8 files changed, 132 insertions, 22 deletions

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index b7f50b714..776613c7c 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -800,6 +800,10 @@ impl HirDisplay for &Ty {
 
 impl HirDisplay for ApplicationTy {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+        if f.should_truncate() {
+            return write!(f, "…");
+        }
+
         match self.ctor {
             TypeCtor::Bool => write!(f, "bool")?,
             TypeCtor::Char => write!(f, "char")?,
@@ -901,6 +905,10 @@ impl HirDisplay for ApplicationTy {
 
 impl HirDisplay for ProjectionTy {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+        if f.should_truncate() {
+            return write!(f, "…");
+        }
+
         let trait_name = self
             .associated_ty
             .parent_trait(f.db)
@@ -919,6 +927,10 @@ impl HirDisplay for ProjectionTy {
 
 impl HirDisplay for Ty {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+        if f.should_truncate() {
+            return write!(f, "…");
+        }
+
         match self {
             Ty::Apply(a_ty) => a_ty.hir_fmt(f)?,
             Ty::Projection(p_ty) => p_ty.hir_fmt(f)?,
@@ -1001,6 +1013,10 @@ impl HirDisplay for Ty {
 
 impl TraitRef {
     fn hir_fmt_ext(&self, f: &mut HirFormatter<impl HirDatabase>, use_as: bool) -> fmt::Result {
+        if f.should_truncate() {
+            return write!(f, "…");
+        }
+
         self.substs[0].hir_fmt(f)?;
         if use_as {
             write!(f, " as ")?;
@@ -1031,6 +1047,10 @@ impl HirDisplay for &GenericPredicate {
 
 impl HirDisplay for GenericPredicate {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result {
+        if f.should_truncate() {
+            return write!(f, "…");
+        }
+
         match self {
             GenericPredicate::Implemented(trait_ref) => trait_ref.hir_fmt(f)?,
             GenericPredicate::Projection(projection_pred) => {
diff --git a/crates/ra_hir/src/ty/display.rs b/crates/ra_hir/src/ty/display.rs
index 7910429d7..9bb3ece6c 100644
--- a/crates/ra_hir/src/ty/display.rs
+++ b/crates/ra_hir/src/ty/display.rs
@@ -7,15 +7,30 @@ use crate::db::HirDatabase;
 pub struct HirFormatter<'a, 'b, DB> {
     pub db: &'a DB,
     fmt: &'a mut fmt::Formatter<'b>,
+    buf: String,
+    curr_size: usize,
+    max_size: Option<usize>,
 }
 
 pub trait HirDisplay {
     fn hir_fmt(&self, f: &mut HirFormatter<impl HirDatabase>) -> fmt::Result;
+
     fn display<'a, DB>(&'a self, db: &'a DB) -> HirDisplayWrapper<'a, DB, Self>
     where
         Self: Sized,
     {
-        HirDisplayWrapper(db, self)
+        HirDisplayWrapper(db, self, None)
+    }
+
+    fn display_truncated<'a, DB>(
+        &'a self,
+        db: &'a DB,
+        max_size: Option<usize>,
+    ) -> HirDisplayWrapper<'a, DB, Self>
+    where
+        Self: Sized,
+    {
+        HirDisplayWrapper(db, self, max_size)
     }
 }
 
@@ -41,11 +56,25 @@ where
 
     /// This allows using the `write!` macro directly with a `HirFormatter`.
     pub fn write_fmt(&mut self, args: fmt::Arguments) -> fmt::Result {
-        fmt::write(self.fmt, args)
+        // We write to a buffer first to track output size
+        self.buf.clear();
+        fmt::write(&mut self.buf, args)?;
+        self.curr_size += self.buf.len();
+
+        // Then we write to the internal formatter from the buffer
+        self.fmt.write_str(&self.buf)
+    }
+
+    pub fn should_truncate(&self) -> bool {
+        if let Some(max_size) = self.max_size {
+            self.curr_size >= max_size
+        } else {
+            false
+        }
     }
 }
 
-pub struct HirDisplayWrapper<'a, DB, T>(&'a DB, &'a T);
+pub struct HirDisplayWrapper<'a, DB, T>(&'a DB, &'a T, Option<usize>);
 
 impl<'a, DB, T> fmt::Display for HirDisplayWrapper<'a, DB, T>
 where
@@ -53,6 +82,12 @@ where
     T: HirDisplay,
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        self.1.hir_fmt(&mut HirFormatter { db: self.0, fmt: f })
+        self.1.hir_fmt(&mut HirFormatter {
+            db: self.0,
+            fmt: f,
+            buf: String::with_capacity(20),
+            curr_size: 0,
+            max_size: self.2,
+        })
     }
 }
diff --git a/crates/ra_ide_api/src/inlay_hints.rs b/crates/ra_ide_api/src/inlay_hints.rs
index 0cd959848..24a7ca5e7 100644
--- a/crates/ra_ide_api/src/inlay_hints.rs
+++ b/crates/ra_ide_api/src/inlay_hints.rs
@@ -19,10 +19,15 @@ pub struct InlayHint {
     pub label: SmolStr,
 }
 
-pub(crate) fn inlay_hints(db: &RootDatabase, file_id: FileId, file: &SourceFile) -> Vec<InlayHint> {
+pub(crate) fn inlay_hints(
+    db: &RootDatabase,
+    file_id: FileId,
+    file: &SourceFile,
+    max_inlay_hint_length: Option<usize>,
+) -> Vec<InlayHint> {
     file.syntax()
         .descendants()
-        .map(|node| get_inlay_hints(db, file_id, &node).unwrap_or_default())
+        .map(|node| get_inlay_hints(db, file_id, &node, max_inlay_hint_length).unwrap_or_default())
         .flatten()
         .collect()
 }
@@ -31,6 +36,7 @@ fn get_inlay_hints(
     db: &RootDatabase,
     file_id: FileId,
     node: &SyntaxNode,
+    max_inlay_hint_length: Option<usize>,
 ) -> Option<Vec<InlayHint>> {
     let analyzer = SourceAnalyzer::new(db, hir::Source::new(file_id.into(), node), None);
     match_ast! {
@@ -40,7 +46,7 @@ fn get_inlay_hints(
                     return None;
                 }
                 let pat = it.pat()?;
-                Some(get_pat_type_hints(db, &analyzer, pat, false))
+                Some(get_pat_type_hints(db, &analyzer, pat, false, max_inlay_hint_length))
             },
             ast::LambdaExpr(it) => {
                 it.param_list().map(|param_list| {
@@ -48,22 +54,22 @@ fn get_inlay_hints(
                         .params()
                         .filter(|closure_param| closure_param.ascribed_type().is_none())
                         .filter_map(|closure_param| closure_param.pat())
-                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, false))
+                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, false, max_inlay_hint_length))
                         .flatten()
                         .collect()
                 })
             },
             ast::ForExpr(it) => {
                 let pat = it.pat()?;
-                Some(get_pat_type_hints(db, &analyzer, pat, false))
+                Some(get_pat_type_hints(db, &analyzer, pat, false, max_inlay_hint_length))
             },
             ast::IfExpr(it) => {
                 let pat = it.condition()?.pat()?;
-                Some(get_pat_type_hints(db, &analyzer, pat, true))
+                Some(get_pat_type_hints(db, &analyzer, pat, true, max_inlay_hint_length))
             },
             ast::WhileExpr(it) => {
                 let pat = it.condition()?.pat()?;
-                Some(get_pat_type_hints(db, &analyzer, pat, true))
+                Some(get_pat_type_hints(db, &analyzer, pat, true, max_inlay_hint_length))
             },
             ast::MatchArmList(it) => {
                 Some(
@@ -71,7 +77,7 @@ fn get_inlay_hints(
                         .arms()
                         .map(|match_arm| match_arm.pats())
                         .flatten()
-                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, true))
+                        .map(|root_pat| get_pat_type_hints(db, &analyzer, root_pat, true, max_inlay_hint_length))
                         .flatten()
                         .collect(),
                 )
@@ -86,6 +92,7 @@ fn get_pat_type_hints(
     analyzer: &SourceAnalyzer,
     root_pat: ast::Pat,
     skip_root_pat_hint: bool,
+    max_inlay_hint_length: Option<usize>,
 ) -> Vec<InlayHint> {
     let original_pat = &root_pat.clone();
 
@@ -99,7 +106,7 @@ fn get_pat_type_hints(
         .map(|(range, pat_type)| InlayHint {
             range,
             kind: InlayKind::TypeHint,
-            label: pat_type.display(db).to_string().into(),
+            label: pat_type.display_truncated(db, max_inlay_hint_length).to_string().into(),
         })
         .collect()
 }
@@ -209,7 +216,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
         [
             InlayHint {
                 range: [193; 197),
@@ -278,7 +285,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
         [
             InlayHint {
                 range: [21; 30),
@@ -307,7 +314,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
         [
             InlayHint {
                 range: [21; 30),
@@ -355,7 +362,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
         [
             InlayHint {
                 range: [166; 170),
@@ -418,7 +425,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
         [
             InlayHint {
                 range: [166; 170),
@@ -481,7 +488,7 @@ fn main() {
 }"#,
         );
 
-        assert_debug_snapshot!(analysis.inlay_hints(file_id).unwrap(), @r###"
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, None).unwrap(), @r###"
         [
             InlayHint {
                 range: [311; 315),
@@ -507,4 +514,41 @@ fn main() {
         "###
         );
     }
+
+    #[test]
+    fn hint_truncation() {
+        let (analysis, file_id) = single_file(
+            r#"
+struct Smol<T>(T);
+
+struct VeryLongOuterName<T>(T);
+
+fn main() {
+    let a = Smol(0u32);
+    let b = VeryLongOuterName(0usize);
+    let c = Smol(Smol(0u32))
+}"#,
+        );
+
+        assert_debug_snapshot!(analysis.inlay_hints(file_id, Some(8)).unwrap(), @r###"
+        [
+            InlayHint {
+                range: [74; 75),
+                kind: TypeHint,
+                label: "Smol<u32>",
+            },
+            InlayHint {
+                range: [98; 99),
+                kind: TypeHint,
+                label: "VeryLongOuterName<…>",
+            },
+            InlayHint {
+                range: [137; 138),
+                kind: TypeHint,
+                label: "Smol<Smol<…>>",
+            },
+        ]
+        "###
+        );
+    }
 }
diff --git a/crates/ra_ide_api/src/lib.rs b/crates/ra_ide_api/src/lib.rs
index 57ed97147..62ad996bc 100644
--- a/crates/ra_ide_api/src/lib.rs
+++ b/crates/ra_ide_api/src/lib.rs
@@ -344,8 +344,14 @@ impl Analysis {
     }
 
     /// Returns a list of the places in the file where type hints can be displayed.
-    pub fn inlay_hints(&self, file_id: FileId) -> Cancelable<Vec<InlayHint>> {
-        self.with_db(|db| inlay_hints::inlay_hints(db, file_id, &db.parse(file_id).tree()))
+    pub fn inlay_hints(
+        &self,
+        file_id: FileId,
+        max_inlay_hint_length: Option<usize>,
+    ) -> Cancelable<Vec<InlayHint>> {
+        self.with_db(|db| {
+            inlay_hints::inlay_hints(db, file_id, &db.parse(file_id).tree(), max_inlay_hint_length)
+        })
     }
 
     /// Returns the set of folding ranges.
diff --git a/crates/ra_lsp_server/src/config.rs b/crates/ra_lsp_server/src/config.rs
index 9871a3b37..8045f3d60 100644
--- a/crates/ra_lsp_server/src/config.rs
+++ b/crates/ra_lsp_server/src/config.rs
@@ -29,6 +29,8 @@ pub struct ServerConfig {
 
     pub lru_capacity: Option<usize>,
 
+    pub max_inlay_hint_length: Option<usize>,
+
     /// For internal usage to make integrated tests faster.
     #[serde(deserialize_with = "nullable_bool_true")]
     pub with_sysroot: bool,
@@ -44,6 +46,7 @@ impl Default for ServerConfig {
             exclude_globs: Vec::new(),
             use_client_watching: false,
             lru_capacity: None,
+            max_inlay_hint_length: None,
             with_sysroot: true,
             feature_flags: FxHashMap::default(),
         }
diff --git a/crates/ra_lsp_server/src/main_loop.rs b/crates/ra_lsp_server/src/main_loop.rs
index f828efdee..0dc0aeee8 100644
--- a/crates/ra_lsp_server/src/main_loop.rs
+++ b/crates/ra_lsp_server/src/main_loop.rs
@@ -123,6 +123,7 @@ pub fn main_loop(
                     .and_then(|it| it.folding_range.as_ref())
                     .and_then(|it| it.line_folding_only)
                     .unwrap_or(false),
+                max_inlay_hint_length: config.max_inlay_hint_length,
             }
         };
 
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 0461bf385..e552f2106 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -888,7 +888,7 @@ pub fn handle_inlay_hints(
     let analysis = world.analysis();
     let line_index = analysis.file_line_index(file_id)?;
     Ok(analysis
-        .inlay_hints(file_id)?
+        .inlay_hints(file_id, world.options.max_inlay_hint_length)?
         .into_iter()
         .map(|api_type| InlayHint {
             label: api_type.label.to_string(),
diff --git a/crates/ra_lsp_server/src/world.rs b/crates/ra_lsp_server/src/world.rs
index 51824e7a3..9bdea70c7 100644
--- a/crates/ra_lsp_server/src/world.rs
+++ b/crates/ra_lsp_server/src/world.rs
@@ -28,6 +28,7 @@ pub struct Options {
     pub publish_decorations: bool,
     pub supports_location_link: bool,
     pub line_folding_only: bool,
+    pub max_inlay_hint_length: Option<usize>,
 }
 
 /// `WorldState` is the primary mutable state of the language server