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.

3 files changed, 206 insertions, 8 deletions

diff --git a/crates/ra_ide_api/src/lib.rs b/crates/ra_ide_api/src/lib.rs
index 3e7cfbb54..b8a4adbce 100644
--- a/crates/ra_ide_api/src/lib.rs
+++ b/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
diff --git a/crates/ra_ide_api/src/syntax_tree.rs b/crates/ra_ide_api/src/syntax_tree.rs
new file mode 100644
index 000000000..cdee63d59
--- /dev/null
+++ b/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

+}

diff --git a/crates/ra_ide_api/tests/test/main.rs b/crates/ra_ide_api/tests/test/main.rs
index b0c80e255..0f0766f62 100644
--- a/crates/ra_ide_api/tests/test/main.rs
+++ b/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()
+    );
+}