/
comment.rs
110 lines (105 loc) · 3.39 KB
/
comment.rs
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use rnix::ast::{self, AstToken};
use rnix::{match_ast, SyntaxNode};
use rowan::ast::AstNode;
/// Implements functions for doc-comments according to rfc145.
pub trait DocComment {
fn doc_text(&self) -> Option<&str>;
}
impl DocComment for ast::Comment {
/// Function returns the contents of the doc-comment, if the [ast::Comment] is a
/// doc-comment, or None otherwise.
///
/// Note: [ast::Comment] holds both the single-line and multiline comment.
///
/// /**{content}*/
/// -> {content}
///
/// It is named `doc_text` to complement [ast::Comment::text].
fn doc_text(&self) -> Option<&str> {
let text = self.syntax().text();
// Check whether this is a doc-comment
if text.starts_with(r#"/**"#) && self.text().starts_with('*') {
self.text().strip_prefix('*')
} else {
None
}
}
}
/// Function retrieves a doc-comment from the [ast::Expr]
///
/// Returns an [Option<String>] of the first suitable doc-comment.
/// Returns [None] in case no suitable comment was found.
///
/// Doc-comments can appear in two places for any expression
///
/// ```nix
/// # (1) directly before the expression (anonymous)
/// /** Doc */
/// bar: bar;
///
/// # (2) when assigning a name.
/// {
/// /** Doc */
/// foo = bar: bar;
/// }
/// ```
///
/// If the doc-comment is not found in place (1) the search continues at place (2)
/// More precisely before the NODE_ATTRPATH_VALUE (ast)
/// If no doc-comment was found in place (1) or (2) this function returns None.
pub fn get_expr_docs(expr: &SyntaxNode) -> Option<String> {
if let Some(doc) = get_doc_comment(expr) {
// Found in place (1)
doc.doc_text().map(|v| v.to_owned())
} else if let Some(ref parent) = expr.parent() {
match_ast! {
match parent {
ast::AttrpathValue(_) => {
if let Some(doc_comment) = get_doc_comment(parent) {
doc_comment.doc_text().map(|v| v.to_owned())
}else{
None
}
},
_ => {
// Yet unhandled ast-nodes
None
}
}
}
// None
} else {
// There is no parent;
// No further places where a doc-comment could be.
None
}
}
/// Looks backwards from the given expression
/// Only whitespace or non-doc-comments are allowed in between an expression and the doc-comment.
/// Any other Node or Token stops the peek.
fn get_doc_comment(expr: &SyntaxNode) -> Option<ast::Comment> {
let mut prev = expr.prev_sibling_or_token();
loop {
match prev {
Some(rnix::NodeOrToken::Token(ref token)) => {
match_ast! { match token {
ast::Whitespace(_) => {
prev = token.prev_sibling_or_token();
},
ast::Comment(it) => {
if it.doc_text().is_some() {
break Some(it);
}else{
//Ignore non-doc comments.
prev = token.prev_sibling_or_token();
}
},
_ => {
break None;
}
}}
}
_ => break None,
};
}
}