1 files changed, 359 insertions, 0 deletions

diff --git a/crates/ide/src/syntax_tree.rs b/crates/ide/src/syntax_tree.rs
new file mode 100644
index 000000000..f80044959
--- /dev/null
+++ b/crates/ide/src/syntax_tree.rs
@@ -0,0 +1,359 @@
+use base_db::{FileId, SourceDatabase};
+use ide_db::RootDatabase;
+use syntax::{
+    algo, AstNode, NodeOrToken, SourceFile,
+    SyntaxKind::{RAW_STRING, STRING},
+    SyntaxToken, TextRange, TextSize,
+};
+
+// Feature: Show Syntax Tree
+//
+// Shows the parse tree of the current file. It exists mostly for debugging
+// rust-analyzer itself.
+//
+// |===
+// | Editor  | Action Name
+//
+// | VS Code | **Rust Analyzer: Show Syntax Tree**
+// |===
+pub(crate) fn syntax_tree(
+    db: &RootDatabase,
+    file_id: FileId,
+    text_range: Option<TextRange>,
+) -> String {
+    let parse = db.parse(file_id);
+    if let Some(text_range) = text_range {
+        let node = match algo::find_covering_element(parse.tree().syntax(), text_range) {
+            NodeOrToken::Node(node) => node,
+            NodeOrToken::Token(token) => {
+                if let Some(tree) = syntax_tree_for_string(&token, text_range) {
+                    return tree;
+                }
+                token.parent()
+            }
+        };
+
+        format!("{:#?}", node)
+    } else {
+        format!("{:#?}", parse.tree().syntax())
+    }
+}
+
+/// Attempts parsing the selected contents of a string literal
+/// as rust syntax and returns its syntax tree
+fn syntax_tree_for_string(token: &SyntaxToken, 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
+    match token.kind() {
+        STRING | RAW_STRING => syntax_tree_for_token(token, text_range),
+        _ => None,
+    }
+}
+
+fn syntax_tree_for_token(node: &SyntaxToken, text_range: TextRange) -> Option<String> {
+    // Range of the full node
+    let node_range = node.text_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();
+
+    let node_len = node_range.len();
+
+    let start = start;
+
+    // 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 < TextSize::of(&text) { start + len } else { TextSize::of(&text) - start };
+
+    let text = &text[TextRange::new(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()
+        // Remove custom markers
+        .replace("<|>", "");
+
+    let parsed = SourceFile::parse(&text);
+
+    // If the "file" parsed without errors,
+    // return its syntax
+    if parsed.errors().is_empty() {
+        return Some(format!("{:#?}", parsed.tree().syntax()));
+    }
+
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::assert_eq_text;
+
+    use crate::mock_analysis::{analysis_and_range, single_file};
+
+    #[test]
+    fn test_syntax_tree_without_range() {
+        // Basic syntax
+        let (analysis, file_id) = single_file(r#"fn foo() {}"#);
+        let syn = analysis.syntax_tree(file_id, None).unwrap();
+
+        assert_eq_text!(
+            syn.trim(),
+            r#"
+[email protected]
+  [email protected]
+    [email protected] "fn"
+    [email protected] " "
+    [email protected]
+      [email protected] "foo"
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
+    [email protected] " "
+    [email protected]
+      [email protected] "{"
+      [email protected] "}"
+"#
+            .trim()
+        );
+
+        let (analysis, file_id) = single_file(
+            r#"
+fn test() {
+    assert!("
+    fn foo() {
+    }
+    ", "");
+}"#
+            .trim(),
+        );
+        let syn = analysis.syntax_tree(file_id, None).unwrap();
+
+        assert_eq_text!(
+            syn.trim(),
+            r#"
+[email protected]
+  [email protected]
+    [email protected] "fn"
+    [email protected] " "
+    [email protected]
+      [email protected] "test"
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
+    [email protected] " "
+    [email protected]
+      [email protected] "{"
+      [email protected] "\n    "
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected]
+                [email protected] "assert"
+          [email protected] "!"
+          [email protected]
+            [email protected] "("
+            [email protected] "\"\n    fn foo() {\n     ..."
+            [email protected] ","
+            [email protected] " "
+            [email protected] "\"\""
+            [email protected] ")"
+        [email protected] ";"
+      [email protected] "\n"
+      [email protected] "}"
+"#
+            .trim()
+        );
+    }
+
+    #[test]
+    fn test_syntax_tree_with_range() {
+        let (analysis, range) = analysis_and_range(r#"<|>fn foo() {}<|>"#.trim());
+        let syn = analysis.syntax_tree(range.file_id, Some(range.range)).unwrap();
+
+        assert_eq_text!(
+            syn.trim(),
+            r#"
+[email protected]
+  [email protected] "fn"
+  [email protected] " "
+  [email protected]
+    [email protected] "foo"
+  [email protected]
+    [email protected] "("
+    [email protected] ")"
+  [email protected] " "
+  [email protected]
+    [email protected] "{"
+    [email protected] "}"
+"#
+            .trim()
+        );
+
+        let (analysis, range) = analysis_and_range(
+            r#"fn test() {
+    <|>assert!("
+    fn foo() {
+    }
+    ", "");<|>
+}"#
+            .trim(),
+        );
+        let syn = analysis.syntax_tree(range.file_id, Some(range.range)).unwrap();
+
+        assert_eq_text!(
+            syn.trim(),
+            r#"
+[email protected]
+  [email protected]
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected] "assert"
+    [email protected] "!"
+    [email protected]
+      [email protected] "("
+      [email protected] "\"\n    fn foo() {\n     ..."
+      [email protected] ","
+      [email protected] " "
+      [email protected] "\"\""
+      [email protected] ")"
+  [email protected] ";"
+"#
+            .trim()
+        );
+    }
+
+    #[test]
+    fn test_syntax_tree_inside_string() {
+        let (analysis, range) = analysis_and_range(
+            r#"fn test() {
+    assert!("
+<|>fn foo() {
+}<|>
+fn bar() {
+}
+    ", "");
+}"#
+            .trim(),
+        );
+        let syn = analysis.syntax_tree(range.file_id, Some(range.range)).unwrap();
+        assert_eq_text!(
+            syn.trim(),
+            r#"
+[email protected]
+  [email protected]
+    [email protected] "fn"
+    [email protected] " "
+    [email protected]
+      [email protected] "foo"
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
+    [email protected] " "
+    [email protected]
+      [email protected] "{"
+      [email protected] "\n"
+      [email protected] "}"
+"#
+            .trim()
+        );
+
+        // With a raw string
+        let (analysis, range) = analysis_and_range(
+            r###"fn test() {
+    assert!(r#"
+<|>fn foo() {
+}<|>
+fn bar() {
+}
+    "#, "");
+}"###
+                .trim(),
+        );
+        let syn = analysis.syntax_tree(range.file_id, Some(range.range)).unwrap();
+        assert_eq_text!(
+            syn.trim(),
+            r#"
+[email protected]
+  [email protected]
+    [email protected] "fn"
+    [email protected] " "
+    [email protected]
+      [email protected] "foo"
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
+    [email protected] " "
+    [email protected]
+      [email protected] "{"
+      [email protected] "\n"
+      [email protected] "}"
+"#
+            .trim()
+        );
+
+        // With a raw string
+        let (analysis, range) = analysis_and_range(
+            r###"fn test() {
+    assert!(r<|>#"
+fn foo() {
+}
+fn bar() {
+}"<|>#, "");
+}"###
+                .trim(),
+        );
+        let syn = analysis.syntax_tree(range.file_id, Some(range.range)).unwrap();
+        assert_eq_text!(
+            syn.trim(),
+            r#"
+[email protected]
+  [email protected]
+    [email protected] "fn"
+    [email protected] " "
+    [email protected]
+      [email protected] "foo"
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
+    [email protected] " "
+    [email protected]
+      [email protected] "{"
+      [email protected] "\n"
+      [email protected] "}"
+  [email protected] "\n"
+  [email protected]
+    [email protected] "fn"
+    [email protected] " "
+    [email protected]
+      [email protected] "bar"
+    [email protected]
+      [email protected] "("
+      [email protected] ")"
+    [email protected] " "
+    [email protected]
+      [email protected] "{"
+      [email protected] "\n"
+      [email protected] "}"
+"#
+            .trim()
+        );
+    }
+}