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//! YAML serialization helpers.
use crate::char_traits;
use crate::yaml::{Hash, Yaml};
use std::convert::From;
use std::error::Error;
use std::fmt::{self, Display};
/// An error when emitting YAML.
#[derive(Copy, Clone, Debug)]
pub enum EmitError {
/// A formatting error.
FmtError(fmt::Error),
}
impl Error for EmitError {
fn cause(&self) -> Option<&dyn Error> {
None
}
}
impl Display for EmitError {
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
match *self {
EmitError::FmtError(ref err) => Display::fmt(err, formatter),
}
}
}
impl From<fmt::Error> for EmitError {
fn from(f: fmt::Error) -> Self {
EmitError::FmtError(f)
}
}
/// The YAML serializer.
///
/// ```
/// # use yaml_rust2::{YamlLoader, YamlEmitter};
/// let input_string = "a: b\nc: d";
/// let yaml = YamlLoader::load_from_str(input_string).unwrap();
///
/// let mut output = String::new();
/// YamlEmitter::new(&mut output).dump(&yaml[0]).unwrap();
///
/// assert_eq!(output, r#"---
/// a: b
/// c: d"#);
/// ```
#[allow(clippy::module_name_repetitions)]
pub struct YamlEmitter<'a> {
writer: &'a mut dyn fmt::Write,
best_indent: usize,
compact: bool,
level: isize,
multiline_strings: bool,
}
/// A convenience alias for emitter functions that may fail without returning a value.
pub type EmitResult = Result<(), EmitError>;
// from serialize::json
fn escape_str(wr: &mut dyn fmt::Write, v: &str) -> Result<(), fmt::Error> {
wr.write_str("\"")?;
let mut start = 0;
for (i, byte) in v.bytes().enumerate() {
let escaped = match byte {
b'"' => "\\\"",
b'\\' => "\\\\",
b'\x00' => "\\u0000",
b'\x01' => "\\u0001",
b'\x02' => "\\u0002",
b'\x03' => "\\u0003",
b'\x04' => "\\u0004",
b'\x05' => "\\u0005",
b'\x06' => "\\u0006",
b'\x07' => "\\u0007",
b'\x08' => "\\b",
b'\t' => "\\t",
b'\n' => "\\n",
b'\x0b' => "\\u000b",
b'\x0c' => "\\f",
b'\r' => "\\r",
b'\x0e' => "\\u000e",
b'\x0f' => "\\u000f",
b'\x10' => "\\u0010",
b'\x11' => "\\u0011",
b'\x12' => "\\u0012",
b'\x13' => "\\u0013",
b'\x14' => "\\u0014",
b'\x15' => "\\u0015",
b'\x16' => "\\u0016",
b'\x17' => "\\u0017",
b'\x18' => "\\u0018",
b'\x19' => "\\u0019",
b'\x1a' => "\\u001a",
b'\x1b' => "\\u001b",
b'\x1c' => "\\u001c",
b'\x1d' => "\\u001d",
b'\x1e' => "\\u001e",
b'\x1f' => "\\u001f",
b'\x7f' => "\\u007f",
_ => continue,
};
if start < i {
wr.write_str(&v[start..i])?;
}
wr.write_str(escaped)?;
start = i + 1;
}
if start != v.len() {
wr.write_str(&v[start..])?;
}
wr.write_str("\"")?;
Ok(())
}
impl<'a> YamlEmitter<'a> {
/// Create a new emitter serializing into `writer`.
pub fn new(writer: &'a mut dyn fmt::Write) -> YamlEmitter {
YamlEmitter {
writer,
best_indent: 2,
compact: true,
level: -1,
multiline_strings: false,
}
}
/// Set 'compact inline notation' on or off, as described for block
/// [sequences](http://www.yaml.org/spec/1.2/spec.html#id2797382)
/// and
/// [mappings](http://www.yaml.org/spec/1.2/spec.html#id2798057).
///
/// In this form, blocks cannot have any properties (such as anchors
/// or tags), which should be OK, because this emitter doesn't
/// (currently) emit those anyways.
pub fn compact(&mut self, compact: bool) {
self.compact = compact;
}
/// Determine if this emitter is using 'compact inline notation'.
#[must_use]
pub fn is_compact(&self) -> bool {
self.compact
}
/// Render strings containing multiple lines in [literal style].
///
/// # Examples
///
/// ```rust
/// use yaml_rust2::{Yaml, YamlEmitter, YamlLoader};
///
/// let input = r#"{foo: "bar!\nbar!", baz: 42}"#;
/// let parsed = YamlLoader::load_from_str(input).unwrap();
/// eprintln!("{:?}", parsed);
///
/// let mut output = String::new();
/// let mut emitter = YamlEmitter::new(&mut output);
/// emitter.multiline_strings(true);
/// emitter.dump(&parsed[0]).unwrap();
/// assert_eq!(output.as_str(), "\
/// ---
/// foo: |
/// bar!
/// bar!
/// baz: 42");
/// ```
///
/// [literal style]: https://yaml.org/spec/1.2/spec.html#id2795688
pub fn multiline_strings(&mut self, multiline_strings: bool) {
self.multiline_strings = multiline_strings;
}
/// Determine if this emitter will emit multiline strings when appropriate.
#[must_use]
pub fn is_multiline_strings(&self) -> bool {
self.multiline_strings
}
/// Dump Yaml to an output stream.
/// # Errors
/// Returns `EmitError` when an error occurs.
pub fn dump(&mut self, doc: &Yaml) -> EmitResult {
// write DocumentStart
writeln!(self.writer, "---")?;
self.level = -1;
self.emit_node(doc)
}
fn write_indent(&mut self) -> EmitResult {
if self.level <= 0 {
return Ok(());
}
for _ in 0..self.level {
for _ in 0..self.best_indent {
write!(self.writer, " ")?;
}
}
Ok(())
}
fn emit_node(&mut self, node: &Yaml) -> EmitResult {
match *node {
Yaml::Array(ref v) => self.emit_array(v),
Yaml::Hash(ref h) => self.emit_hash(h),
Yaml::String(ref v) => {
if self.multiline_strings
&& v.contains('\n')
&& char_traits::is_valid_literal_block_scalar(v)
{
write!(self.writer, "|")?;
self.level += 1;
for line in v.lines() {
writeln!(self.writer)?;
self.write_indent()?;
// It's literal text, so don't escape special chars.
write!(self.writer, "{line}")?;
}
self.level -= 1;
} else if need_quotes(v) {
escape_str(self.writer, v)?;
} else {
write!(self.writer, "{v}")?;
}
Ok(())
}
Yaml::Boolean(v) => {
if v {
self.writer.write_str("true")?;
} else {
self.writer.write_str("false")?;
}
Ok(())
}
Yaml::Integer(v) => {
write!(self.writer, "{v}")?;
Ok(())
}
Yaml::Real(ref v) => {
write!(self.writer, "{v}")?;
Ok(())
}
Yaml::Null | Yaml::BadValue => {
write!(self.writer, "~")?;
Ok(())
}
// XXX(chenyh) Alias
Yaml::Alias(_) => Ok(()),
}
}
fn emit_array(&mut self, v: &[Yaml]) -> EmitResult {
if v.is_empty() {
write!(self.writer, "[]")?;
} else {
self.level += 1;
for (cnt, x) in v.iter().enumerate() {
if cnt > 0 {
writeln!(self.writer)?;
self.write_indent()?;
}
write!(self.writer, "-")?;
self.emit_val(true, x)?;
}
self.level -= 1;
}
Ok(())
}
fn emit_hash(&mut self, h: &Hash) -> EmitResult {
if h.is_empty() {
self.writer.write_str("{}")?;
} else {
self.level += 1;
for (cnt, (k, v)) in h.iter().enumerate() {
let complex_key = matches!(*k, Yaml::Hash(_) | Yaml::Array(_));
if cnt > 0 {
writeln!(self.writer)?;
self.write_indent()?;
}
if complex_key {
write!(self.writer, "?")?;
self.emit_val(true, k)?;
writeln!(self.writer)?;
self.write_indent()?;
write!(self.writer, ":")?;
self.emit_val(true, v)?;
} else {
self.emit_node(k)?;
write!(self.writer, ":")?;
self.emit_val(false, v)?;
}
}
self.level -= 1;
}
Ok(())
}
/// Emit a yaml as a hash or array value: i.e., which should appear
/// following a ":" or "-", either after a space, or on a new line.
/// If `inline` is true, then the preceding characters are distinct
/// and short enough to respect the compact flag.
fn emit_val(&mut self, inline: bool, val: &Yaml) -> EmitResult {
match *val {
Yaml::Array(ref v) => {
if (inline && self.compact) || v.is_empty() {
write!(self.writer, " ")?;
} else {
writeln!(self.writer)?;
self.level += 1;
self.write_indent()?;
self.level -= 1;
}
self.emit_array(v)
}
Yaml::Hash(ref h) => {
if (inline && self.compact) || h.is_empty() {
write!(self.writer, " ")?;
} else {
writeln!(self.writer)?;
self.level += 1;
self.write_indent()?;
self.level -= 1;
}
self.emit_hash(h)
}
_ => {
write!(self.writer, " ")?;
self.emit_node(val)
}
}
}
}
/// Check if the string requires quoting.
/// Strings starting with any of the following characters must be quoted.
/// :, &, *, ?, |, -, <, >, =, !, %, @
/// Strings containing any of the following characters must be quoted.
/// {, }, \[, t \], ,, #, `
///
/// If the string contains any of the following control characters, it must be escaped with double quotes:
/// \0, \x01, \x02, \x03, \x04, \x05, \x06, \a, \b, \t, \n, \v, \f, \r, \x0e, \x0f, \x10, \x11, \x12, \x13, \x14, \x15, \x16, \x17, \x18, \x19, \x1a, \e, \x1c, \x1d, \x1e, \x1f, \N, \_, \L, \P
///
/// Finally, there are other cases when the strings must be quoted, no matter if you're using single or double quotes:
/// * When the string is true or false (otherwise, it would be treated as a boolean value);
/// * When the string is null or ~ (otherwise, it would be considered as a null value);
/// * When the string looks like a number, such as integers (e.g. 2, 14, etc.), floats (e.g. 2.6, 14.9) and exponential numbers (e.g. 12e7, etc.) (otherwise, it would be treated as a numeric value);
/// * When the string looks like a date (e.g. 2014-12-31) (otherwise it would be automatically converted into a Unix timestamp).
#[allow(clippy::doc_markdown)]
fn need_quotes(string: &str) -> bool {
fn need_quotes_spaces(string: &str) -> bool {
string.starts_with(' ') || string.ends_with(' ')
}
string.is_empty()
|| need_quotes_spaces(string)
|| string.starts_with(|character: char| {
matches!(
character,
'&' | '*' | '?' | '|' | '-' | '<' | '>' | '=' | '!' | '%' | '@'
)
})
|| string.contains(|character: char| {
matches!(character, ':'
| '{'
| '}'
| '['
| ']'
| ','
| '#'
| '`'
| '\"'
| '\''
| '\\'
| '\0'..='\x06'
| '\t'
| '\n'
| '\r'
| '\x0e'..='\x1a'
| '\x1c'..='\x1f')
})
|| [
// http://yaml.org/type/bool.html
// Note: 'y', 'Y', 'n', 'N', is not quoted deliberately, as in libyaml. PyYAML also parse
// them as string, not booleans, although it is violating the YAML 1.1 specification.
// See https://github.com/dtolnay/serde-yaml/pull/83#discussion_r152628088.
"yes", "Yes", "YES", "no", "No", "NO", "True", "TRUE", "true", "False", "FALSE",
"false", "on", "On", "ON", "off", "Off", "OFF",
// http://yaml.org/type/null.html
"null", "Null", "NULL", "~",
]
.contains(&string)
|| string.starts_with('.')
|| string.starts_with("0x")
|| string.parse::<i64>().is_ok()
|| string.parse::<f64>().is_ok()
}
#[cfg(test)]
mod test {
use super::YamlEmitter;
use crate::YamlLoader;
#[test]
fn test_multiline_string() {
let input = r#"{foo: "bar!\nbar!", baz: 42}"#;
let parsed = YamlLoader::load_from_str(input).unwrap();
let mut output = String::new();
let mut emitter = YamlEmitter::new(&mut output);
emitter.multiline_strings(true);
emitter.dump(&parsed[0]).unwrap();
}
}