Merge #2059

2059: fix(wasi) Fix the logic behind inherited/captured `stdin`, `stdout` and `stderr` r=Hywan a=Hywan

# Description

This patch is both a fix and a feature!

First, let's no longer derive from `Default` for `wasi_config_t`. By
default, we want to inherit `stdin`, `stdout` and `stderr`. The
default for `bool` is `false`; we want `true` here.

Second, let's update `wasi_config_new` to correctly set `inherit_*`
fields to `true`.

Third, lets' create `wasi_config_capture_*` functions. By default,
`std*` are inherited, so we need functions to capture them. That's the
new feature this patch introduces. The `wasi_config_inherit_*`
functions are kept for the sake of backward compatibility. Ideally, we
would want an API like `wasi_config_capture_*(capture: bool)`, but it
would duplicate the API somehow.

Fourth, let's fix `wasi_env_new`. We want to capture `stdout` and
`stderr` if and only if the `inherit_*` fields are set to
`false`. There was bug here. That's why everything was working
correctly by the way: `bool::default()` is `false`, and we have this
inverted condition here, so everything was working as expected because
of a double error. The only bug was that it wasn't possible to capture
`std*` before.

# Review

- [x] Add a short description of the the change to the CHANGELOG.md file


Co-authored-by: Ivan Enderlin <ivan@mnt.io>

CHANGELOG.md

@@ -8,6 +8,7 @@
 ## **[Unreleased]**
 
 ### Added
+- [#2059](https://github.com/wasmerio/wasmer/pull/2059) Ability to capture `stdout` and `stderr` with WASI in the C API.
 - [#2040](https://github.com/wasmerio/wasmer/pull/2040) Add `InstanceHandle::vmoffsets` to expose the offsets of the `vmctx` region.
 - [#2026](https://github.com/wasmerio/wasmer/pull/2010) Expose trap code of a `RuntimeError`, if it's a `Trap`.
 

lib/c-api/build.rs

@@ -401,13 +401,16 @@ fn exclude_items_from_deprecated(builder: Builder) -> Builder {
 fn exclude_items_from_wasm_c_api(builder: Builder) -> Builder {
     builder
         .exclude_item("wasi_config_arg")
+        .exclude_item("wasi_config_capture_stderr")
+        .exclude_item("wasi_config_capture_stdin")
+        .exclude_item("wasi_config_capture_stdout")
         .exclude_item("wasi_config_env")
-        .exclude_item("wasi_config_mapdir")
-        .exclude_item("wasi_config_preopen_dir")
         .exclude_item("wasi_config_inherit_stderr")
         .exclude_item("wasi_config_inherit_stdin")
         .exclude_item("wasi_config_inherit_stdout")
+        .exclude_item("wasi_config_mapdir")
         .exclude_item("wasi_config_new")
+        .exclude_item("wasi_config_preopen_dir")
         .exclude_item("wasi_config_t")
         .exclude_item("wasi_env_delete")
         .exclude_item("wasi_env_new")

lib/c-api/src/wasm_c_api/wasi/mod.rs

@@ -23,13 +23,12 @@ use wasmer_wasi::{
     WasiStateBuilder, WasiVersion,
 };
 
-#[derive(Debug, Default)]
+#[derive(Debug)]
 #[allow(non_camel_case_types)]
 pub struct wasi_config_t {
     inherit_stdout: bool,
     inherit_stderr: bool,
     inherit_stdin: bool,
-    /// cbindgen:ignore
     state_builder: WasiStateBuilder,
 }
 
@@ -43,8 +42,10 @@ pub unsafe extern "C" fn wasi_config_new(
     let prog_name = c_try!(name_c_str.to_str());
 
     Some(Box::new(wasi_config_t {
+        inherit_stdout: true,
+        inherit_stderr: true,
+        inherit_stdin: true,
         state_builder: WasiState::new(prog_name),
-        ..wasi_config_t::default()
     }))
 }
 
@@ -132,14 +133,31 @@ pub unsafe extern "C" fn wasi_config_mapdir(
     true
 }
 
+#[no_mangle]
+pub extern "C" fn wasi_config_capture_stdout(config: &mut wasi_config_t) {
+    config.inherit_stdout = false;
+}
+
 #[no_mangle]
 pub extern "C" fn wasi_config_inherit_stdout(config: &mut wasi_config_t) {
     config.inherit_stdout = true;
 }
+
+#[no_mangle]
+pub extern "C" fn wasi_config_capture_stderr(config: &mut wasi_config_t) {
+    config.inherit_stderr = false;
+}
+
 #[no_mangle]
 pub extern "C" fn wasi_config_inherit_stderr(config: &mut wasi_config_t) {
     config.inherit_stderr = true;
 }
+
+//#[no_mangle]
+//pub extern "C" fn wasi_config_capture_stdin(config: &mut wasi_config_t) {
+//    config.inherit_stdin = false;
+//}
+
 #[no_mangle]
 pub extern "C" fn wasi_config_inherit_stdin(config: &mut wasi_config_t) {
     config.inherit_stdin = true;
@@ -154,18 +172,22 @@ pub struct wasi_env_t {
 /// Takes ownership over the `wasi_config_t`.
 #[no_mangle]
 pub extern "C" fn wasi_env_new(mut config: Box<wasi_config_t>) -> Option<Box<wasi_env_t>> {
-    if config.inherit_stdout {
+    if !config.inherit_stdout {
         config
             .state_builder
             .stdout(Box::new(capture_files::OutputCapturer::new()));
     }
-    if config.inherit_stderr {
+
+    if !config.inherit_stderr {
         config
             .state_builder
             .stderr(Box::new(capture_files::OutputCapturer::new()));
     }
+
     // TODO: impl capturer for stdin
+
     let wasi_state = c_try!(config.state_builder.build());
+
     Some(Box::new(wasi_env_t {
         inner: WasiEnv::new(wasi_state),
     }))

lib/c-api/wasmer_wasm.h

@@ -128,6 +128,14 @@ typedef struct wasi_version_t wasi_version_t;
 void wasi_config_arg(wasi_config_t *config, const char *arg);
 #endif
 
+#if defined(WASMER_WASI_ENABLED)
+void wasi_config_capture_stderr(wasi_config_t *config);
+#endif
+
+#if defined(WASMER_WASI_ENABLED)
+void wasi_config_capture_stdout(wasi_config_t *config);
+#endif
+
 #if defined(WASMER_WASI_ENABLED)
 void wasi_config_env(wasi_config_t *config, const char *key, const char *value);
 #endif