;
   int32_t status = ::FindEntry(handle_, ::ZipString(entryPath.c_str()), &entry);
-  return status == 0 ? Result<uint32_t>(entry.crc32) : kResultError;
+  if (status != 0) {
+    return Error("failed to find zip entry %s", entryPath.c_str());
+  }
+  return entry.crc32;
 }
 
 }  // namespace android::idmap2