Refactor formatting code out of ra_ida_api_light into ra_fmt.

crates/ra_fmt/src/lib.rs

@@ -0,0 +1,76 @@
+//! This crate provides some utilities for indenting rust code.
+//!
+use itertools::Itertools;
+use ra_syntax::{
+    AstNode,
+    SyntaxNode, SyntaxKind::*,
+    ast::{self, AstToken},
+    algo::generate,
+};
+
+pub fn reindent(text: &str, indent: &str) -> String {
+    let indent = format!("\n{}", indent);
+    text.lines().intersperse(&indent).collect()
+}
+
+/// If the node is on the beginning of the line, calculate indent.
+pub fn leading_indent(node: &SyntaxNode) -> Option<&str> {
+    for leaf in prev_leaves(node) {
+        if let Some(ws) = ast::Whitespace::cast(leaf) {
+            let ws_text = ws.text();
+            if let Some(pos) = ws_text.rfind('\n') {
+                return Some(&ws_text[pos + 1..]);
+            }
+        }
+        if leaf.leaf_text().unwrap().contains('\n') {
+            break;
+        }
+    }
+    None
+}
+
+fn prev_leaves(node: &SyntaxNode) -> impl Iterator<Item = &SyntaxNode> {
+    generate(prev_leaf(node), |&node| prev_leaf(node))
+}
+
+fn prev_leaf(node: &SyntaxNode) -> Option<&SyntaxNode> {
+    generate(node.ancestors().find_map(SyntaxNode::prev_sibling), |it| it.last_child()).last()
+}
+
+pub fn extract_trivial_expression(block: &ast::Block) -> Option<&ast::Expr> {
+    let expr = block.expr()?;
+    if expr.syntax().text().contains('\n') {
+        return None;
+    }
+    let non_trivial_children = block.syntax().children().filter(|it| match it.kind() {
+        WHITESPACE | L_CURLY | R_CURLY => false,
+        _ => it != &expr.syntax(),
+    });
+    if non_trivial_children.count() > 0 {
+        return None;
+    }
+    Some(expr)
+}
+
+pub fn compute_ws(left: &SyntaxNode, right: &SyntaxNode) -> &'static str {
+    match left.kind() {
+        L_PAREN | L_BRACK => return "",
+        L_CURLY => {
+            if let USE_TREE = right.kind() {
+                return "";
+            }
+        }
+        _ => (),
+    }
+    match right.kind() {
+        R_PAREN | R_BRACK => return "",
+        R_CURLY => {
+            if let USE_TREE = left.kind() {
+                return "";
+            }
+        }
+        DOT => return "",
+        _ => (),
+    }
+    " "
+}