patches/0003-Enable-embedding-android_logger-in-liblog_rust.patch

From ff9b04d9a87d2bda1281cf31e9df32c60133ef42 Mon Sep 17 00:00:00 2001
From: Marcin Radomski <dextero@google.com>
Date: Thu, 17 Aug 2023 16:07:56 +0000
Subject: [PATCH] Enable embedding android_logger in liblog_rust

Add default_log_impl cfg that, when enabled:
* Removes the dependency on env_logger,
* Imports all log crate symbols from current crate.

This makes it possible to embed android_logger as mod inside liblog_rust
crate, so that AndroidLogger can be used as default logger instead of a
NopLogger.

Changing that default prevents dropping logs when the logger is
uninitialized. This can happen by accident when an application doesn't
intialize the logger in all linker namespaces it pulls libraries from.
See discussion at b/294216366#comment7.

Bug: 275290559
Test: compile test app from aosp/2717614
Test: run it on a Cuttlefish device
Test: observe logcat logs on all level from FFI call
Test: observe all logs on non-FFI call without initializing the logger
Test: observe set log filter applying only to non-FFI call
Change-Id: I324f77d840101391299e2693acc6f814d062c659
---
 src/lib.rs | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index c22f07e..c2a3c08 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -67,20 +67,35 @@
 extern crate android_log_sys as log_ffi;
 extern crate once_cell;
 use once_cell::sync::OnceCell;
+#[cfg(default_log_impl)]
+use crate as log;
+#[cfg(not(default_log_impl))]
 #[macro_use]
 extern crate log;
 
+#[cfg(not(default_log_impl))]
 extern crate env_logger;
 
-use log::{Level, LevelFilter, Log, Metadata, Record};
+use self::log::{Level, LevelFilter, Log, Metadata, Record};
 #[cfg(target_os = "android")]
-use log_ffi::LogPriority;
+use self::log_ffi::LogPriority;
 use std::ffi::{CStr, CString};
 use std::fmt;
 use std::mem::{self, MaybeUninit};
 use std::ptr;
 
+#[cfg(default_log_impl)]
+pub mod env_logger {
+    pub mod filter {
+        pub struct Filter;
+        impl Filter {
+            pub fn matches(&self, _: &crate::Record) -> bool { true }
+        }
+    }
+}
+#[cfg(not(default_log_impl))]
 pub use env_logger::filter::{Builder as FilterBuilder, Filter};
+#[cfg(not(default_log_impl))]
 pub use env_logger::fmt::Formatter;
 
 pub(crate) type FormatFn = Box<dyn Fn(&mut dyn fmt::Write, &Record) -> fmt::Result + Sync + Send>;
@@ -499,6 +514,12 @@ pub fn init_once(config: Config) {
     } else if let Some(level) = log_level {
         log::set_max_level(level);
     }
+    // On Android, log crate is patched to default to LevelFilter::Trace rather than Off. Preserve
+    // the existing "android_logger default level is Off" behavior by explicitly setting the level.
+    #[cfg(target_os = "android")]
+    if log_level.is_none() {
+        log::set_max_level(LevelFilter::Off);
+    }
 }
 
 // FIXME: When `maybe_uninit_uninit_array ` is stabilized, use it instead of this helper
@@ -553,6 +574,7 @@ mod tests {
 
     // Test whether the filter gets called correctly. Not meant to be exhaustive for all filter
     // options, as these are handled directly by the filter itself.
+    #[cfg(not(default_log_impl))]
     #[test]
     fn config_filter_match() {
         let info_record = Record::builder().level(Level::Info).build();
-- 
2.42.0.rc1.204.g551eb34607-goog