git.delta.rocks / jrsonnet / refs/commits / 7e2e5c591e04

1use std::collections::HashMap;2use std::ffi::{OsStr, OsString};3use std::fmt::{self, Display};4use std::path::PathBuf;5use std::process::Stdio;6use std::sync::{Arc, OnceLock};78use anyhow::{anyhow, bail, ensure, Context, Result};9use futures::StreamExt;10use itertools::Itertools;11use r2d2::{Pool, PooledConnection};12use serde::de::DeserializeOwned;13use serde::{Deserialize, Serialize};14use tokio::io::AsyncWriteExt;15use tokio::process::{ChildStderr, ChildStdin, ChildStdout, Command};16use tokio::select;17use tokio::sync::{mpsc, oneshot};18use tokio_util::codec::{FramedRead, LinesCodec};19use tracing::{debug, error, warn, Level};2021use crate::command::{ClonableHandler, Handler, NixHandler, NoopHandler};2223const REPL_DELIMITER: &str = "\"FLEET_MAGIC_REPL_DELIMITER\"";2425pub struct NixSessionInner {26	full_delimiter: String,27	nix_handler: ClonableHandler<NixHandler>,28	out: OutputHandler,29	stdin: ChildStdin,30	string_wrapping: (String, String),31	number_wrapping: (String, String),3233	next_id: u32,34	free_list: Vec<u32>,35}36const TRAIN_STRING: &str = "\"TRAIN_STRING\"";37const TRAIN_NUMBER: &str = "13141516";3839#[must_use]40struct ErrorCollector<'i, H> {41	collected: Vec<String>,42	inner: &'i mut H,43}44impl<'i, H> ErrorCollector<'i, H> {45	fn new(inner: &'i mut H) -> Self {46		Self {47			collected: vec![],48			inner,49		}50	}51}52impl<H> ErrorCollector<'_, H> {53	fn handle_line_inner(&mut self, msg: &str) -> bool {54		let Some(msg) = msg.strip_prefix("@nix ") else {55			return false;56		};57		#[derive(Deserialize)]58		struct ErrorAction {59			action: String,60			level: u32,61			msg: String,62		}63		let Ok(act) = serde_json::from_str::<ErrorAction>(msg) else {64			return false;65		};66		if act.action != "msg" || act.level != 0 {67			return false;68		}69		self.collected.push(act.msg);70		true71	}72	fn finish(self) -> Result<()> {73		// fn dedent(s: String) -> String {74		// 	s.split('\n').filter(|s| !s.trim().is_empty()).map(|v| v.)75		// }76		if !self.collected.is_empty() {77			bail!(78				"{}",79				self.collected80					.iter()81					.map(|v| {82						if let Some(f) = v.strip_prefix("\u{1b}[31;1merror:\u{1b}[0m ") {83							let v = unindent::unindent(f.trim_start());84							v.trim().to_owned()85						} else {86							v.to_owned()87						}88					})89					.join("\n")90			);91		}92		Ok(())93	}94	fn flush(self) {95		for line in self.collected {96			warn!("{line}");97		}98	}99}100impl<H: Handler> Handler for ErrorCollector<'_, H> {101	fn handle_line(&mut self, e: &str) {102		if self.handle_line_inner(e) {103			return;104		}105		self.inner.handle_line(e)106	}107}108109enum OutputLine {110	Out(String),111	Err(String),112}113struct OutputHandler {114	rx: mpsc::Receiver<OutputLine>,115	_cancel_handle: oneshot::Receiver<()>,116}117impl OutputHandler {118	fn new(out: ChildStdout, err: ChildStderr) -> Self {119		let mut out = FramedRead::new(out, LinesCodec::new());120		let mut err = FramedRead::new(err, LinesCodec::new());121		let (tx, rx) = mpsc::channel(20);122		let (mut cancelled, _cancel_handle) = oneshot::channel();123		tokio::spawn(async move {124			loop {125				select! {126					// We should receive errors earlier than synchronization127					biased;128					e = err.next() => {129						let Some(Ok(e)) = e else {130							if e.is_some() {131								error!("bad repl stderr: {e:?}");132							}133							continue;134						};135						let _ = tx.send(OutputLine::Err(e)).await;136					}137					o = out.next() => {138						let Some(Ok(o)) = o else {139							if o.is_some() {140								error!("bad repl stdout: {o:?}");141							}142							continue;143						};144						let _ = tx.send(OutputLine::Out(o)).await;145					}146					// Reader doesn't care about stdout, as this is cancelled.147					// Error still might be useful, to process leftover span closures?148					_ = cancelled.closed() => {149						break;150					}151				}152			}153		});154		Self { rx, _cancel_handle }155	}156	async fn next(&mut self) -> Option<OutputLine> {157		self.rx.recv().await158	}159}160161struct WarnHandler;162impl Handler for WarnHandler {163	fn handle_line(&mut self, e: &str) {164		warn!(target: "nix", "{e}")165	}166}167168impl NixSessionInner {169	async fn new(flake: &OsStr, extra_args: impl IntoIterator<Item = &OsStr>) -> Result<Self> {170		let mut cmd = Command::new("nix");171		cmd.arg("repl")172			.arg(flake)173			.arg("--log-format")174			.arg("internal-json");175		for arg in extra_args {176			cmd.arg(arg);177		}178		cmd.stdin(Stdio::piped());179		cmd.stdout(Stdio::piped());180		cmd.stderr(Stdio::piped());181		let cmd = cmd.spawn()?;182		let stdout = cmd.stdout.unwrap();183		let stderr = cmd.stderr.unwrap();184		let mut out = OutputHandler::new(stdout, stderr);185		let mut stdin = cmd.stdin.unwrap();186		// Standard repl hello doesn't work with internal-json logger187		stdin.write_all(REPL_DELIMITER.as_bytes()).await?;188		stdin.write_all(b"\n").await?;189		stdin.flush().await?;190		let nix_handler = NixHandler::default();191		let mut full_delimiter = None;192		let mut errors = vec![];193		while let Some(line) = out.next().await {194			let line = match line {195				OutputLine::Out(o) => o,196				OutputLine::Err(_e) => {197					// Handle startup errors, but skip repl hello?198					errors.push(_e);199					continue;200				}201			};202			if line.contains(REPL_DELIMITER) {203				debug!("discovered repl delimiter with added colors: {line}");204				full_delimiter = Some(line.to_owned());205				break;206			}207		}208		let Some(full_delimiter) = full_delimiter else {209			for e in errors {210				error!("{e}");211			}212			bail!("failed to discover delimiter");213		};214		let mut res = Self {215			full_delimiter,216			nix_handler: ClonableHandler::new(nix_handler),217			out,218			stdin,219			string_wrapping: Default::default(),220			number_wrapping: Default::default(),221222			next_id: 0,223			free_list: vec![],224		};225		res.train().await?;226		Ok(res)227	}228	async fn train(&mut self) -> Result<()> {229		{230			let full_string = self231				.execute_expression_raw(TRAIN_STRING, &mut NoopHandler)232				.await?;233			let string_offset = full_string.find(TRAIN_STRING).expect("contained");234			let string_prefix = &full_string[..string_offset];235			let string_suffix = &full_string[string_offset + TRAIN_STRING.len()..];236			self.string_wrapping = (string_prefix.to_owned(), string_suffix.to_owned());237		}238		{239			let full_number = self240				.execute_expression_raw(TRAIN_NUMBER, &mut NoopHandler)241				.await?;242			let number_offset = full_number.find(TRAIN_NUMBER).expect("contained");243			let number_prefix = &full_number[..number_offset];244			let number_suffix = &full_number[number_offset + TRAIN_NUMBER.len()..];245			self.number_wrapping = (number_prefix.to_owned(), number_suffix.to_owned());246		}247		Ok(())248	}249	async fn send_command(&mut self, cmd: impl AsRef<[u8]>) -> Result<()> {250		if tracing::enabled!(Level::DEBUG) {251			let cmd_str = String::from_utf8_lossy(cmd.as_ref());252			tracing::debug!("{cmd_str}");253		};254		self.stdin.write_all(cmd.as_ref()).await?;255		self.stdin.write_all(b"\n").await?;256		Ok(())257	}258	async fn read_until_delimiter(&mut self, err_handler: &mut dyn Handler) -> Result<String> {259		let mut out = String::new();260		while let Some(line) = self.out.next().await {261			let line = match line {262				OutputLine::Out(out) => out,263				OutputLine::Err(err) => {264					err_handler.handle_line(&err);265					continue;266				}267			};268			if line == self.full_delimiter {269				return Ok(out);270			}271			if !out.is_empty() {272				out.push('\n');273			}274			out.push_str(&line);275		}276		bail!("didn't reached delimiter");277	}278	async fn execute_expression_number(&mut self, expr: impl AsRef<[u8]>) -> Result<u64> {279		let num = self.number_wrapping.clone();280		let n = self.execute_expression_wrapping(expr, &num).await?;281		Ok(n.parse::<u64>()?)282	}283	async fn execute_expression_string(&mut self, expr: impl AsRef<[u8]>) -> Result<String> {284		let num = self.string_wrapping.clone();285		let n = self.execute_expression_wrapping(expr, &num).await?;286		let str: String = serde_json::from_str(&n)?;287		Ok(str)288	}289	async fn execute_expression_to_json<V: DeserializeOwned>(290		&mut self,291		expr: impl AsRef<[u8]>,292	) -> Result<V> {293		let mut fexpr = b"builtins.toJSON (".to_vec();294		fexpr.extend_from_slice(expr.as_ref());295		fexpr.push(b')');296		let v = self.execute_expression_string(fexpr).await?;297		Ok(serde_json::from_str(&v)?)298	}299	async fn execute_expression_wrapping(300		&mut self,301		expr: impl AsRef<[u8]>,302		wrapping: &(String, String),303	) -> Result<String> {304		let mut nix_handler = self.nix_handler.clone();305		let mut collected = ErrorCollector::new(&mut nix_handler);306		let res = self.execute_expression_raw(expr, &mut collected).await?;307		if res.is_empty() {308			collected.finish()?;309			bail!("expected expression, got nothing")310		} else {311			collected.flush()312		};313		let Some(res) = res.strip_prefix(&wrapping.0) else {314			bail!("invalid type")315		};316		let Some(res) = res.strip_suffix(&wrapping.1) else {317			bail!("invalid type")318		};319		Ok(res.to_owned())320	}321	async fn execute_expression_empty(&mut self, expr: impl AsRef<[u8]>) -> Result<()> {322		let mut nix_handler = self.nix_handler.clone();323		let mut collected = ErrorCollector::new(&mut nix_handler);324		let v = self.execute_expression_raw(expr, &mut collected).await?;325		collected.finish()?;326		ensure!(v.is_empty(), "unexpected expression result");327		Ok(())328	}329	async fn execute_expression_raw(330		&mut self,331		expr: impl AsRef<[u8]>,332		err_handler: &mut dyn Handler,333	) -> Result<String> {334		self.send_command(expr).await?;335		// It will be echoed336		self.send_command(REPL_DELIMITER).await?;337		self.read_until_delimiter(err_handler).await338	}339	async fn execute_assign(&mut self, expr: impl AsRef<str>) -> Result<u32> {340		let id = self.allocate_id();341		self.execute_expression_empty(format!("sess_field_{id} = {}", expr.as_ref()))342			.await?;343		Ok(id)344	}345346	/// Id should be immediately used347	fn allocate_id(&mut self) -> u32 {348		if let Some(free) = self.free_list.pop() {349			free350		} else {351			let v = self.next_id;352			self.next_id += 1;353			v354		}355	}356	// Nix has no way to deallocate variable, yet GC will correct everything not reachable.357	// async fn free_id(&mut self, id: u32) -> Result<()> {358	// 	self.execute_expression_empty(format!("sess_field_{id} = null"))359	// 		.await?;360	// 	self.free_list.push(id);361	// 	Ok(())362	// }363}364365#[derive(Clone)]366pub struct NixSession(Arc<tokio::sync::Mutex<PooledConnection<NixSessionPoolInner>>>);367368#[derive(Clone)]369pub struct NixExprBuilder {370	out: String,371	used_fields: Vec<Field>,372}373impl NixExprBuilder {374	pub fn object() -> Self {375		NixExprBuilder {376			out: "{ ".to_owned(),377			used_fields: Vec::new(),378		}379	}380	pub fn string(s: &str) -> Self {381		NixExprBuilder {382			out: nixlike::serialize(s)383				.expect("no problems with serializing_string")384				.trim_end()385				.to_owned(),386			used_fields: Vec::new(),387		}388	}389	pub fn serialized(v: impl Serialize) -> Self {390		let serialized = nixlike::serialize(v).expect("invalid value for apply");391		Self {392			out: serialized.trim_end().to_owned(),393			used_fields: Vec::new(),394		}395	}396	pub fn field(f: Field) -> Self {397		Self {398			out: format!("sess_field_{}", f.0.value.expect("no value")),399			used_fields: vec![f],400		}401	}402	pub fn end_obj(&mut self) {403		self.out.push('}');404	}405	pub fn obj_key(&mut self, name: Self, value: Self) {406		self.out.push_str(r#""${"#);407		self.extend(name);408		self.out.push_str(r#"}" = "#);409		self.extend(value);410		self.out.push_str("; ");411	}412413	pub fn extend(&mut self, e: Self) {414		self.out.push_str(&e.out);415		self.used_fields.extend(e.used_fields);416	}417418	pub fn session(&self) -> NixSession {419		let mut session = None;420		for ele in &self.used_fields {421			if session.is_none() {422				session = Some(ele.0.session.clone());423				continue;424			}425			let session = &session.as_ref().expect("checked").0;426			let ele_sess = &ele.0.session.0;427			assert!(428				Arc::ptr_eq(session, ele_sess),429				"can't mix fields from different session"430			);431		}432		session.expect("expr without fields used")433	}434	pub fn index_attr(&mut self, s: &str) {435		let escaped = nixlike::serialize(s).expect("string");436		self.out.push('.');437		self.out.push_str(escaped.trim_end());438	}439}440441#[macro_export]442macro_rules! nix_expr_inner {443	(Obj { $($ident:ident: $($val:tt)+),* $(,)? }) => {{444		use $crate::better_nix_eval::NixExprBuilder;445		let mut out = NixExprBuilder::object();446		$(447			out.obj_key(448				NixExprBuilder::string(stringify!($ident)),449				$crate::nix_expr_inner!($($val)+),450			);451		)*452		out.end_obj();453		out454	}};455	(@field($o:ident) . $var:ident $($tt:tt)*) => {{456		$o.index_attr(stringify!($var));457		nix_expr_inner!(@field($o) $($tt)*);458	}};459	(@field($o:ident) [{ $v:expr }] $($tt:tt)*) => {{460		$o.push(Index::attr(&$v));461		nix_expr_inner!(@o($o) $($tt)*);462	}};463	(@field($o:ident) [ $($var:tt)+ ] $($tt:tt)*) => {{464		$o.push(Index::Expr($crate::nix_expr_inner!($($var)+)));465		nix_expr_inner!(@o($o) $($tt)*);466	}};467	(@field($o:ident) ($($var:tt)*) $($tt:tt)*) => {468		$o.push(Index::ExprApply($crate::nix_expr_inner!($($var)+)));469		nix_expr_inner!(@o($o) $($tt)*);470	};471	(@field($o:ident)) => {};472	($field:ident $($tt:tt)*) => {{473		use $crate::{better_nix_eval::NixExprBuilder, nix_expr_inner};474		#[allow(unused_mut, reason = "might be used if indexed")]475		let mut out = NixExprBuilder::field($field);476		nix_expr_inner!(@field(out) $($tt)*);477		out478	}};479	($v:literal) => {{480		use $crate::better_nix_eval::NixExprBuilder;481		NixExprBuilder::string($v)482	}};483	({$v:expr}) => {{484		use $crate::better_nix_eval::NixExprBuilder;485		NixExprBuilder::serialized(&$v)486	}}487}488#[macro_export]489macro_rules! nix_expr {490	($($tt:tt)+) => {{491		use $crate::{better_nix_eval::{NixExprBuilder, Field}, nix_expr_inner};492		let expr = nix_expr_inner!($($tt)+);493		Field::new(expr.session(), expr.out)494	}};495}496497#[macro_export]498macro_rules! nix_go {499	(@o($o:ident) . $var:ident $($tt:tt)*) => {{500		$o.push(Index::attr(stringify!($var)));501		nix_go!(@o($o) $($tt)*);502	}};503	(@o($o:ident) [{ $v:expr }] $($tt:tt)*) => {{504		$o.push(Index::attr(&$v));505		nix_go!(@o($o) $($tt)*);506	}};507	(@o($o:ident) [ $($var:tt)+ ] $($tt:tt)*) => {{508		$o.push(Index::Expr($crate::nix_expr_inner!($($var)+)));509		nix_go!(@o($o) $($tt)*);510	}};511	(@o($o:ident) ($($var:tt)*) $($tt:tt)*) => {512		$o.push(Index::ExprApply($crate::nix_expr_inner!($($var)+)));513		nix_go!(@o($o) $($tt)*);514	};515	(@o($o:ident)) => {};516	($field:ident $($tt:tt)+) => {{517		use $crate::{nix_go, better_nix_eval::Index};518		let field = $field.clone();519		let mut out = vec![];520		nix_go!(@o(out) $($tt)*);521		field.select(out).await?522	}}523}524#[macro_export]525macro_rules! nix_go_json {526	($($tt:tt)*) => {{527		$crate::nix_go!($($tt)*).as_json().await?528	}};529}530531#[derive(Clone)]532pub enum Index {533	Var(String),534	String(String),535	Apply(String),536	Expr(NixExprBuilder),537	ExprApply(NixExprBuilder),538}539impl Index {540	pub fn var(v: impl AsRef<str>) -> Self {541		let v = v.as_ref();542		assert!(543			!(v.contains('.') | v.contains(' ')),544			"bad variable name: {v}"545		);546		Self::Var(v.to_owned())547	}548	pub fn attr(v: impl AsRef<str>) -> Self {549		Self::String(v.as_ref().to_owned())550	}551	pub fn apply(v: impl Serialize) -> Self {552		let serialized = nixlike::serialize(v).expect("invalid value for apply");553		Self::Apply(serialized.trim_end().to_owned())554	}555}556impl Display for Index {557	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {558		match self {559			Index::Var(v) => {560				write!(f, "{v}")561			}562			Index::String(k) => {563				let v = nixlike::format_identifier(k.as_str());564				write!(f, ".{v}")565			}566			Index::Apply(o) => {567				write!(f, "<apply>({o})")568			}569			Index::Expr(e) => {570				write!(f, "[{}]", e.out)571			}572			Index::ExprApply(e) => {573				write!(f, "<apply>({})", e.out)574			}575		}576	}577}578impl fmt::Debug for Index {579	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {580		write!(f, "{self}")581	}582}583struct PathDisplay<'i>(&'i [Index]);584impl Display for PathDisplay<'_> {585	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {586		for i in self.0 {587			write!(f, "{i}")?;588		}589		Ok(())590	}591}592struct FieldInner {593	full_path: Option<Vec<Index>>,594	session: NixSession,595	value: Option<u32>,596}597fn context(full_path: Option<&[Index]>, query: &str) -> String {598	if let Some(full_path) = &full_path {599		format!("full path: {}", PathDisplay(full_path))600	} else {601		format!("query: {query:?}")602	}603}604#[derive(Clone)]605pub struct Field(Arc<FieldInner>);606impl Field {607	fn root(session: NixSession) -> Self {608		Self(Arc::new(FieldInner {609			full_path: Some(vec![]),610			session,611			value: None,612		}))613	}614	async fn new(session: NixSession, query: &str) -> Result<Self> {615		let vid = session616			.0617			.lock()618			.await619			.execute_assign(query)620			.await621			.with_context(|| context(None, query))?;622		Ok(Self(Arc::new(FieldInner {623			full_path: None,624			session,625			value: Some(vid),626		})))627	}628	pub async fn field(session: NixSession, field: &str) -> Result<Self> {629		Self::root(session).select([Index::var(field)]).await630	}631	pub async fn get_json_deep<'a, V: DeserializeOwned>(632		&self,633		name: impl IntoIterator<Item = Index>,634	) -> Result<V> {635		let field = self.select(name).await?;636		field.as_json().await637	}638	pub async fn select<'a>(&self, name: impl IntoIterator<Item = Index>) -> Result<Self> {639		let mut used_fields = Vec::new();640		let mut name = name.into_iter();641642		let mut full_path = self.0.full_path.clone();643		let mut query = if let Some(id) = self.0.value {644			format!("sess_field_{id}")645		} else {646			let first = name.next();647			if let Some(Index::Var(i)) = first {648				if let Some(full_path) = &mut full_path {649					full_path.push(Index::Var(i.clone()));650				}651				i.clone()652			} else {653				panic!("first path item should be variable, got {first:?}")654			}655		};656		for v in name {657			if let Some(full_path) = &mut full_path {658				full_path.push(v.clone());659			}660			match v {661				Index::Var(_) => panic!("var item may only be first"),662				Index::String(s) => {663					let escaped = nixlike::serialize(s)?;664					query.push('.');665					query.push_str(escaped.trim());666				}667				Index::Apply(a) => {668					// In cases like `a {}.b` first `{}.b` will be evaluated, so `a {}` should be encased in `()`669					query = format!("({query} {a})");670				}671				Index::Expr(e) => {672					let index = Field::new(self.0.session.clone(), &e.out).await?;673					used_fields.push(index.clone());674					query.push('.');675					let index = format!("${{sess_field_{}}}", index.0.value.expect("value"));676					query.push_str(&index);677				}678				Index::ExprApply(e) => {679					let index = Field::new(self.0.session.clone(), &e.out).await?;680					used_fields.push(index.clone());681					query.push(' ');682					let index = format!("sess_field_{}", index.0.value.expect("value"));683					query.push_str(&index);684					query = format!("({query})");685				}686			}687		}688689		let vid = self690			.0691			.session692			.0693			.lock()694			.await695			.execute_assign(&query)696			.await697			.with_context(|| {698				if let Some(full_path) = &full_path {699					format!("full path: {}", PathDisplay(full_path))700				} else {701					format!("query: {query:?}")702				}703			})?;704		Ok(Self(Arc::new(FieldInner {705			full_path,706			session: self.0.session.clone(),707			value: Some(vid),708		})))709	}710	pub async fn as_json<V: DeserializeOwned>(&self) -> Result<V> {711		let id = self.0.value.expect("can't serialize root field");712		let query = format!("sess_field_{id}");713		self.0714			.session715			.0716			.lock()717			.await718			.execute_expression_to_json(&query)719			.await720			.with_context(|| context(self.0.full_path.as_deref(), &query))721	}722	pub async fn list_fields(&self) -> Result<Vec<String>> {723		let id = self.0.value.expect("can't list root fields");724		let query = format!("builtins.attrNames sess_field_{id}");725		self.0726			.session727			.0728			.lock()729			.await730			.execute_expression_to_json(&query)731			.await732			.with_context(|| context(self.0.full_path.as_deref(), &query))733	}734	pub async fn build(&self) -> Result<HashMap<String, PathBuf>> {735		let id = self.0.value.expect("can't use build on not-value");736		let query = format!(":b sess_field_{id}");737		let vid = self738			.0739			.session740			.0741			.lock()742			.await743			.execute_expression_raw(&query, &mut NixHandler::default())744			.await?;745		ensure!(746			!vid.is_empty(),747			"build failed: {}",748			context(self.0.full_path.as_deref(), &query),749		);750		let Some(vid) = vid.strip_prefix("This derivation produced the following outputs:\n")751		else {752			panic!("unexpected build output: {vid:?}");753		};754		let outputs = vid755			.split('\n')756			.filter(|v| !v.is_empty())757			.map(|v| v.split_once(" -> ").expect("unexpected build output"))758			.map(|(a, b)| (a.trim_start().to_owned(), PathBuf::from(b)))759			.collect();760		Ok(outputs)761	}762}763impl Drop for FieldInner {764	fn drop(&mut self) {765		if let Some(id) = self.value {766			if let Ok(mut lock) = self.session.0.try_lock() {767				lock.free_list.push(id)768			}769			// Leaked770		}771	}772}773struct NixSessionPoolInner {774	flake: OsString,775	nix_args: Vec<OsString>,776}777778#[derive(Debug)]779pub struct NixPoolError(anyhow::Error);780impl From<anyhow::Error> for NixPoolError {781	fn from(value: anyhow::Error) -> Self {782		Self(value)783	}784}785impl std::error::Error for NixPoolError {}786impl std::fmt::Display for NixPoolError {787	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {788		self.0.fmt(f)789	}790}791impl r2d2::ManageConnection for NixSessionPoolInner {792	type Connection = NixSessionInner;793	type Error = NixPoolError;794	fn connect(&self) -> std::result::Result<Self::Connection, Self::Error> {795		let _v = TOKIO_RUNTIME796			.get()797			.expect("missed tokio runtime init!")798			.enter();799		Ok(futures::executor::block_on(NixSessionInner::new(800			self.flake.as_os_str(),801			self.nix_args.iter().map(OsString::as_os_str),802		))?)803	}804805	fn is_valid(&self, conn: &mut Self::Connection) -> std::result::Result<(), Self::Error> {806		let _v = TOKIO_RUNTIME807			.get()808			.expect("missed tokio runtime init!")809			.enter();810		let res = futures::executor::block_on(conn.execute_expression_number("2 + 2"))?;811		if res != 4 {812			return Err(anyhow!("sanity check failed").into());813		};814		Ok(())815	}816817	fn has_broken(&self, _conn: &mut Self::Connection) -> bool {818		false819	}820}821pub struct NixSessionPool(Pool<NixSessionPoolInner>);822impl NixSessionPool {823	pub async fn new(flake: OsString, nix_args: Vec<OsString>) -> Result<Self> {824		let inner = tokio::task::block_in_place(|| {825			r2d2::Builder::<NixSessionPoolInner>::new()826				.min_idle(Some(0))827				.build(NixSessionPoolInner { flake, nix_args })828		})?;829		Ok(Self(inner))830	}831	pub async fn get(&self) -> Result<NixSession> {832		let v = tokio::task::block_in_place(|| self.0.get())?;833		Ok(NixSession(Arc::new(tokio::sync::Mutex::new(v))))834	}835}836837pub static TOKIO_RUNTIME: OnceLock<tokio::runtime::Handle> = OnceLock::new();