Move type inlay hint truncation to language server

This commit implements a general truncation framework for HirFormatter
that keeps track of how much has been output so far. This information
can then be used to perform truncation inside the language server,
instead of relying on the client.

Initial support is implemented for truncating types hints using the
maxInlayHintLength server config option. The existing solution in the
VSCode extension has been removed in favor of letting the server
truncate type hints.

1 files changed, 39 insertions, 4 deletions

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,
+        })
     }
 }