introduce hir debugging infra

This is to make debugging rust-analyzer easier.

The idea is that `dbg!(krate.debug(db))` will print the actual, fuzzy
crate name, instead of precise ID. Debug printing infra is a separate
thing, to make sure that the actual hir doesn't have access to global
information.

Do not use `.debug` for `log::` logging: debugging executes queries,
and might introduce unneded dependencies to the crate graph

crates/ra_ide_api/src/change.rs

@@ -2,7 +2,7 @@ use std::{fmt, sync::Arc, time};
 
 use ra_db::{
     salsa::{Database, Durability, SweepStrategy},
-    CrateGraph, FileId, SourceDatabase, SourceRoot, SourceRootId,
+    CrateGraph, CrateId, FileId, SourceDatabase, SourceRoot, SourceRootId,
 };
 use ra_prof::{memory_usage, profile, Bytes};
 use ra_syntax::SourceFile;
@@ -11,7 +11,7 @@ use relative_path::RelativePathBuf;
 use rustc_hash::FxHashMap;
 
 use crate::{
-    db::RootDatabase,
+    db::{DebugData, RootDatabase},
     status::syntax_tree_stats,
     symbol_index::{SymbolIndex, SymbolsDatabase},
 };
@@ -23,6 +23,7 @@ pub struct AnalysisChange {
     files_changed: Vec<(FileId, Arc<String>)>,
     libraries_added: Vec<LibraryData>,
     crate_graph: Option<CrateGraph>,
+    debug_data: DebugData,
 }
 
 impl fmt::Debug for AnalysisChange {
@@ -83,6 +84,14 @@ impl AnalysisChange {
     pub fn set_crate_graph(&mut self, graph: CrateGraph) {
         self.crate_graph = Some(graph);
     }
+
+    pub fn set_debug_crate_name(&mut self, crate_id: CrateId, name: String) {
+        self.debug_data.crate_names.insert(crate_id, name);
+    }
+
+    pub fn set_debug_root_path(&mut self, source_root_id: SourceRootId, path: String) {
+        self.debug_data.root_paths.insert(source_root_id, path);
+    }
 }
 
 #[derive(Debug)]
@@ -200,6 +209,8 @@ impl RootDatabase {
         if let Some(crate_graph) = change.crate_graph {
             self.set_crate_graph_with_durability(Arc::new(crate_graph), Durability::HIGH)
         }
+
+        Arc::make_mut(&mut self.debug_data).merge(change.debug_data)
     }
 
     fn apply_root_change(&mut self, root_id: SourceRootId, root_change: RootChange) {

crates/ra_ide_api/src/db.rs

@@ -2,8 +2,9 @@ use std::{sync::Arc, time};
 
 use ra_db::{
     salsa::{self, Database, Durability},
-    Canceled, CheckCanceled, FileId, SourceDatabase,
+    Canceled, CheckCanceled, CrateId, FileId, SourceDatabase, SourceRootId,
 };
+use rustc_hash::FxHashMap;
 
 use crate::{
     symbol_index::{self, SymbolsDatabase},
@@ -23,10 +24,23 @@ use crate::{
 pub(crate) struct RootDatabase {
     runtime: salsa::Runtime<RootDatabase>,
     pub(crate) feature_flags: Arc<FeatureFlags>,
+    pub(crate) debug_data: Arc<DebugData>,
     pub(crate) last_gc: time::Instant,
     pub(crate) last_gc_check: time::Instant,
 }
 
+impl hir::debug::HirDebugHelper for RootDatabase {
+    fn crate_name(&self, krate: CrateId) -> Option<String> {
+        self.debug_data.crate_names.get(&krate).cloned()
+    }
+    fn file_path(&self, file_id: FileId) -> Option<String> {
+        let source_root_id = self.file_source_root(file_id);
+        let source_root_path = self.debug_data.root_paths.get(&source_root_id)?;
+        let file_path = self.file_relative_path(file_id);
+        Some(format!("{}/{}", source_root_path, file_path.display()))
+    }
+}
+
 impl salsa::Database for RootDatabase {
     fn salsa_runtime(&self) -> &salsa::Runtime<RootDatabase> {
         &self.runtime
@@ -58,6 +72,7 @@ impl RootDatabase {
             last_gc: time::Instant::now(),
             last_gc_check: time::Instant::now(),
             feature_flags: Arc::new(feature_flags),
+            debug_data: Default::default(),
         };
         db.set_crate_graph_with_durability(Default::default(), Durability::HIGH);
         db.set_local_roots_with_durability(Default::default(), Durability::HIGH);
@@ -77,6 +92,7 @@ impl salsa::ParallelDatabase for RootDatabase {
             last_gc: self.last_gc,
             last_gc_check: self.last_gc_check,
             feature_flags: Arc::clone(&self.feature_flags),
+            debug_data: Arc::clone(&self.debug_data),
         })
     }
 }
@@ -90,3 +106,16 @@ fn line_index(db: &impl ra_db::SourceDatabase, file_id: FileId) -> Arc<LineIndex
     let text = db.file_text(file_id);
     Arc::new(LineIndex::new(&*text))
 }
+
+#[derive(Debug, Default, Clone)]
+pub(crate) struct DebugData {
+    pub(crate) root_paths: FxHashMap<SourceRootId, String>,
+    pub(crate) crate_names: FxHashMap<CrateId, String>,
+}
+
+impl DebugData {
+    pub(crate) fn merge(&mut self, other: DebugData) {
+        self.root_paths.extend(other.root_paths.into_iter());
+        self.crate_names.extend(other.crate_names.into_iter());
+    }
+}