Make modules with tests runnable

Fixes #154

crates/ra_analysis/src/runnables.rs

@@ -0,0 +1,72 @@
+use ra_syntax::{
+    ast::{self, AstNode, NameOwner, ModuleItemOwner},
+    SourceFileNode, TextRange, SyntaxNodeRef,
+    TextUnit,
+};
+use crate::{
+    Analysis, FileId, FilePosition
+};
+
+#[derive(Debug)]
+pub struct Runnable {
+    pub range: TextRange,
+    pub kind: RunnableKind,
+}
+
+#[derive(Debug)]
+pub enum RunnableKind {
+    Test { name: String },
+    TestMod { path: String },
+    Bin,
+}
+
+pub fn runnables(
+    analysis: &Analysis,
+    file_node: &SourceFileNode,
+    file_id: FileId,
+) -> Vec<Runnable> {
+    file_node
+        .syntax()
+        .descendants()
+        .filter_map(|i| runnable(analysis, i, file_id))
+        .collect()
+}
+
+fn runnable<'a>(analysis: &Analysis, item: SyntaxNodeRef<'a>, file_id: FileId) -> Option<Runnable> {
+    if let Some(f) = ast::FnDef::cast(item) {
+        let name = f.name()?.text();
+        let kind = if name == "main" {
+            RunnableKind::Bin
+        } else if f.has_atom_attr("test") {
+            RunnableKind::Test {
+                name: name.to_string(),
+            }
+        } else {
+            return None;
+        };
+        Some(Runnable {
+            range: f.syntax().range(),
+            kind,
+        })
+    } else if let Some(m) = ast::Module::cast(item) {
+        if m.item_list()?
+            .items()
+            .map(ast::ModuleItem::syntax)
+            .filter_map(ast::FnDef::cast)
+            .any(|f| f.has_atom_attr("test"))
+        {
+            let postition = FilePosition {
+                file_id,
+                offset: m.syntax().range().start() + TextUnit::from_usize(1),
+            };
+            analysis.module_path(postition).ok()?.map(|path| Runnable {
+                range: m.syntax().range(),
+                kind: RunnableKind::TestMod { path },
+            })
+        } else {
+            None
+        }
+    } else {
+        None
+    }
+}