Auto merge of #14608 - weihanglo:deserialize, r=epage

refactor(compiler): zero-copy deserialization when possible

src/cargo/core/compiler/job_queue/job_state.rs

@@ -103,7 +103,7 @@ impl<'a, 'gctx> JobState<'a, 'gctx> {
  }
 
  /// See [`Message::Diagnostic`] and [`Message::WarningCount`].
- pub fn emit_diag(&self, level: String, diag: String, fixable: bool) -> CargoResult<()> {
+ pub fn emit_diag(&self, level: &str, diag: String, fixable: bool) -> CargoResult<()> {
  if let Some(dedupe) = self.output {
  let emitted = dedupe.emit_diag(&diag)?;
  if level == "warning" {
@@ -116,7 +116,7 @@ impl<'a, 'gctx> JobState<'a, 'gctx> {
  } else {
  self.messages.push_bounded(Message::Diagnostic {
  id: self.id,
- level,
+ level: level.to_string(),
  diag,
  fixable,
  });

src/cargo/core/compiler/mod.rs

@@ -54,6 +54,7 @@ mod unit;
 pub mod unit_dependencies;
 pub mod unit_graph;
 
+use std::borrow::Cow;
 use std::collections::{HashMap, HashSet};
 use std::env;
 use std::ffi::{OsStr, OsString};
@@ -1756,10 +1757,15 @@ fn on_stderr_line_inner(
  ..
  } => {
  #[derive(serde::Deserialize)]
- struct CompilerMessage {
+ struct CompilerMessage<'a> {
+ // `rendered` contains escape sequences, which can't be
+ // zero-copy deserialized by serde_json.
+ // See https:/serde-rs/json/issues/742
  rendered: String,
- message: String,
- level: String,
+ #[serde(borrow)]
+ message: Cow<'a, str>,
+ #[serde(borrow)]
+ level: Cow<'a, str>,
  children: Vec<PartialDiagnostic>,
  }
 
@@ -1782,7 +1788,8 @@ fn on_stderr_line_inner(
  suggestion_applicability: Option<Applicability>,
  }
 
- if let Ok(mut msg) = serde_json::from_str::<CompilerMessage>(compiler_message.get()) {
+ if let Ok(mut msg) = serde_json::from_str::<CompilerMessage<'_>>(compiler_message.get())
+ {
  if msg.message.starts_with("aborting due to")
  || msg.message.ends_with("warning emitted")
  || msg.message.ends_with("warnings emitted")
@@ -1808,7 +1815,7 @@ fn on_stderr_line_inner(
  })
  .any(|b| b);
  count_diagnostic(&msg.level, options);
- state.emit_diag(msg.level, rendered, machine_applicable)?;
+ state.emit_diag(&msg.level, rendered, machine_applicable)?;
  }
  return Ok(true);
  }
@@ -1819,16 +1826,17 @@ fn on_stderr_line_inner(
  // cached replay to enable/disable colors without re-invoking rustc.
  MessageFormat::Json { ansi: false, .. } => {
  #[derive(serde::Deserialize, serde::Serialize)]
- struct CompilerMessage {
+ struct CompilerMessage<'a> {
  rendered: String,
- #[serde(flatten)]
- other: std::collections::BTreeMap<String, serde_json::Value>,
+ #[serde(flatten, borrow)]
+ other: std::collections::BTreeMap<Cow<'a, str>, serde_json::Value>,
  }
- if let Ok(mut error) = serde_json::from_str::<CompilerMessage>(compiler_message.get()) {
+ if let Ok(mut error) =
+ serde_json::from_str::<CompilerMessage<'_>>(compiler_message.get())
+ {
  error.rendered = anstream::adapter::strip_str(&error.rendered).to_string();
  let new_line = serde_json::to_string(&error)?;
- let new_msg: Box<serde_json::value::RawValue> = serde_json::from_str(&new_line)?;
- compiler_message = new_msg;
+ compiler_message = serde_json::value::RawValue::from_string(new_line)?;
  }
  }
 
@@ -1844,11 +1852,12 @@ fn on_stderr_line_inner(
  // Look for a matching directive and inform Cargo internally that a
  // metadata file has been produced.
  #[derive(serde::Deserialize)]
- struct ArtifactNotification {
- artifact: String,
+ struct ArtifactNotification<'a> {
+ #[serde(borrow)]
+ artifact: Cow<'a, str>,
  }
 
- if let Ok(artifact) = serde_json::from_str::<ArtifactNotification>(compiler_message.get()) {
+ if let Ok(artifact) = serde_json::from_str::<ArtifactNotification<'_>>(compiler_message.get()) {
  trace!("found directive from rustc: `{}`", artifact.artifact);
  if artifact.artifact.ends_with(".rmeta") {
  debug!("looks like metadata finished early!");
@@ -1866,12 +1875,14 @@ fn on_stderr_line_inner(
  }
 
  #[derive(serde::Deserialize)]
- struct CompilerMessage {
- message: String,
- level: String,
+ struct CompilerMessage<'a> {
+ #[serde(borrow)]
+ message: Cow<'a, str>,
+ #[serde(borrow)]
+ level: Cow<'a, str>,
  }
 
- if let Ok(msg) = serde_json::from_str::<CompilerMessage>(compiler_message.get()) {
+ if let Ok(msg) = serde_json::from_str::<CompilerMessage<'_>>(compiler_message.get()) {
  if msg.message.starts_with("aborting due to")
  || msg.message.ends_with("warning emitted")
  || msg.message.ends_with("warnings emitted")