1 files changed, 451 insertions, 0 deletions

diff --git a/crates/ra_analysis/src/call_info.rs b/crates/ra_analysis/src/call_info.rs
new file mode 100644
index 000000000..1dac95584
--- /dev/null
+++ b/crates/ra_analysis/src/call_info.rs
@@ -0,0 +1,451 @@
+use std::cmp::{max, min};
+
+use ra_db::{SyntaxDatabase, Cancelable};
+use ra_syntax::{
+    AstNode, SyntaxNode, TextUnit, TextRange,
+    SyntaxKind::FN_DEF,
+    ast::{self, ArgListOwner, DocCommentsOwner},
+};
+use ra_editor::find_node_at_offset;
+
+use crate::{FilePosition, CallInfo, db::RootDatabase};
+
+/// Computes parameter information for the given call expression.
+pub(crate) fn call_info(db: &RootDatabase, position: FilePosition) -> Cancelable<Option<CallInfo>> {
+    let file = db.source_file(position.file_id);
+    let syntax = file.syntax();
+
+    // Find the calling expression and it's NameRef
+    let calling_node = ctry!(FnCallNode::with_node(syntax, position.offset));
+    let name_ref = ctry!(calling_node.name_ref());
+
+    // Resolve the function's NameRef (NOTE: this isn't entirely accurate).
+    let file_symbols = db.index_resolve(name_ref)?;
+    let symbol = ctry!(file_symbols.into_iter().find(|it| it.ptr.kind() == FN_DEF));
+    let fn_file = db.source_file(symbol.file_id);
+    let fn_def = symbol.ptr.resolve(&fn_file);
+    let fn_def = ast::FnDef::cast(&fn_def).unwrap();
+    let mut call_info = ctry!(CallInfo::new(fn_def));
+    // If we have a calling expression let's find which argument we are on
+    let num_params = call_info.parameters.len();
+    let has_self = fn_def.param_list().and_then(|l| l.self_param()).is_some();
+
+    if num_params == 1 {
+        if !has_self {
+            call_info.active_parameter = Some(0);
+        }
+    } else if num_params > 1 {
+        // Count how many parameters into the call we are.
+        // TODO: This is best effort for now and should be fixed at some point.
+        // It may be better to see where we are in the arg_list and then check
+        // where offset is in that list (or beyond).
+        // Revisit this after we get documentation comments in.
+        if let Some(ref arg_list) = calling_node.arg_list() {
+            let start = arg_list.syntax().range().start();
+
+            let range_search = TextRange::from_to(start, position.offset);
+            let mut commas: usize = arg_list
+                .syntax()
+                .text()
+                .slice(range_search)
+                .to_string()
+                .matches(',')
+                .count();
+
+            // If we have a method call eat the first param since it's just self.
+            if has_self {
+                commas += 1;
+            }
+
+            call_info.active_parameter = Some(commas);
+        }
+    }
+
+    Ok(Some(call_info))
+}
+
+enum FnCallNode<'a> {
+    CallExpr(&'a ast::CallExpr),
+    MethodCallExpr(&'a ast::MethodCallExpr),
+}
+
+impl<'a> FnCallNode<'a> {
+    pub fn with_node(syntax: &'a SyntaxNode, offset: TextUnit) -> Option<FnCallNode<'a>> {
+        if let Some(expr) = find_node_at_offset::<ast::CallExpr>(syntax, offset) {
+            return Some(FnCallNode::CallExpr(expr));
+        }
+        if let Some(expr) = find_node_at_offset::<ast::MethodCallExpr>(syntax, offset) {
+            return Some(FnCallNode::MethodCallExpr(expr));
+        }
+        None
+    }
+
+    pub fn name_ref(&self) -> Option<&'a ast::NameRef> {
+        match *self {
+            FnCallNode::CallExpr(call_expr) => Some(match call_expr.expr()?.kind() {
+                ast::ExprKind::PathExpr(path_expr) => path_expr.path()?.segment()?.name_ref()?,
+                _ => return None,
+            }),
+
+            FnCallNode::MethodCallExpr(call_expr) => call_expr
+                .syntax()
+                .children()
+                .filter_map(ast::NameRef::cast)
+                .nth(0),
+        }
+    }
+
+    pub fn arg_list(&self) -> Option<&'a ast::ArgList> {
+        match *self {
+            FnCallNode::CallExpr(expr) => expr.arg_list(),
+            FnCallNode::MethodCallExpr(expr) => expr.arg_list(),
+        }
+    }
+}
+
+impl CallInfo {
+    fn new(node: &ast::FnDef) -> Option<Self> {
+        let mut doc = None;
+
+        // Strip the body out for the label.
+        let mut label: String = if let Some(body) = node.body() {
+            let body_range = body.syntax().range();
+            let label: String = node
+                .syntax()
+                .children()
+                .filter(|child| !child.range().is_subrange(&body_range))
+                .map(|node| node.text().to_string())
+                .collect();
+            label
+        } else {
+            node.syntax().text().to_string()
+        };
+
+        if let Some((comment_range, docs)) = extract_doc_comments(node) {
+            let comment_range = comment_range
+                .checked_sub(node.syntax().range().start())
+                .unwrap();
+            let start = comment_range.start().to_usize();
+            let end = comment_range.end().to_usize();
+
+            // Remove the comment from the label
+            label.replace_range(start..end, "");
+
+            // Massage markdown
+            let mut processed_lines = Vec::new();
+            let mut in_code_block = false;
+            for line in docs.lines() {
+                if line.starts_with("```") {
+                    in_code_block = !in_code_block;
+                }
+
+                let line = if in_code_block && line.starts_with("```") && !line.contains("rust") {
+                    "```rust".into()
+                } else {
+                    line.to_string()
+                };
+
+                processed_lines.push(line);
+            }
+
+            if !processed_lines.is_empty() {
+                doc = Some(processed_lines.join("\n"));
+            }
+        }
+
+        Some(CallInfo {
+            parameters: param_list(node),
+            label: label.trim().to_owned(),
+            doc,
+            active_parameter: None,
+        })
+    }
+}
+
+fn extract_doc_comments(node: &ast::FnDef) -> Option<(TextRange, String)> {
+    if node.doc_comments().count() == 0 {
+        return None;
+    }
+
+    let comment_text = node.doc_comment_text();
+
+    let (begin, end) = node
+        .doc_comments()
+        .map(|comment| comment.syntax().range())
+        .map(|range| (range.start().to_usize(), range.end().to_usize()))
+        .fold((std::usize::MAX, std::usize::MIN), |acc, range| {
+            (min(acc.0, range.0), max(acc.1, range.1))
+        });
+
+    let range = TextRange::from_to(TextUnit::from_usize(begin), TextUnit::from_usize(end));
+
+    Some((range, comment_text))
+}
+
+fn param_list(node: &ast::FnDef) -> Vec<String> {
+    let mut res = vec![];
+    if let Some(param_list) = node.param_list() {
+        if let Some(self_param) = param_list.self_param() {
+            res.push(self_param.syntax().text().to_string())
+        }
+
+        // Maybe use param.pat here? See if we can just extract the name?
+        //res.extend(param_list.params().map(|p| p.syntax().text().to_string()));
+        res.extend(
+            param_list
+                .params()
+                .filter_map(|p| p.pat())
+                .map(|pat| pat.syntax().text().to_string()),
+        );
+    }
+    res
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::mock_analysis::single_file_with_position;
+
+    fn call_info(text: &str) -> CallInfo {
+        let (analysis, position) = single_file_with_position(text);
+        analysis.call_info(position).unwrap().unwrap()
+    }
+
+    #[test]
+    fn test_fn_signature_two_args_first() {
+        let info = call_info(
+            r#"fn foo(x: u32, y: u32) -> u32 {x + y}
+fn bar() { foo(<|>3, ); }"#,
+        );
+
+        assert_eq!(info.parameters, vec!("x".to_string(), "y".to_string()));
+        assert_eq!(info.active_parameter, Some(0));
+    }
+
+    #[test]
+    fn test_fn_signature_two_args_second() {
+        let info = call_info(
+            r#"fn foo(x: u32, y: u32) -> u32 {x + y}
+fn bar() { foo(3, <|>); }"#,
+        );
+
+        assert_eq!(info.parameters, vec!("x".to_string(), "y".to_string()));
+        assert_eq!(info.active_parameter, Some(1));
+    }
+
+    #[test]
+    fn test_fn_signature_for_impl() {
+        let info = call_info(
+            r#"struct F; impl F { pub fn new() { F{}} }
+fn bar() {let _ : F = F::new(<|>);}"#,
+        );
+
+        assert_eq!(info.parameters, Vec::<String>::new());
+        assert_eq!(info.active_parameter, None);
+    }
+
+    #[test]
+    fn test_fn_signature_for_method_self() {
+        let info = call_info(
+            r#"struct F;
+impl F {
+    pub fn new() -> F{
+        F{}
+    }
+
+    pub fn do_it(&self) {}
+}
+
+fn bar() {
+    let f : F = F::new();
+    f.do_it(<|>);
+}"#,
+        );
+
+        assert_eq!(info.parameters, vec!["&self".to_string()]);
+        assert_eq!(info.active_parameter, None);
+    }
+
+    #[test]
+    fn test_fn_signature_for_method_with_arg() {
+        let info = call_info(
+            r#"struct F;
+impl F {
+    pub fn new() -> F{
+        F{}
+    }
+
+    pub fn do_it(&self, x: i32) {}
+}
+
+fn bar() {
+    let f : F = F::new();
+    f.do_it(<|>);
+}"#,
+        );
+
+        assert_eq!(info.parameters, vec!["&self".to_string(), "x".to_string()]);
+        assert_eq!(info.active_parameter, Some(1));
+    }
+
+    #[test]
+    fn test_fn_signature_with_docs_simple() {
+        let info = call_info(
+            r#"
+/// test
+// non-doc-comment
+fn foo(j: u32) -> u32 {
+    j
+}
+
+fn bar() {
+    let _ = foo(<|>);
+}
+"#,
+        );
+
+        assert_eq!(info.parameters, vec!["j".to_string()]);
+        assert_eq!(info.active_parameter, Some(0));
+        assert_eq!(info.label, "fn foo(j: u32) -> u32".to_string());
+        assert_eq!(info.doc, Some("test".into()));
+    }
+
+    #[test]
+    fn test_fn_signature_with_docs() {
+        let info = call_info(
+            r#"
+/// Adds one to the number given.
+///
+/// # Examples
+///
+/// ```
+/// let five = 5;
+///
+/// assert_eq!(6, my_crate::add_one(5));
+/// ```
+pub fn add_one(x: i32) -> i32 {
+    x + 1
+}
+
+pub fn do() {
+    add_one(<|>
+}"#,
+        );
+
+        assert_eq!(info.parameters, vec!["x".to_string()]);
+        assert_eq!(info.active_parameter, Some(0));
+        assert_eq!(info.label, "pub fn add_one(x: i32) -> i32".to_string());
+        assert_eq!(
+            info.doc,
+            Some(
+                r#"Adds one to the number given.
+
+# Examples
+
+```rust
+let five = 5;
+
+assert_eq!(6, my_crate::add_one(5));
+```"#
+                    .into()
+            )
+        );
+    }
+
+    #[test]
+    fn test_fn_signature_with_docs_impl() {
+        let info = call_info(
+            r#"
+struct addr;
+impl addr {
+    /// Adds one to the number given.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let five = 5;
+    ///
+    /// assert_eq!(6, my_crate::add_one(5));
+    /// ```
+    pub fn add_one(x: i32) -> i32 {
+        x + 1
+    }
+}
+
+pub fn do_it() {
+    addr {};
+    addr::add_one(<|>);
+}"#,
+        );
+
+        assert_eq!(info.parameters, vec!["x".to_string()]);
+        assert_eq!(info.active_parameter, Some(0));
+        assert_eq!(info.label, "pub fn add_one(x: i32) -> i32".to_string());
+        assert_eq!(
+            info.doc,
+            Some(
+                r#"Adds one to the number given.
+
+# Examples
+
+```rust
+let five = 5;
+
+assert_eq!(6, my_crate::add_one(5));
+```"#
+                    .into()
+            )
+        );
+    }
+
+    #[test]
+    fn test_fn_signature_with_docs_from_actix() {
+        let info = call_info(
+            r#"
+pub trait WriteHandler<E>
+where
+    Self: Actor,
+    Self::Context: ActorContext,
+{
+    /// Method is called when writer emits error.
+    ///
+    /// If this method returns `ErrorAction::Continue` writer processing
+    /// continues otherwise stream processing stops.
+    fn error(&mut self, err: E, ctx: &mut Self::Context) -> Running {
+        Running::Stop
+    }
+
+    /// Method is called when writer finishes.
+    ///
+    /// By default this method stops actor's `Context`.
+    fn finished(&mut self, ctx: &mut Self::Context) {
+        ctx.stop()
+    }
+}
+
+pub fn foo() {
+    WriteHandler r;
+    r.finished(<|>);
+}
+
+"#,
+        );
+
+        assert_eq!(
+            info.parameters,
+            vec!["&mut self".to_string(), "ctx".to_string()]
+        );
+        assert_eq!(info.active_parameter, Some(1));
+        assert_eq!(
+            info.doc,
+            Some(
+                r#"Method is called when writer finishes.
+
+By default this method stops actor's `Context`."#
+                    .into()
+            )
+        );
+    }
+
+}