Implement syntax tree support for syntax inside string

This allows us to select a string or portions of it and try parsing it as rust
syntax. This is mostly helpful when developing tests where the test
itself contains some rust syntax as a string.

crates/ra_ide_api/src/lib.rs

@@ -32,13 +32,14 @@ mod references;
 mod impls;
 mod assists;
 mod diagnostics;
+mod syntax_tree;
 
 #[cfg(test)]
 mod marks;
 
 use std::sync::Arc;
 
-use ra_syntax::{SourceFile, TreeArc, TextRange, TextUnit, AstNode, algo};
+use ra_syntax::{SourceFile, TreeArc, TextRange, TextUnit};
 use ra_text_edit::TextEdit;
 use ra_db::{
     SourceDatabase, CheckCanceled,
@@ -246,13 +247,7 @@ impl Analysis {
     /// Returns a syntax tree represented as `String`, for debug purposes.
     // FIXME: use a better name here.
     pub fn syntax_tree(&self, file_id: FileId, text_range: Option<TextRange>) -> String {
-        if let Some(text_range) = text_range {
-            let file = self.db.parse(file_id);
-            let node = algo::find_covering_node(file.syntax(), text_range);
-            node.debug_dump()
-        } else {
-            self.db.parse(file_id).syntax().debug_dump()
-        }
+        syntax_tree::syntax_tree(&self.db, file_id, text_range)
     }
 
     /// Returns an edit to remove all newlines in the range, cleaning up minor

crates/ra_ide_api/src/syntax_tree.rs

@@ -0,0 +1,85 @@
+use ra_db::SourceDatabase;
+use crate::db::RootDatabase;
+use ra_syntax::{
+    SourceFile, SyntaxNode, TextRange, AstNode,
+    algo::{self, visit::{visitor, Visitor}}, ast::{self, AstToken}
+};
+
+pub use ra_db::FileId;
+
+pub(crate) fn syntax_tree(
+    db: &RootDatabase,
+    file_id: FileId,
+    text_range: Option<TextRange>,
+) -> String {
+    if let Some(text_range) = text_range {
+        let file = db.parse(file_id);
+        let node = algo::find_covering_node(file.syntax(), text_range);
+
+        if let Some(tree) = syntax_tree_for_string(node, text_range) {
+            return tree;
+        }
+
+        node.debug_dump()
+    } else {
+        db.parse(file_id).syntax().debug_dump()
+    }
+}
+
+/// Attempts parsing the selected contents of a string literal
+/// as rust syntax and returns its syntax tree
+fn syntax_tree_for_string(node: &SyntaxNode, text_range: TextRange) -> Option<String> {
+    // When the range is inside a string
+    // we'll attempt parsing it as rust syntax
+    // to provide the syntax tree of the contents of the string
+    visitor()
+        .visit(|node: &ast::String| syntax_tree_for_token(node, text_range))
+        .visit(|node: &ast::RawString| syntax_tree_for_token(node, text_range))
+        .accept(node)?
+}
+
+fn syntax_tree_for_token<T: AstToken>(node: &T, text_range: TextRange) -> Option<String> {
+    // Range of the full node
+    let node_range = node.syntax().range();
+    let text = node.text().to_string();
+
+    // We start at some point inside the node
+    // Either we have selected the whole string
+    // or our selection is inside it
+    let start = text_range.start() - node_range.start();
+
+    // how many characters we have selected
+    let len = text_range.len().to_usize();
+
+    let node_len = node_range.len().to_usize();
+
+    let start = start.to_usize();
+
+    // We want to cap our length
+    let len = len.min(node_len);
+
+    // Ensure our slice is inside the actual string
+    let end = if start + len < text.len() { start + len } else { text.len() - start };
+
+    let text = &text[start..end];
+
+    // Remove possible extra string quotes from the start
+    // and the end of the string
+    let text = text
+        .trim_start_matches('r')
+        .trim_start_matches('#')
+        .trim_start_matches('"')
+        .trim_end_matches('#')
+        .trim_end_matches('"')
+        .trim();
+
+    let parsed = SourceFile::parse(&text);
+
+    // If the "file" parsed without errors,
+    // return its syntax
+    if parsed.errors().is_empty() {
+        return Some(parsed.syntax().debug_dump());
+    }
+
+    None
+}

crates/ra_ide_api/tests/test/main.rs

@@ -272,3 +272,121 @@ EXPR_STMT@[16; 58)
         .trim()
     );
 }
+
+#[test]
+fn test_syntax_tree_inside_string() {
+    let (analysis, range) = single_file_with_range(
+        r#"fn test() {
+    assert!("
+<|>fn foo() {
+}<|>
+fn bar() {
+}
+    ", "");
+}"#
+        .trim(),
+    );
+    let syn = analysis.syntax_tree(range.file_id, Some(range.range));
+    assert_eq!(
+        syn.trim(),
+        r#"
+SOURCE_FILE@[0; 12)
+  FN_DEF@[0; 12)
+    FN_KW@[0; 2)
+    WHITESPACE@[2; 3)
+    NAME@[3; 6)
+      IDENT@[3; 6) "foo"
+    PARAM_LIST@[6; 8)
+      L_PAREN@[6; 7)
+      R_PAREN@[7; 8)
+    WHITESPACE@[8; 9)
+    BLOCK@[9; 12)
+      L_CURLY@[9; 10)
+      WHITESPACE@[10; 11)
+      R_CURLY@[11; 12)
+"#
+        .trim()
+    );
+
+    // With a raw string
+    let (analysis, range) = single_file_with_range(
+        r###"fn test() {
+    assert!(r#"
+<|>fn foo() {
+}<|>
+fn bar() {
+}
+    "#, "");
+}"###
+            .trim(),
+    );
+    let syn = analysis.syntax_tree(range.file_id, Some(range.range));
+    assert_eq!(
+        syn.trim(),
+        r#"
+SOURCE_FILE@[0; 12)
+  FN_DEF@[0; 12)
+    FN_KW@[0; 2)
+    WHITESPACE@[2; 3)
+    NAME@[3; 6)
+      IDENT@[3; 6) "foo"
+    PARAM_LIST@[6; 8)
+      L_PAREN@[6; 7)
+      R_PAREN@[7; 8)
+    WHITESPACE@[8; 9)
+    BLOCK@[9; 12)
+      L_CURLY@[9; 10)
+      WHITESPACE@[10; 11)
+      R_CURLY@[11; 12)
+"#
+        .trim()
+    );
+
+    // With a raw string
+    let (analysis, range) = single_file_with_range(
+        r###"fn test() {
+    assert!(r<|>#"
+fn foo() {
+}
+fn bar() {
+}"<|>#, "");
+}"###
+            .trim(),
+    );
+    let syn = analysis.syntax_tree(range.file_id, Some(range.range));
+    assert_eq!(
+        syn.trim(),
+        r#"
+SOURCE_FILE@[0; 25)
+  FN_DEF@[0; 12)
+    FN_KW@[0; 2)
+    WHITESPACE@[2; 3)
+    NAME@[3; 6)
+      IDENT@[3; 6) "foo"
+    PARAM_LIST@[6; 8)
+      L_PAREN@[6; 7)
+      R_PAREN@[7; 8)
+    WHITESPACE@[8; 9)
+    BLOCK@[9; 12)
+      L_CURLY@[9; 10)
+      WHITESPACE@[10; 11)
+      R_CURLY@[11; 12)
+  WHITESPACE@[12; 13)
+  FN_DEF@[13; 25)
+    FN_KW@[13; 15)
+    WHITESPACE@[15; 16)
+    NAME@[16; 19)
+      IDENT@[16; 19) "bar"
+    PARAM_LIST@[19; 21)
+      L_PAREN@[19; 20)
+      R_PAREN@[20; 21)
+    WHITESPACE@[21; 22)
+    BLOCK@[22; 25)
+      L_CURLY@[22; 23)
+      WHITESPACE@[23; 24)
+      R_CURLY@[24; 25)
+
+"#
+        .trim()
+    );
+}