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|
//! This module implements `builtins.toXML`, which is a serialisation
//! of value information as well as internal tvix state that several
//! things in nixpkgs rely on.
use bstr::ByteSlice;
use std::{io::Write, rc::Rc};
use xml::writer::events::XmlEvent;
use xml::writer::EmitterConfig;
use xml::writer::EventWriter;
use crate::{ErrorKind, Value};
/// Recursively serialise a value to XML. The value *must* have been
/// deep-forced before being passed to this function.
pub fn value_to_xml<W: Write>(mut writer: W, value: &Value) -> Result<(), ErrorKind> {
let config = EmitterConfig {
perform_indent: true,
pad_self_closing: true,
// Nix uses single-quotes *only* in the document declaration,
// so we need to write it manually.
write_document_declaration: false,
..Default::default()
};
// Write a literal document declaration, using C++-Nix-style
// single quotes.
writeln!(writer, "<?xml version='1.0' encoding='utf-8'?>")?;
let mut writer = EventWriter::new_with_config(writer, config);
writer.write(XmlEvent::start_element("expr"))?;
value_variant_to_xml(&mut writer, value)?;
writer.write(XmlEvent::end_element())?;
// Unwrap the writer to add the final newline that C++ Nix adds.
writeln!(writer.into_inner())?;
Ok(())
}
fn write_typed_value<W: Write, V: ToString>(
w: &mut EventWriter<W>,
name: &str,
value: V,
) -> Result<(), ErrorKind> {
w.write(XmlEvent::start_element(name).attr("value", &value.to_string()))?;
w.write(XmlEvent::end_element())?;
Ok(())
}
fn value_variant_to_xml<W: Write>(w: &mut EventWriter<W>, value: &Value) -> Result<(), ErrorKind> {
match value {
Value::Thunk(t) => return value_variant_to_xml(w, &t.value()),
Value::Null => {
w.write(XmlEvent::start_element("null"))?;
w.write(XmlEvent::end_element())
}
Value::Bool(b) => return write_typed_value(w, "bool", b),
Value::Integer(i) => return write_typed_value(w, "int", i),
Value::Float(f) => return write_typed_value(w, "float", f),
Value::String(s) => return write_typed_value(w, "string", s.to_str()?),
Value::Path(p) => return write_typed_value(w, "path", p.to_string_lossy()),
Value::List(list) => {
w.write(XmlEvent::start_element("list"))?;
for elem in list.into_iter() {
value_variant_to_xml(w, elem)?;
}
w.write(XmlEvent::end_element())
}
Value::Attrs(attrs) => {
w.write(XmlEvent::start_element("attrs"))?;
for elem in attrs.iter() {
w.write(XmlEvent::start_element("attr").attr("name", &elem.0.to_str_lossy()))?;
value_variant_to_xml(w, elem.1)?;
w.write(XmlEvent::end_element())?;
}
w.write(XmlEvent::end_element())
}
Value::Closure(c) => {
w.write(XmlEvent::start_element("function"))?;
match &c.lambda.formals {
Some(formals) => {
let mut attrspat = XmlEvent::start_element("attrspat");
if formals.ellipsis {
attrspat = attrspat.attr("ellipsis", "1");
}
if let Some(ref name) = &formals.name {
attrspat = attrspat.attr("name", name.as_str());
}
w.write(attrspat)?;
for arg in formals.arguments.iter() {
w.write(
XmlEvent::start_element("attr").attr("name", &arg.0.to_str_lossy()),
)?;
w.write(XmlEvent::end_element())?;
}
w.write(XmlEvent::end_element())?;
}
None => {
// TODO(tazjin): tvix does not currently persist function
// argument names anywhere (whereas we do for formals, as
// that is required for other runtime behaviour). Because of
// this the implementation here is fake, always returning
// the same argument name.
//
// If we don't want to persist the data, we can re-parse the
// AST from the spans of the lambda's bytecode and figure it
// out that way, but it needs some investigating.
w.write(XmlEvent::start_element("varpat").attr("name", /* fake: */ "x"))?;
w.write(XmlEvent::end_element())?;
}
}
w.write(XmlEvent::end_element())
}
Value::Builtin(_) => {
w.write(XmlEvent::start_element("unevaluated"))?;
w.write(XmlEvent::end_element())
}
Value::AttrNotFound
| Value::Blueprint(_)
| Value::DeferredUpvalue(_)
| Value::UnresolvedPath(_)
| Value::Json(_)
| Value::FinaliseRequest(_) => {
return Err(ErrorKind::TvixBug {
msg: "internal value variant encountered in builtins.toXML",
metadata: Some(Rc::new(value.clone())),
})
}
Value::Catchable(_) => {
panic!("tvix bug: value_to_xml() called on a value which had not been deep-forced")
}
}?;
Ok(())
}
|
