lix/lix-doc/src/lib.rs

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// SPDX-FileCopyrightText: 2024 Jade Lovelace
//
// SPDX-License-Identifier: BSD-2-Clause OR MIT
//! library components of nix-doc
pub mod pprint;
use crate::pprint::pprint_args;
use rnix::types::{Lambda, TypedNode};
use rnix::SyntaxKind::*;
use rnix::{NodeOrToken, SyntaxNode, TextUnit, WalkEvent};
use std::ffi::{CStr, CString};
use std::fs;
use std::iter;
use std::os::raw::c_char;
use std::panic;
use std::ptr;
use std::{fmt::Display, str};
pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;
const DOC_INDENT: usize = 3;
struct SearchResult {
/// Name of the function
identifier: String,
/// Dedented documentation comments
doc: String,
/// Parameter block for the function
param_block: String,
}
fn find_pos(file: &str, line: usize, col: usize) -> usize {
let mut lines = 1;
let mut line_start = 0;
let mut it = file.chars().enumerate().peekable();
while let Some((count, ch)) = it.next() {
if ch == '\n' || ch == '\r' {
lines += 1;
let addend = if ch == '\r' && it.peek().map(|x| x.1) == Some('\n') {
it.next();
1
} else {
0
};
line_start = count + addend;
}
let col_diff = ((count as i32) - (line_start as i32)).abs() as usize;
if lines == line && col_diff == col {
return count;
}
}
unreachable!();
}
impl SearchResult {
fn format<P: Display>(&self, filename: P, line: usize) -> String {
format!(
"**Synopsis:** `{}` = {}\n\n{}\n\n# {}",
self.identifier.as_str(),
self.param_block,
indented(&self.doc, DOC_INDENT),
format!("{}:{}", filename, line).as_str(),
)
}
}
/// Emits a string `s` indented by `indent` spaces
fn indented(s: &str, indent: usize) -> String {
let indent_s = iter::repeat(' ').take(indent).collect::<String>();
s.split('\n')
.map(|line| indent_s.clone() + line)
.collect::<Vec<_>>()
.join("\n")
}
/// Cleans up a single line, erasing prefix single line comments but preserving indentation
fn cleanup_single_line<'a>(s: &'a str) -> &'a str {
let mut cmt_new_start = 0;
for (idx, ch) in s.char_indices() {
// if we find a character, save the byte position after it as our new string start
if ch == '#' || ch == '*' {
cmt_new_start = idx + 1;
break;
}
// if, instead, we are on a line with no starting comment characters, leave it alone as it
// will be handled by dedent later
if !ch.is_whitespace() {
break;
}
}
&s[cmt_new_start..]
}
/// Erases indents in comments. This is *almost* a normal dedent function, but it starts by looking
/// at the second line if it can.
fn dedent_comment(s: &str) -> String {
let mut whitespaces = 0;
let mut lines = s.lines();
let first = lines.next();
// scan for whitespace
for line in lines.chain(first) {
let line_whitespace = line.chars().take_while(|ch| ch.is_whitespace()).count();
if line_whitespace != line.len() {
// a non-whitespace line, perfect for taking whitespace off of
whitespaces = line_whitespace;
break;
}
}
// maybe the first considered line we found was indented further, so let's look for more lines
// that might have a shorter indent. In the case of one line, do nothing.
for line in s.lines().skip(1) {
let line_whitespace = line.chars().take_while(|ch| ch.is_whitespace()).count();
if line_whitespace != line.len() {
whitespaces = line_whitespace.min(whitespaces);
}
}
// delete up to `whitespaces` whitespace characters from each line and reconstitute the string
let mut out = String::new();
for line in s.lines() {
let content_begin = line.find(|ch: char| !ch.is_whitespace()).unwrap_or(0);
out.push_str(&line[content_begin.min(whitespaces)..]);
out.push('\n');
}
out.truncate(out.trim_end_matches('\n').len());
out
}
/// Deletes whitespace and leading comment characters
///
/// Oversight we are choosing to ignore: if you put # characters at the beginning of lines in a
/// multiline comment, they will be deleted.
fn cleanup_comments<S: AsRef<str>, I: DoubleEndedIterator<Item = S>>(comment: &mut I) -> String {
dedent_comment(
&comment
.rev()
.map(|small_comment| {
small_comment
.as_ref()
// space before multiline start
.trim_start()
// multiline starts
.trim_start_matches("/*")
// trailing so we can grab multiline end
.trim_end()
// multiline ends
.trim_end_matches("*/")
// extra space that was in the multiline
.trim()
.split('\n')
// erase single line comments and such
.map(cleanup_single_line)
.collect::<Vec<_>>()
.join("\n")
})
.collect::<Vec<_>>()
.join("\n"),
)
}
/// Get the docs for a specific function
pub fn get_function_docs(filename: &str, line: usize, col: usize) -> Option<String> {
let content = fs::read(filename).ok()?;
let decoded = str::from_utf8(&content).ok()?;
let pos = find_pos(&decoded, line, col);
let rowan_pos = TextUnit::from_usize(pos);
let tree = rnix::parse(decoded);
let mut lambda = None;
for node in tree.node().preorder() {
match node {
WalkEvent::Enter(n) => {
if n.text_range().start() >= rowan_pos && n.kind() == NODE_LAMBDA {
lambda = Lambda::cast(n);
break;
}
}
WalkEvent::Leave(_) => (),
}
}
let lambda = lambda?;
let res = visit_lambda("func".to_string(), &lambda);
Some(res.format(filename, line))
}
fn visit_lambda(name: String, lambda: &Lambda) -> SearchResult {
// grab the arguments
let param_block = pprint_args(&lambda);
// find the doc comment
let comment = find_comment(lambda.node().clone()).unwrap_or_else(|| "".to_string());
SearchResult {
identifier: name,
doc: comment,
param_block
}
}
fn find_comment(node: SyntaxNode) -> Option<String> {
let mut node = NodeOrToken::Node(node);
let mut comments = Vec::new();
loop {
loop {
if let Some(new) = node.prev_sibling_or_token() {
node = new;
break;
} else {
node = NodeOrToken::Node(node.parent()?);
}
}
match node.kind() {
TOKEN_COMMENT => match &node {
NodeOrToken::Token(token) => comments.push(token.text().clone()),
NodeOrToken::Node(_) => unreachable!(),
},
// This stuff is found as part of `the-fn = f: ...`
// here: ^^^^^^^^
NODE_KEY | TOKEN_ASSIGN => (),
t if t.is_trivia() => (),
_ => break,
}
}
let doc = cleanup_comments(&mut comments.iter().map(|c| c.as_str()));
Some(doc).filter(|it| !it.is_empty())
}
/// Get the docs for a function in the given file path at the given file position and return it as
/// a C string pointer
#[no_mangle]
pub extern "C" fn nd_get_function_docs(
filename: *const c_char,
line: usize,
col: usize,
) -> *const c_char {
let fname = unsafe { CStr::from_ptr(filename) };
fname
.to_str()
.ok()
.and_then(|f| {
panic::catch_unwind(|| get_function_docs(f, line, col))
.map_err(|e| {
eprintln!("panic!! {:#?}", e);
e
})
.ok()
})
.flatten()
.and_then(|s| CString::new(s).ok())
.map(|s| s.into_raw() as *const c_char)
.unwrap_or(ptr::null())
}
/// Call this to free a string from nd_get_function_docs
#[no_mangle]
pub extern "C" fn nd_free_string(s: *const c_char) {
unsafe {
// cast note: this cast is turning something that was cast to const
// back to mut
drop(CString::from_raw(s as *mut c_char));
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_bytepos() {
let fakefile = "abc\ndef\nghi";
assert_eq!(find_pos(fakefile, 2, 2), 5);
}
#[test]
fn test_bytepos_cursed() {
let fakefile = "abc\rdef\r\nghi";
assert_eq!(find_pos(fakefile, 2, 2), 5);
assert_eq!(find_pos(fakefile, 3, 2), 10);
}
#[test]
fn test_comment_stripping() {
let ex1 = ["/* blah blah blah\n foooo baaar\n blah */"];
assert_eq!(
cleanup_comments(&mut ex1.iter()),
"blah blah blah\n foooo baaar\nblah"
);
let ex2 = ["# a1", "# a2", "# aa"];
assert_eq!(cleanup_comments(&mut ex2.iter()), "aa\n a2\na1");
}
#[test]
fn test_dedent() {
let ex1 = "a\n b\n c\n d";
assert_eq!(dedent_comment(ex1), "a\nb\nc\n d");
let ex2 = "a\nb\nc";
assert_eq!(dedent_comment(ex2), ex2);
let ex3 = " a\n b\n\n c";
assert_eq!(dedent_comment(ex3), "a\nb\n\n c");
}
#[test]
fn test_single_line_comment_stripping() {
let ex1 = " * a";
let ex2 = " # a";
let ex3 = " a";
assert_eq!(cleanup_single_line(ex1), " a");
assert_eq!(cleanup_single_line(ex2), " a");
assert_eq!(cleanup_single_line(ex3), ex3);
}
}