Embed default resources in Servo applications using a servo-default-resources crate (#43182)

This PR considers the following constraints:

- Resources must be available when building servo via a published
crates.io package (i.e. no `../../../resources/<file>` file references).
- Minimal setup when writing tests (`nextest` spawns each test in its
own process, so we don't want to explicitly initialize the resource
handler for every `#[test]` fn)
- Use local resources when developing locally
- Support loading the resources from a proper resource directory if the
embedder wishes so, including via a custom mechanism, not necessarily as
files

(File) Resources that are only accessed from servoshell are out of scope
of this PR, since it mainly focusses on unblocking publishing `libservo`
to crates.io.

Baking the resources into the binary by default simplifies the setup a
lot. We already supported that before, but only for testing purposes and
explicitly not for production builds.

Using [`inventory`](https://crates.io/crates/inventory) adds a simple
way for the embedder to replace the default baked in resources, while
also keeping the test usage of baked in resources simple.

rippy.png is also referenced from image_cache - We simply duplicate it,
since the image is small, to avoid adding unnecessarily complex
solutions like adding a dedicated crate.


Testing: Covered by existing tests. [mach try
full](https://github.com/jschwe/servo/actions/runs/23811669469)
Fixes: Part of #43145

---------

Signed-off-by: Jonathan Schwender <schwenderjonathan@gmail.com>

ports/servoshell/Cargo.toml

@@ -41,7 +41,8 @@ OriginalFilename = "servoshell.exe"
 ProductName = "ServoShell"
 
 [features]
-default = ["gamepad", "servo/clipboard", "js_jit", "max_log_level", "webgpu", "webxr"]
+default = ["baked-in-resources", "gamepad", "servo/clipboard", "js_jit", "max_log_level", "webgpu", "webxr"]
+baked-in-resources = ["servo/baked-in-resources"]
 crown = ["servo/crown"]
 debugmozjs = ["servo/debugmozjs"]
 gamepad = ["servo/gamepad"]

ports/servoshell/desktop/cli.rs

@@ -12,7 +12,6 @@ use crate::prefs::{ArgumentParsingResult, parse_command_line_arguments};
 pub fn main() {
     crate::crash_handler::install();
     crate::init_crypto();
-    crate::resources::init();
 
     // TODO: once log-panics is released, can this be replaced by
     // log_panics::init()?

ports/servoshell/desktop/protocols/resource.rs

@@ -43,9 +43,7 @@ impl ResourceProtocolHandler {
             )));
         };
 
-        let file_path = crate::resources::resources_dir_path()
-            .join("resource_protocol")
-            .join(path);
+        let file_path = crate::resources::resource_protocol_dir_path().join(path);
 
         if !file_path.exists() || file_path.is_dir() {
             return Box::pin(std::future::ready(Response::network_error(

ports/servoshell/egl/android/mod.rs

@@ -4,8 +4,6 @@
 
 #![allow(non_snake_case)]
 
-mod resources;
-
 use std::cell::RefCell;
 use std::os::raw::{c_char, c_int, c_void};
 use std::ptr::NonNull;
@@ -23,7 +21,6 @@ use raw_window_handle::{
     AndroidDisplayHandle, AndroidNdkWindowHandle, DisplayHandle, RawDisplayHandle, RawWindowHandle,
     WindowHandle,
 };
-use resources::ResourceReaderInstance;
 pub use servo::MediaSessionPlaybackState;
 use servo::{
     self, DevicePixel, EventLoopWaker, InputMethodControl, LoadStatus, MediaSessionActionType,
@@ -165,7 +162,6 @@ pub extern "C" fn Java_org_servo_servoview_JNIServo_init<'local>(
     let host = Rc::new(HostCallbacks::new(callbacks_ref, &env));
 
     crate::init_crypto();
-    servo::resources::set(Box::new(ResourceReaderInstance::new()));
 
     let (opts, mut preferences, servoshell_preferences) =
         match parse_command_line_arguments(init_opts.args.as_slice()) {

ports/servoshell/egl/android/resources.rs

@@ -1,47 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
-use std::path::PathBuf;
-
-use servo::resources::{Resource, ResourceReaderMethods};
-
-pub(crate) struct ResourceReaderInstance;
-
-impl ResourceReaderInstance {
-    pub(crate) fn new() -> ResourceReaderInstance {
-        ResourceReaderInstance
-    }
-}
-
-impl ResourceReaderMethods for ResourceReaderInstance {
-    fn read(&self, res: Resource) -> Vec<u8> {
-        Vec::from(match res {
-            Resource::HstsPreloadList => {
-                &include_bytes!("../../../../resources/hsts_preload.fstmap")[..]
-            },
-            Resource::BadCertHTML => &include_bytes!("../../../../resources/badcert.html")[..],
-            Resource::NetErrorHTML => &include_bytes!("../../../../resources/neterror.html")[..],
-            Resource::BrokenImageIcon => &include_bytes!("../../../../resources/rippy.png")[..],
-            Resource::DomainList => &include_bytes!("../../../../resources/public_domains.txt")[..],
-            Resource::BluetoothBlocklist => {
-                &include_bytes!("../../../../resources/gatt_blocklist.txt")[..]
-            },
-            Resource::CrashHTML => &include_bytes!("../../../../resources/crash.html")[..],
-            Resource::DirectoryListingHTML => {
-                &include_bytes!("../../../../resources/directory-listing.html")[..]
-            },
-            Resource::AboutMemoryHTML => {
-                &include_bytes!("../../../../resources/about-memory.html")[..]
-            },
-            Resource::DebuggerJS => &include_bytes!("../../../../resources/debugger.js")[..],
-        })
-    }
-
-    fn sandbox_access_files(&self) -> Vec<PathBuf> {
-        vec![]
-    }
-
-    fn sandbox_access_files_dirs(&self) -> Vec<PathBuf> {
-        vec![]
-    }
-}

ports/servoshell/egl/ohos/mod.rs

@@ -102,7 +102,6 @@ use xcomponent_sys::{
 
 use super::app::{App, AppInitOptions, EmbeddedPlatformWindow, VsyncRefreshDriver};
 use super::host_trait::HostTrait;
-use crate::egl::ohos::resources::ResourceReaderInstance;
 use crate::prefs::{ArgumentParsingResult, parse_command_line_arguments};
 
 /// Queue length for the thread-safe function to submit URL updates to ArkTS
@@ -209,7 +208,7 @@ fn init_app(
 
     let resource_dir = PathBuf::from(&options.resource_dir).join("servo");
     debug!("Resources are located at: {:?}", resource_dir);
-    servo::resources::set(Box::new(ResourceReaderInstance::new(resource_dir.clone())));
+    resources::set_resource_dir(resource_dir.clone());
 
     let args = options
         .commandline_args

ports/servoshell/egl/ohos/resources.rs

@@ -3,24 +3,37 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 use std::fs;
 use std::path::PathBuf;
+use std::sync::OnceLock;
 
 use servo::resources::{Resource, ResourceReaderMethods};
 
-pub(crate) struct ResourceReaderInstance {
-    resource_dir: PathBuf,
+pub(crate) struct ResourceReaderImpl {
+    resource_dir: OnceLock<PathBuf>,
 }
 
-impl ResourceReaderInstance {
-    pub(crate) fn new(resource_dir: PathBuf) -> Self {
-        assert!(resource_dir.is_dir());
-        Self { resource_dir }
+static RESOURCE_READER: ResourceReaderImpl = ResourceReaderImpl {
+    resource_dir: OnceLock::new(),
+};
+
+servo::submit_resource_reader!(&RESOURCE_READER);
+
+pub(crate) fn set_resource_dir(resource_dir: PathBuf) {
+    if let Err(e) = RESOURCE_READER.resource_dir.set(resource_dir) {
+        log::warn!("Failed to set resource dir: {:?}", e);
     }
 }
 
-impl ResourceReaderMethods for ResourceReaderInstance {
+impl ResourceReaderMethods for ResourceReaderImpl {
     fn read(&self, res: Resource) -> Vec<u8> {
-        let file_path = self.resource_dir.join(res.filename());
-        fs::read(&file_path).expect("failed to read resource file")
+        let file_path = RESOURCE_READER
+            .resource_dir
+            .get()
+            .expect("Attempted to read resources before reader initialized")
+            .join("named_resources")
+            .join(res.filename());
+        fs::read(&file_path).unwrap_or_else(|e| {
+            panic!("Failed to read resource file: {:?}: {:?}", file_path, e);
+        })
     }
 
     fn sandbox_access_files(&self) -> Vec<PathBuf> {

ports/servoshell/lib.rs

@@ -19,7 +19,7 @@ mod egl;
 mod panic_hook;
 mod parser;
 mod prefs;
-#[cfg(not(target_os = "android"))]
+#[cfg(not(any(target_os = "android", target_env = "ohos")))]
 mod resources;
 mod running_app_state;
 mod webdriver;

ports/servoshell/resources/mod.rs

@@ -2,22 +2,19 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use std::env;
 use std::path::PathBuf;
 use std::sync::Mutex;
-use std::{env, fs};
 
 use cfg_if::cfg_if;
-use servo::resources::{self, Resource};
 
 static CMD_RESOURCE_DIR: Mutex<Option<PathBuf>> = Mutex::new(None);
 
-struct ResourceReader;
-
-pub fn init() {
-    resources::set(Box::new(ResourceReader));
+pub(crate) fn resource_protocol_dir_path() -> PathBuf {
+    resource_root_dir_path().join("resource_protocol")
 }
 
-pub(crate) fn resources_dir_path() -> PathBuf {
+fn resource_root_dir_path() -> PathBuf {
     // This needs to be called before the process is sandboxed
     // as we only give permission to read inside the resources directory,
     // not the permissions the "search" for the resources directory.
@@ -27,7 +24,7 @@ pub(crate) fn resources_dir_path() -> PathBuf {
     }
 
     // Try ./resources and ./Resources relative to the directory containing the
-    // canonicalised executable path, then each of its ancestors.
+    // canonicalized executable path, then each of its ancestors.
     let mut path = env::current_exe().unwrap().canonicalize().unwrap();
     while path.pop() {
         path.push("resources");
@@ -51,7 +48,7 @@ pub(crate) fn resources_dir_path() -> PathBuf {
             panic!("Can't find resources directory")
         } else {
             // Static assert that this is really a non-production build, rather
-            // than a failure of the build script’s production check.
+            // than a failure of the build script's production check.
             const _: () = assert!(cfg!(servo_do_not_use_in_production));
 
             // Try ./resources in the current directory, then each of its ancestors.
@@ -72,17 +69,3 @@ pub(crate) fn resources_dir_path() -> PathBuf {
         }
     }
 }
-
-impl resources::ResourceReaderMethods for ResourceReader {
-    fn read(&self, file: Resource) -> Vec<u8> {
-        let mut path = resources_dir_path();
-        path.push(file.filename());
-        fs::read(path).expect("Can't read file")
-    }
-    fn sandbox_access_files_dirs(&self) -> Vec<PathBuf> {
-        vec![resources_dir_path()]
-    }
-    fn sandbox_access_files(&self) -> Vec<PathBuf> {
-        vec![]
-    }
-}