Add -Zerror-metrics=PATH to save diagnostic metadata to disk

Author: yaahc

.gitignore

@@ -19,6 +19,7 @@ Session.vim
 *.iml
 .vscode
 .project
+.vim/
 .favorites.json
 .settings/
 .vs/

compiler/rustc_driver_impl/src/lib.rs

@@ -51,7 +51,8 @@ use rustc_metadata::creader::MetadataLoader;
 use rustc_metadata::locator;
 use rustc_parse::{new_parser_from_file, new_parser_from_source_str, unwrap_or_emit_fatal};
 use rustc_session::config::{
-    nightly_options, ErrorOutputType, Input, OutFileName, OutputType, CG_OPTIONS, Z_OPTIONS,
+    nightly_options, ErrorOutputType, Input, OutFileName, OutputType, UnstableOptions, CG_OPTIONS,
+    Z_OPTIONS,
 };
 use rustc_session::getopts::{self, Matches};
 use rustc_session::lint::{Lint, LintId};
@@ -301,6 +302,8 @@ fn run_compiler(
     let Some(matches) = handle_options(&default_early_dcx, &args) else { return Ok(()) };
 
     let sopts = config::build_session_options(&mut default_early_dcx, &matches);
+    // fully initialize ice path static once unstable options are available as context
+    let ice_file = ice_path_with_config(Some(&sopts.unstable_opts));
 
     if let Some(ref code) = matches.opt_str("explain") {
         handle_explain(&default_early_dcx, diagnostics_registry(), code, sopts.color);
@@ -315,7 +318,7 @@ fn run_compiler(
         input: Input::File(PathBuf::new()),
         output_file: ofile,
         output_dir: odir,
-        ice_file: ice_path().clone(),
+        ice_file,
         file_loader,
         locale_resources: DEFAULT_LOCALE_RESOURCES,
         lint_caps: Default::default(),
@@ -357,7 +360,11 @@ fn run_compiler(
         // printing some information without compiling, or exiting immediately
         // after parsing, etc.
         let early_exit = || {
-            if let Some(guar) = sess.dcx().has_errors() { Err(guar) } else { Ok(()) }
+            if let Some(guar) = sess.dcx().has_errors() {
+                Err(guar)
+            } else {
+                Ok(())
+            }
         };
 
         // This implements `-Whelp`. It should be handled very early, like
@@ -567,7 +574,11 @@ fn handle_explain(early_dcx: &EarlyDiagCtxt, registry: Registry, code: &str, col
 fn show_md_content_with_pager(content: &str, color: ColorConfig) {
     let mut fallback_to_println = false;
     let pager_name = env::var_os("PAGER").unwrap_or_else(|| {
-        if cfg!(windows) { OsString::from("more.com") } else { OsString::from("less") }
+        if cfg!(windows) {
+            OsString::from("more.com")
+        } else {
+            OsString::from("less")
+        }
     });
 
     let mut cmd = Command::new(&pager_name);
@@ -1306,16 +1317,26 @@ pub fn catch_with_exit_code(f: impl FnOnce() -> interface::Result<()>) -> i32 {
 
 static ICE_PATH: OnceLock<Option<PathBuf>> = OnceLock::new();
 
+// This function should only be called from the ICE hook.
+//
+// The intended behavior is that `run_compiler` will invoke `ice_path_with_config` early in the
+// initialization process to properly initialize the ICE_PATH static based on parsed CLI flags.
+//
+// Subsequent calls to either function will then return the proper ICE path as configured by
+// the environment and cli flags
 fn ice_path() -> &'static Option<PathBuf> {
+    ice_path_with_config(None)
+}
+
+fn ice_path_with_config(config: Option<&UnstableOptions>) -> &'static Option<PathBuf> {
+    if ICE_PATH.get().is_some() && config.is_some() && cfg!(debug_assertions) {
+        warn!("ICE_PATH has already been initialized -- files may be emitted at unintended paths")
+    }
+
     ICE_PATH.get_or_init(|| {
         if !rustc_feature::UnstableFeatures::from_environment(None).is_nightly_build() {
             return None;
         }
-        if let Some(s) = std::env::var_os("RUST_BACKTRACE")
-            && s == "0"
-        {
-            return None;
-        }
         let mut path = match std::env::var_os("RUSTC_ICE") {
             Some(s) => {
                 if s == "0" {
@@ -1324,7 +1345,10 @@ fn ice_path() -> &'static Option<PathBuf> {
                 }
                 PathBuf::from(s)
             }
-            None => std::env::current_dir().unwrap_or_default(),
+            None => config
+                .and_then(|unstable_opts| unstable_opts.error_metrics.to_owned())
+                .or_else(|| std::env::current_dir().ok())
+                .unwrap_or_default(),
         };
         let now: OffsetDateTime = SystemTime::now().into();
         let file_now = now

compiler/rustc_session/src/options.rs

@@ -1714,6 +1714,8 @@ options! {
         "emit the bc module with thin LTO info (default: yes)"),
     enforce_type_length_limit: bool = (false, parse_bool, [TRACKED],
         "enforce the type length limit when monomorphizing instances in codegen"),
+    error_metrics: Option<PathBuf> = (None, parse_opt_pathbuf, [UNTRACKED],
+        "stores metrics about the errors being emitted by rustc to disk"),
     export_executable_symbols: bool = (false, parse_bool, [TRACKED],
         "export symbols from executables, as if they were dynamic libraries"),
     external_clangrt: bool = (false, parse_bool, [UNTRACKED],