Add hover

crates/lang_srv/src/convert.rs

@@ -1,17 +1,70 @@
-use roc_region::all::{LineColumnRegion, LineInfo, Region};
+use roc_region::all::{LineColumn, LineColumnRegion, LineInfo, Region};
 use tower_lsp::lsp_types::{Position, Range};
 
-fn range_of_region(line_info: &LineInfo, region: Region) -> Range {
-    let LineColumnRegion { start, end } = line_info.convert_region(region);
-    Range {
-        start: Position {
-            line: start.line,
-            character: start.column,
-        },
-        end: Position {
-            line: end.line,
-            character: end.column,
-        },
+pub(crate) trait ToRange {
+    type Feed;
+
+    fn to_range(&self, feed: &Self::Feed) -> Range;
+}
+
+impl ToRange for Region {
+    type Feed = LineInfo;
+
+    fn to_range(&self, line_info: &LineInfo) -> Range {
+        let LineColumnRegion { start, end } = line_info.convert_region(*self);
+        Range {
+            start: Position {
+                line: start.line,
+                character: start.column,
+            },
+            end: Position {
+                line: end.line,
+                character: end.column,
+            },
+        }
+    }
+}
+
+pub(crate) trait ToRegion {
+    type Feed;
+
+    fn to_region(&self, feed: &Self::Feed) -> Region;
+}
+
+impl ToRegion for Range {
+    type Feed = LineInfo;
+
+    fn to_region(&self, line_info: &LineInfo) -> Region {
+        let lc_region = LineColumnRegion {
+            start: LineColumn {
+                line: self.start.line,
+                column: self.start.character,
+            },
+            end: LineColumn {
+                line: self.end.line,
+                column: self.end.line,
+            },
+        };
+
+        line_info.convert_line_column_region(lc_region)
+    }
+}
+
+pub(crate) trait ToRocPosition {
+    type Feed;
+
+    fn to_roc_position(&self, feed: &Self::Feed) -> roc_region::all::Position;
+}
+
+impl ToRocPosition for tower_lsp::lsp_types::Position {
+    type Feed = LineInfo;
+
+    fn to_roc_position(&self, line_info: &LineInfo) -> roc_region::all::Position {
+        let lc = LineColumn {
+            line: self.line,
+            column: self.character,
+        };
+        line_info.convert_line_column(lc)
     }
 }
 
@@ -25,7 +78,7 @@ pub(crate) mod diag {
     use roc_reporting::report::{RocDocAllocator, Severity};
     use tower_lsp::lsp_types::{Diagnostic, DiagnosticSeverity, Position, Range};
 
-    use super::range_of_region;
+    use super::ToRange;
 
     pub trait IntoLspSeverity {
         fn into_lsp_severity(self) -> DiagnosticSeverity;
@@ -114,7 +167,7 @@ pub(crate) mod diag {
         type Feed = ProblemFmt<'a>;
 
         fn into_lsp_diagnostic(self, fmt: &'a ProblemFmt<'a>) -> Option<Diagnostic> {
-            let range = range_of_region(fmt.line_info, self.region());
+            let range = self.region().to_range(fmt.line_info);
 
             let report = roc_reporting::report::can_problem(
                 &fmt.alloc,
@@ -146,7 +199,7 @@ pub(crate) mod diag {
         type Feed = ProblemFmt<'a>;
 
         fn into_lsp_diagnostic(self, fmt: &'a ProblemFmt<'a>) -> Option<Diagnostic> {
-            let range = range_of_region(fmt.line_info, self.region());
+            let range = self.region().to_range(fmt.line_info);
 
             let report = roc_reporting::report::type_problem(
                 &fmt.alloc,

crates/lang_srv/src/registry.rs

@@ -4,9 +4,12 @@ use bumpalo::Bump;
 use roc_load::{LoadedModule, LoadingProblem};
 use roc_region::all::LineInfo;
 use roc_reporting::report::RocDocAllocator;
-use tower_lsp::lsp_types::{Diagnostic, Url};
+use tower_lsp::lsp_types::{Diagnostic, Hover, HoverContents, MarkedString, Position, Url};
 
-use crate::convert::diag::{IntoLspDiagnostic, ProblemFmt};
+use crate::convert::{
+    diag::{IntoLspDiagnostic, ProblemFmt},
+    ToRange, ToRocPosition,
+};
 
 pub(crate) enum DocumentChange {
     Modified(Url, String),
@@ -21,6 +24,7 @@ struct Document {
     arena: Bump,
 
     // Incrementally updated module, diagnostis, etc.
+    line_info: Option<LineInfo>,
     module: Option<Result<LoadedModule, ()>>,
     diagnostics: Option<Vec<Diagnostic>>,
 }
@@ -32,6 +36,7 @@ impl Document {
             source,
             arena: Bump::new(),
 
+            line_info: None,
             module: None,
             diagnostics: None,
         }
@@ -43,6 +48,16 @@ impl Document {
         self.diagnostics = None;
     }
 
+    fn prime_line_info(&mut self) {
+        if self.line_info.is_none() {
+            self.line_info = Some(LineInfo::new(&self.source));
+        }
+    }
+
+    fn line_info(&self) -> &LineInfo {
+        &self.line_info.as_ref().unwrap()
+    }
+
     fn module(&mut self) -> Result<&mut LoadedModule, LoadingProblem<'_>> {
         if let Some(Ok(module)) = &mut self.module {
             // Safety: returning for time self is alive
@@ -84,8 +99,11 @@ impl Document {
 
         let diagnostics = match loaded {
             Ok(module) => {
+                let line_info = {
+                    self.prime_line_info();
+                    self.line_info()
+                };
                 let lines: Vec<_> = self.source.lines().collect();
-                let line_info = LineInfo::new(&self.source);
 
                 let alloc = RocDocAllocator::new(&lines, module.module_id, &module.interns);
 
@@ -129,6 +147,41 @@ impl Document {
         self.diagnostics = Some(diagnostics);
         self.diagnostics.as_ref().unwrap().clone()
     }
+
+    fn hover(&mut self, position: Position) -> Option<Hover> {
+        let line_info = {
+            self.prime_line_info();
+            self.line_info()
+        };
+
+        let position = position.to_roc_position(line_info);
+
+        let module = match self.module() {
+            Ok(module) => module,
+            Err(_) => return None,
+        };
+
+        let decls = module.declarations_by_id.get(&module.module_id).unwrap();
+        let (region, var) = roc_can::traverse::find_closest_type_at(position, decls)?;
+
+        let subs = module.solved.inner_mut();
+        let snapshot = subs.snapshot();
+        let type_str = roc_types::pretty_print::name_and_print_var(
+            var,
+            subs,
+            module.module_id,
+            &module.interns,
+            roc_types::pretty_print::DebugPrint::NOTHING,
+        );
+        subs.rollback_to(snapshot);
+
+        let range = region.to_range(self.line_info());
+
+        Some(Hover {
+            contents: HoverContents::Scalar(MarkedString::String(type_str)),
+            range: Some(range),
+        })
+    }
 }
 
 #[derive(Debug, Default)]
@@ -155,4 +208,8 @@ impl Registry {
     pub fn diagnostics(&mut self, document: &Url) -> Vec<Diagnostic> {
         self.documents.get_mut(document).unwrap().diagnostics()
     }
+
+    pub fn hover(&mut self, document: &Url, position: Position) -> Option<Hover> {
+        self.documents.get_mut(document).unwrap().hover(position)
+    }
 }

crates/lang_srv/src/server.rs

@@ -100,6 +100,20 @@ impl LanguageServer for RocLs {
     async fn shutdown(&self) -> Result<()> {
         Ok(())
     }
+
+    async fn hover(&self, params: HoverParams) -> Result<Option<Hover>> {
+        let HoverParams {
+            text_document_position_params:
+                TextDocumentPositionParams {
+                    text_document,
+                    position,
+                },
+            work_done_progress_params: _,
+        } = params;
+
+        let hover = self.registry().hover(&text_document.uri, position);
+        Ok(hover)
+    }
 }
 
 #[tokio::main]