rust/crates/ide/src/syntax_tree.rs

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#"
SOURCE_FILE@0..11
  FN@0..11
    FN_KW@0..2 "fn"
    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_EXPR@9..11
      L_CURLY@9..10 "{"
      R_CURLY@10..11 "}"
"#
            .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#"
SOURCE_FILE@0..60
  FN@0..60
    FN_KW@0..2 "fn"
    WHITESPACE@2..3 " "
    NAME@3..7
      IDENT@3..7 "test"
    PARAM_LIST@7..9
      L_PAREN@7..8 "("
      R_PAREN@8..9 ")"
    WHITESPACE@9..10 " "
    BLOCK_EXPR@10..60
      L_CURLY@10..11 "{"
      WHITESPACE@11..16 "\n    "
      EXPR_STMT@16..58
        MACRO_CALL@16..57
          PATH@16..22
            PATH_SEGMENT@16..22
              NAME_REF@16..22
                IDENT@16..22 "assert"
          BANG@22..23 "!"
          TOKEN_TREE@23..57
            L_PAREN@23..24 "("
            STRING@24..52 "\"\n    fn foo() {\n     ..."
            COMMA@52..53 ","
            WHITESPACE@53..54 " "
            STRING@54..56 "\"\""
            R_PAREN@56..57 ")"
        SEMICOLON@57..58 ";"
      WHITESPACE@58..59 "\n"
      R_CURLY@59..60 "}"
"#
            .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#"
FN@0..11
  FN_KW@0..2 "fn"
  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_EXPR@9..11
    L_CURLY@9..10 "{"
    R_CURLY@10..11 "}"
"#
            .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#"
EXPR_STMT@16..58
  MACRO_CALL@16..57
    PATH@16..22
      PATH_SEGMENT@16..22
        NAME_REF@16..22
          IDENT@16..22 "assert"
    BANG@22..23 "!"
    TOKEN_TREE@23..57
      L_PAREN@23..24 "("
      STRING@24..52 "\"\n    fn foo() {\n     ..."
      COMMA@52..53 ","
      WHITESPACE@53..54 " "
      STRING@54..56 "\"\""
      R_PAREN@56..57 ")"
  SEMICOLON@57..58 ";"
"#
            .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#"
SOURCE_FILE@0..12
  FN@0..12
    FN_KW@0..2 "fn"
    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_EXPR@9..12
      L_CURLY@9..10 "{"
      WHITESPACE@10..11 "\n"
      R_CURLY@11..12 "}"
"#
            .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#"
SOURCE_FILE@0..12
  FN@0..12
    FN_KW@0..2 "fn"
    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_EXPR@9..12
      L_CURLY@9..10 "{"
      WHITESPACE@10..11 "\n"
      R_CURLY@11..12 "}"
"#
            .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#"
SOURCE_FILE@0..25
  FN@0..12
    FN_KW@0..2 "fn"
    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_EXPR@9..12
      L_CURLY@9..10 "{"
      WHITESPACE@10..11 "\n"
      R_CURLY@11..12 "}"
  WHITESPACE@12..13 "\n"
  FN@13..25
    FN_KW@13..15 "fn"
    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_EXPR@22..25
      L_CURLY@22..23 "{"
      WHITESPACE@23..24 "\n"
      R_CURLY@24..25 "}"
"#
            .trim()
        );
    }
}