src/tools/rust-analyzer/crates/rust-analyzer/src/reload.rs

   1 //! Project loading & configuration updates.
   2 //!
   3 //! This is quite tricky. The main problem is time and changes -- there's no
   4 //! fixed "project" rust-analyzer is working with, "current project" is itself
   5 //! mutable state. For example, when the user edits `Cargo.toml` by adding a new
   6 //! dependency, project model changes. What's more, switching project model is
   7 //! not instantaneous -- it takes time to run `cargo metadata` and (for proc
   8 //! macros) `cargo check`.
   9 //!
  10 //! The main guiding principle here is, as elsewhere in rust-analyzer,
  11 //! robustness. We try not to assume that the project model exists or is
  12 //! correct. Instead, we try to provide a best-effort service. Even if the
  13 //! project is currently loading and we don't have a full project model, we
  14 //! still want to respond to various  requests.
  15 use std::{mem, sync::Arc};
  16
  17 use flycheck::{FlycheckConfig, FlycheckHandle};
  18 use hir::db::DefDatabase;
  19 use ide::Change;
  20 use ide_db::base_db::{
  21     CrateGraph, Env, ProcMacro, ProcMacroExpander, ProcMacroExpansionError, ProcMacroKind,
  22     ProcMacroLoadResult, SourceRoot, VfsPath,
  23 };
  24 use proc_macro_api::{MacroDylib, ProcMacroServer};
  25 use project_model::{ProjectWorkspace, WorkspaceBuildScripts};
  26 use syntax::SmolStr;
  27 use vfs::{file_set::FileSetConfig, AbsPath, AbsPathBuf, ChangeKind};
  28
  29 use crate::{
  30     config::{Config, FilesWatcher, LinkedProject},
  31     global_state::GlobalState,
  32     lsp_ext,
  33     main_loop::Task,
  34     op_queue::Cause,
  35 };
  36
  37 #[derive(Debug)]
  38 pub(crate) enum ProjectWorkspaceProgress {
  39     Begin,
  40     Report(String),
  41     End(Vec<anyhow::Result<ProjectWorkspace>>),
  42 }
  43
  44 #[derive(Debug)]
  45 pub(crate) enum BuildDataProgress {
  46     Begin,
  47     Report(String),
  48     End((Arc<Vec<ProjectWorkspace>>, Vec<anyhow::Result<WorkspaceBuildScripts>>)),
  49 }
  50
  51 impl GlobalState {
  52     pub(crate) fn is_quiescent(&self) -> bool {
  53         !(self.fetch_workspaces_queue.op_in_progress()
  54             || self.fetch_build_data_queue.op_in_progress()
  55             || self.vfs_progress_config_version < self.vfs_config_version
  56             || self.vfs_progress_n_done < self.vfs_progress_n_total)
  57     }
  58
  59     pub(crate) fn update_configuration(&mut self, config: Config) {
  60         let _p = profile::span("GlobalState::update_configuration");
  61         let old_config = mem::replace(&mut self.config, Arc::new(config));
  62         if self.config.lru_capacity() != old_config.lru_capacity() {
  63             self.analysis_host.update_lru_capacity(self.config.lru_capacity());
  64         }
  65         if self.config.linked_projects() != old_config.linked_projects() {
  66             self.fetch_workspaces_queue.request_op("linked projects changed".to_string())
  67         } else if self.config.flycheck() != old_config.flycheck() {
  68             self.reload_flycheck();
  69         }
  70
  71         if self.analysis_host.raw_database().enable_proc_attr_macros()
  72             != self.config.expand_proc_attr_macros()
  73         {
  74             self.analysis_host
  75                 .raw_database_mut()
  76                 .set_enable_proc_attr_macros(self.config.expand_proc_attr_macros());
  77         }
  78     }
  79
  80     pub(crate) fn current_status(&self) -> lsp_ext::ServerStatusParams {
  81         let mut status = lsp_ext::ServerStatusParams {
  82             health: lsp_ext::Health::Ok,
  83             quiescent: self.is_quiescent(),
  84             message: None,
  85         };
  86
  87         if self.proc_macro_changed {
  88             status.health = lsp_ext::Health::Warning;
  89             status.message =
  90                 Some("Reload required due to source changes of a procedural macro.".into())
  91         }
  92         if let Err(_) = self.fetch_build_data_error() {
  93             status.health = lsp_ext::Health::Warning;
  94             status.message =
  95                 Some("Failed to run build scripts of some packages, check the logs.".to_string());
  96         }
  97         if !self.config.cargo_autoreload()
  98             && self.is_quiescent()
  99             && self.fetch_workspaces_queue.op_requested()
 100         {
 101             status.health = lsp_ext::Health::Warning;
 102             status.message = Some("Workspace reload required".to_string())
 103         }
 104
 105         if let Err(error) = self.fetch_workspace_error() {
 106             status.health = lsp_ext::Health::Error;
 107             status.message = Some(error)
 108         }
 109         status
 110     }
 111
 112     pub(crate) fn fetch_workspaces(&mut self, cause: Cause) {
 113         tracing::info!(%cause, "will fetch workspaces");
 114
 115         self.task_pool.handle.spawn_with_sender({
 116             let linked_projects = self.config.linked_projects();
 117             let detached_files = self.config.detached_files().to_vec();
 118             let cargo_config = self.config.cargo();
 119
 120             move |sender| {
 121                 let progress = {
 122                     let sender = sender.clone();
 123                     move |msg| {
 124                         sender
 125                             .send(Task::FetchWorkspace(ProjectWorkspaceProgress::Report(msg)))
 126                             .unwrap()
 127                     }
 128                 };
 129
 130                 sender.send(Task::FetchWorkspace(ProjectWorkspaceProgress::Begin)).unwrap();
 131
 132                 let mut workspaces = linked_projects
 133                     .iter()
 134                     .map(|project| match project {
 135                         LinkedProject::ProjectManifest(manifest) => {
 136                             project_model::ProjectWorkspace::load(
 137                                 manifest.clone(),
 138                                 &cargo_config,
 139                                 &progress,
 140                             )
 141                         }
 142                         LinkedProject::InlineJsonProject(it) => {
 143                             project_model::ProjectWorkspace::load_inline(
 144                                 it.clone(),
 145                                 cargo_config.target.as_deref(),
 146                             )
 147                         }
 148                     })
 149                     .collect::<Vec<_>>();
 150
 151                 if !detached_files.is_empty() {
 152                     workspaces
 153                         .push(project_model::ProjectWorkspace::load_detached_files(detached_files));
 154                 }
 155
 156                 tracing::info!("did fetch workspaces {:?}", workspaces);
 157                 sender
 158                     .send(Task::FetchWorkspace(ProjectWorkspaceProgress::End(workspaces)))
 159                     .unwrap();
 160             }
 161         });
 162     }
 163
 164     pub(crate) fn fetch_build_data(&mut self, cause: Cause) {
 165         tracing::info!(%cause, "will fetch build data");
 166         let workspaces = Arc::clone(&self.workspaces);
 167         let config = self.config.cargo();
 168         self.task_pool.handle.spawn_with_sender(move |sender| {
 169             sender.send(Task::FetchBuildData(BuildDataProgress::Begin)).unwrap();
 170
 171             let progress = {
 172                 let sender = sender.clone();
 173                 move |msg| {
 174                     sender.send(Task::FetchBuildData(BuildDataProgress::Report(msg))).unwrap()
 175                 }
 176             };
 177             let mut res = Vec::new();
 178             for ws in workspaces.iter() {
 179                 res.push(ws.run_build_scripts(&config, &progress));
 180             }
 181             sender.send(Task::FetchBuildData(BuildDataProgress::End((workspaces, res)))).unwrap();
 182         });
 183     }
 184
 185     pub(crate) fn switch_workspaces(&mut self, cause: Cause) {
 186         let _p = profile::span("GlobalState::switch_workspaces");
 187         tracing::info!(%cause, "will switch workspaces");
 188
 189         if let Err(error_message) = self.fetch_workspace_error() {
 190             self.show_and_log_error(error_message, None);
 191             if !self.workspaces.is_empty() {
 192                 // It only makes sense to switch to a partially broken workspace
 193                 // if we don't have any workspace at all yet.
 194                 return;
 195             }
 196         }
 197
 198         if let Err(error) = self.fetch_build_data_error() {
 199             self.show_and_log_error("failed to run build scripts".to_string(), Some(error));
 200         }
 201
 202         let workspaces = self
 203             .fetch_workspaces_queue
 204             .last_op_result()
 205             .iter()
 206             .filter_map(|res| res.as_ref().ok().cloned())
 207             .collect::<Vec<_>>();
 208
 209         fn eq_ignore_build_data<'a>(
 210             left: &'a ProjectWorkspace,
 211             right: &'a ProjectWorkspace,
 212         ) -> bool {
 213             let key = |p: &'a ProjectWorkspace| match p {
 214                 ProjectWorkspace::Cargo {
 215                     cargo,
 216                     sysroot,
 217                     rustc,
 218                     rustc_cfg,
 219                     cfg_overrides,
 220
 221                     build_scripts: _,
 222                     toolchain: _,
 223                 } => Some((cargo, sysroot, rustc, rustc_cfg, cfg_overrides)),
 224                 _ => None,
 225             };
 226             match (key(left), key(right)) {
 227                 (Some(lk), Some(rk)) => lk == rk,
 228                 _ => left == right,
 229             }
 230         }
 231
 232         let same_workspaces = workspaces.len() == self.workspaces.len()
 233             && workspaces
 234                 .iter()
 235                 .zip(self.workspaces.iter())
 236                 .all(|(l, r)| eq_ignore_build_data(l, r));
 237
 238         if same_workspaces {
 239             let (workspaces, build_scripts) = self.fetch_build_data_queue.last_op_result();
 240             if Arc::ptr_eq(workspaces, &self.workspaces) {
 241                 tracing::debug!("set build scripts to workspaces");
 242
 243                 let workspaces = workspaces
 244                     .iter()
 245                     .cloned()
 246                     .zip(build_scripts)
 247                     .map(|(mut ws, bs)| {
 248                         ws.set_build_scripts(bs.as_ref().ok().cloned().unwrap_or_default());
 249                         ws
 250                     })
 251                     .collect::<Vec<_>>();
 252
 253                 // Workspaces are the same, but we've updated build data.
 254                 self.workspaces = Arc::new(workspaces);
 255             } else {
 256                 tracing::info!("build scripts do not match the version of the active workspace");
 257                 // Current build scripts do not match the version of the active
 258                 // workspace, so there's nothing for us to update.
 259                 return;
 260             }
 261         } else {
 262             tracing::debug!("abandon build scripts for workspaces");
 263
 264             // Here, we completely changed the workspace (Cargo.toml edit), so
 265             // we don't care about build-script results, they are stale.
 266             self.workspaces = Arc::new(workspaces)
 267         }
 268
 269         if let FilesWatcher::Client = self.config.files().watcher {
 270             let registration_options = lsp_types::DidChangeWatchedFilesRegistrationOptions {
 271                 watchers: self
 272                     .workspaces
 273                     .iter()
 274                     .flat_map(|ws| ws.to_roots())
 275                     .filter(|it| it.is_local)
 276                     .flat_map(|root| {
 277                         root.include.into_iter().flat_map(|it| {
 278                             [
 279                                 format!("{}/**/*.rs", it.display()),
 280                                 format!("{}/**/Cargo.toml", it.display()),
 281                                 format!("{}/**/Cargo.lock", it.display()),
 282                             ]
 283                         })
 284                     })
 285                     .map(|glob_pattern| lsp_types::FileSystemWatcher { glob_pattern, kind: None })
 286                     .collect(),
 287             };
 288             let registration = lsp_types::Registration {
 289                 id: "workspace/didChangeWatchedFiles".to_string(),
 290                 method: "workspace/didChangeWatchedFiles".to_string(),
 291                 register_options: Some(serde_json::to_value(registration_options).unwrap()),
 292             };
 293             self.send_request::<lsp_types::request::RegisterCapability>(
 294                 lsp_types::RegistrationParams { registrations: vec![registration] },
 295                 |_, _| (),
 296             );
 297         }
 298
 299         let mut change = Change::new();
 300
 301         let files_config = self.config.files();
 302         let project_folders = ProjectFolders::new(&self.workspaces, &files_config.exclude);
 303
 304         let standalone_server_name =
 305             format!("rust-analyzer-proc-macro-srv{}", std::env::consts::EXE_SUFFIX);
 306
 307         if self.proc_macro_clients.is_empty() {
 308             if let Some((path, args)) = self.config.proc_macro_srv() {
 309                 tracing::info!("Spawning proc-macro servers");
 310                 self.proc_macro_clients = self
 311                     .workspaces
 312                     .iter()
 313                     .map(|ws| {
 314                         let mut args = args.clone();
 315                         let mut path = path.clone();
 316
 317                         if let ProjectWorkspace::Cargo { sysroot, .. } = ws {
 318                             tracing::debug!("Found a cargo workspace...");
 319                             if let Some(sysroot) = sysroot.as_ref() {
 320                                 tracing::debug!("Found a cargo workspace with a sysroot...");
 321                                 let server_path =
 322                                     sysroot.root().join("libexec").join(&standalone_server_name);
 323                                 if std::fs::metadata(&server_path).is_ok() {
 324                                     tracing::debug!(
 325                                         "And the server exists at {}",
 326                                         server_path.display()
 327                                     );
 328                                     path = server_path;
 329                                     args = vec![];
 330                                 } else {
 331                                     tracing::debug!(
 332                                         "And the server does not exist at {}",
 333                                         server_path.display()
 334                                     );
 335                                 }
 336                             }
 337                         }
 338
 339                         tracing::info!(?args, "Using proc-macro server at {}", path.display(),);
 340                         ProcMacroServer::spawn(path.clone(), args.clone()).map_err(|err| {
 341                             let error = format!(
 342                                 "Failed to run proc-macro server from path {}, error: {:?}",
 343                                 path.display(),
 344                                 err
 345                             );
 346                             tracing::error!(error);
 347                             error
 348                         })
 349                     })
 350                     .collect()
 351             };
 352         }
 353
 354         let watch = match files_config.watcher {
 355             FilesWatcher::Client => vec![],
 356             FilesWatcher::Server => project_folders.watch,
 357         };
 358         self.vfs_config_version += 1;
 359         self.loader.handle.set_config(vfs::loader::Config {
 360             load: project_folders.load,
 361             watch,
 362             version: self.vfs_config_version,
 363         });
 364
 365         // Create crate graph from all the workspaces
 366         let crate_graph = {
 367             let dummy_replacements = self.config.dummy_replacements();
 368
 369             let vfs = &mut self.vfs.write().0;
 370             let loader = &mut self.loader;
 371             let mem_docs = &self.mem_docs;
 372             let mut load = move |path: &AbsPath| {
 373                 let _p = profile::span("GlobalState::load");
 374                 let vfs_path = vfs::VfsPath::from(path.to_path_buf());
 375                 if !mem_docs.contains(&vfs_path) {
 376                     let contents = loader.handle.load_sync(path);
 377                     vfs.set_file_contents(vfs_path.clone(), contents);
 378                 }
 379                 let res = vfs.file_id(&vfs_path);
 380                 if res.is_none() {
 381                     tracing::warn!("failed to load {}", path.display())
 382                 }
 383                 res
 384             };
 385
 386             let mut crate_graph = CrateGraph::default();
 387             for (idx, ws) in self.workspaces.iter().enumerate() {
 388                 let proc_macro_client = match self.proc_macro_clients.get(idx) {
 389                     Some(res) => res.as_ref().map_err(|e| &**e),
 390                     None => Err("Proc macros are disabled"),
 391                 };
 392                 let mut load_proc_macro = move |crate_name: &str, path: &AbsPath| {
 393                     load_proc_macro(
 394                         proc_macro_client,
 395                         path,
 396                         dummy_replacements.get(crate_name).map(|v| &**v).unwrap_or_default(),
 397                     )
 398                 };
 399                 crate_graph.extend(ws.to_crate_graph(&mut load_proc_macro, &mut load));
 400             }
 401             crate_graph
 402         };
 403         change.set_crate_graph(crate_graph);
 404
 405         self.source_root_config = project_folders.source_root_config;
 406
 407         self.analysis_host.apply_change(change);
 408         self.process_changes();
 409         self.reload_flycheck();
 410         tracing::info!("did switch workspaces");
 411     }
 412
 413     fn fetch_workspace_error(&self) -> Result<(), String> {
 414         let mut buf = String::new();
 415
 416         for ws in self.fetch_workspaces_queue.last_op_result() {
 417             if let Err(err) = ws {
 418                 stdx::format_to!(buf, "rust-analyzer failed to load workspace: {:#}\n", err);
 419             }
 420         }
 421
 422         if buf.is_empty() {
 423             return Ok(());
 424         }
 425
 426         Err(buf)
 427     }
 428
 429     fn fetch_build_data_error(&self) -> Result<(), String> {
 430         let mut buf = String::new();
 431
 432         for ws in &self.fetch_build_data_queue.last_op_result().1 {
 433             match ws {
 434                 Ok(data) => match data.error() {
 435                     Some(stderr) => stdx::format_to!(buf, "{:#}\n", stderr),
 436                     _ => (),
 437                 },
 438                 // io errors
 439                 Err(err) => stdx::format_to!(buf, "{:#}\n", err),
 440             }
 441         }
 442
 443         if buf.is_empty() {
 444             Ok(())
 445         } else {
 446             Err(buf)
 447         }
 448     }
 449
 450     fn reload_flycheck(&mut self) {
 451         let _p = profile::span("GlobalState::reload_flycheck");
 452         let config = match self.config.flycheck() {
 453             Some(it) => it,
 454             None => {
 455                 self.flycheck = Vec::new();
 456                 self.diagnostics.clear_check_all();
 457                 return;
 458             }
 459         };
 460
 461         let sender = self.flycheck_sender.clone();
 462         self.flycheck = self
 463             .workspaces
 464             .iter()
 465             .enumerate()
 466             .filter_map(|(id, w)| match w {
 467                 ProjectWorkspace::Cargo { cargo, .. } => Some((id, cargo.workspace_root())),
 468                 ProjectWorkspace::Json { project, .. } => {
 469                     // Enable flychecks for json projects if a custom flycheck command was supplied
 470                     // in the workspace configuration.
 471                     match config {
 472                         FlycheckConfig::CustomCommand { .. } => Some((id, project.path())),
 473                         _ => None,
 474                     }
 475                 }
 476                 ProjectWorkspace::DetachedFiles { .. } => None,
 477             })
 478             .map(|(id, root)| {
 479                 let sender = sender.clone();
 480                 FlycheckHandle::spawn(
 481                     id,
 482                     Box::new(move |msg| sender.send(msg).unwrap()),
 483                     config.clone(),
 484                     root.to_path_buf(),
 485                 )
 486             })
 487             .collect();
 488     }
 489 }
 490
 491 #[derive(Default)]
 492 pub(crate) struct ProjectFolders {
 493     pub(crate) load: Vec<vfs::loader::Entry>,
 494     pub(crate) watch: Vec<usize>,
 495     pub(crate) source_root_config: SourceRootConfig,
 496 }
 497
 498 impl ProjectFolders {
 499     pub(crate) fn new(
 500         workspaces: &[ProjectWorkspace],
 501         global_excludes: &[AbsPathBuf],
 502     ) -> ProjectFolders {
 503         let mut res = ProjectFolders::default();
 504         let mut fsc = FileSetConfig::builder();
 505         let mut local_filesets = vec![];
 506
 507         for root in workspaces.iter().flat_map(|ws| ws.to_roots()) {
 508             let file_set_roots: Vec<VfsPath> =
 509                 root.include.iter().cloned().map(VfsPath::from).collect();
 510
 511             let entry = {
 512                 let mut dirs = vfs::loader::Directories::default();
 513                 dirs.extensions.push("rs".into());
 514                 dirs.include.extend(root.include);
 515                 dirs.exclude.extend(root.exclude);
 516                 for excl in global_excludes {
 517                     if dirs
 518                         .include
 519                         .iter()
 520                         .any(|incl| incl.starts_with(excl) || excl.starts_with(incl))
 521                     {
 522                         dirs.exclude.push(excl.clone());
 523                     }
 524                 }
 525
 526                 vfs::loader::Entry::Directories(dirs)
 527             };
 528
 529             if root.is_local {
 530                 res.watch.push(res.load.len());
 531             }
 532             res.load.push(entry);
 533
 534             if root.is_local {
 535                 local_filesets.push(fsc.len());
 536             }
 537             fsc.add_file_set(file_set_roots)
 538         }
 539
 540         let fsc = fsc.build();
 541         res.source_root_config = SourceRootConfig { fsc, local_filesets };
 542
 543         res
 544     }
 545 }
 546
 547 #[derive(Default, Debug)]
 548 pub(crate) struct SourceRootConfig {
 549     pub(crate) fsc: FileSetConfig,
 550     pub(crate) local_filesets: Vec<usize>,
 551 }
 552
 553 impl SourceRootConfig {
 554     pub(crate) fn partition(&self, vfs: &vfs::Vfs) -> Vec<SourceRoot> {
 555         let _p = profile::span("SourceRootConfig::partition");
 556         self.fsc
 557             .partition(vfs)
 558             .into_iter()
 559             .enumerate()
 560             .map(|(idx, file_set)| {
 561                 let is_local = self.local_filesets.contains(&idx);
 562                 if is_local {
 563                     SourceRoot::new_local(file_set)
 564                 } else {
 565                     SourceRoot::new_library(file_set)
 566                 }
 567             })
 568             .collect()
 569     }
 570 }
 571
 572 /// Load the proc-macros for the given lib path, replacing all expanders whose names are in `dummy_replace`
 573 /// with an identity dummy expander.
 574 pub(crate) fn load_proc_macro(
 575     server: Result<&ProcMacroServer, &str>,
 576     path: &AbsPath,
 577     dummy_replace: &[Box<str>],
 578 ) -> ProcMacroLoadResult {
 579     let res: Result<Vec<_>, String> = (|| {
 580         let dylib = MacroDylib::new(path.to_path_buf())
 581             .map_err(|io| format!("Proc-macro dylib loading failed: {io}"))?;
 582         let server = server.map_err(ToOwned::to_owned)?;
 583         let vec = server.load_dylib(dylib).map_err(|e| format!("{e}"))?;
 584         if vec.is_empty() {
 585             return Err("proc macro library returned no proc macros".to_string());
 586         }
 587         Ok(vec
 588             .into_iter()
 589             .map(|expander| expander_to_proc_macro(expander, dummy_replace))
 590             .collect())
 591     })();
 592     return match res {
 593         Ok(proc_macros) => {
 594             tracing::info!(
 595                 "Loaded proc-macros for {}: {:?}",
 596                 path.display(),
 597                 proc_macros.iter().map(|it| it.name.clone()).collect::<Vec<_>>()
 598             );
 599             Ok(proc_macros)
 600         }
 601         Err(e) => {
 602             tracing::warn!("proc-macro loading for {} failed: {e}", path.display());
 603             Err(e)
 604         }
 605     };
 606
 607     fn expander_to_proc_macro(
 608         expander: proc_macro_api::ProcMacro,
 609         dummy_replace: &[Box<str>],
 610     ) -> ProcMacro {
 611         let name = SmolStr::from(expander.name());
 612         let kind = match expander.kind() {
 613             proc_macro_api::ProcMacroKind::CustomDerive => ProcMacroKind::CustomDerive,
 614             proc_macro_api::ProcMacroKind::FuncLike => ProcMacroKind::FuncLike,
 615             proc_macro_api::ProcMacroKind::Attr => ProcMacroKind::Attr,
 616         };
 617         let expander: Arc<dyn ProcMacroExpander> =
 618             if dummy_replace.iter().any(|replace| &**replace == name) {
 619                 match kind {
 620                     ProcMacroKind::Attr => Arc::new(IdentityExpander),
 621                     _ => Arc::new(EmptyExpander),
 622                 }
 623             } else {
 624                 Arc::new(Expander(expander))
 625             };
 626         ProcMacro { name, kind, expander }
 627     }
 628
 629     #[derive(Debug)]
 630     struct Expander(proc_macro_api::ProcMacro);
 631
 632     impl ProcMacroExpander for Expander {
 633         fn expand(
 634             &self,
 635             subtree: &tt::Subtree,
 636             attrs: Option<&tt::Subtree>,
 637             env: &Env,
 638         ) -> Result<tt::Subtree, ProcMacroExpansionError> {
 639             let env = env.iter().map(|(k, v)| (k.to_string(), v.to_string())).collect();
 640             match self.0.expand(subtree, attrs, env) {
 641                 Ok(Ok(subtree)) => Ok(subtree),
 642                 Ok(Err(err)) => Err(ProcMacroExpansionError::Panic(err.0)),
 643                 Err(err) => Err(ProcMacroExpansionError::System(err.to_string())),
 644             }
 645         }
 646     }
 647
 648     /// Dummy identity expander, used for attribute proc-macros that are deliberately ignored by the user.
 649     #[derive(Debug)]
 650     struct IdentityExpander;
 651
 652     impl ProcMacroExpander for IdentityExpander {
 653         fn expand(
 654             &self,
 655             subtree: &tt::Subtree,
 656             _: Option<&tt::Subtree>,
 657             _: &Env,
 658         ) -> Result<tt::Subtree, ProcMacroExpansionError> {
 659             Ok(subtree.clone())
 660         }
 661     }
 662
 663     /// Empty expander, used for proc-macros that are deliberately ignored by the user.
 664     #[derive(Debug)]
 665     struct EmptyExpander;
 666
 667     impl ProcMacroExpander for EmptyExpander {
 668         fn expand(
 669             &self,
 670             _: &tt::Subtree,
 671             _: Option<&tt::Subtree>,
 672             _: &Env,
 673         ) -> Result<tt::Subtree, ProcMacroExpansionError> {
 674             Ok(tt::Subtree::default())
 675         }
 676     }
 677 }
 678
 679 pub(crate) fn should_refresh_for_change(path: &AbsPath, change_kind: ChangeKind) -> bool {
 680     const IMPLICIT_TARGET_FILES: &[&str] = &["build.rs", "src/main.rs", "src/lib.rs"];
 681     const IMPLICIT_TARGET_DIRS: &[&str] = &["src/bin", "examples", "tests", "benches"];
 682
 683     let file_name = match path.file_name().unwrap_or_default().to_str() {
 684         Some(it) => it,
 685         None => return false,
 686     };
 687
 688     if let "Cargo.toml" | "Cargo.lock" = file_name {
 689         return true;
 690     }
 691     if change_kind == ChangeKind::Modify {
 692         return false;
 693     }
 694
 695     // .cargo/config{.toml}
 696     if path.extension().unwrap_or_default() != "rs" {
 697         let is_cargo_config = matches!(file_name, "config.toml" | "config")
 698             && path.parent().map(|parent| parent.as_ref().ends_with(".cargo")).unwrap_or(false);
 699         return is_cargo_config;
 700     }
 701
 702     if IMPLICIT_TARGET_FILES.iter().any(|it| path.as_ref().ends_with(it)) {
 703         return true;
 704     }
 705     let parent = match path.parent() {
 706         Some(it) => it,
 707         None => return false,
 708     };
 709     if IMPLICIT_TARGET_DIRS.iter().any(|it| parent.as_ref().ends_with(it)) {
 710         return true;
 711     }
 712     if file_name == "main.rs" {
 713         let grand_parent = match parent.parent() {
 714             Some(it) => it,
 715             None => return false,
 716         };
 717         if IMPLICIT_TARGET_DIRS.iter().any(|it| grand_parent.as_ref().ends_with(it)) {
 718             return true;
 719         }
 720     }
 721     false
 722 }