Get diagnostics directly in `rustc-driver-getting-diagnostics` example (#1857)

examples/rustc-driver-getting-diagnostics.rs

@@ -9,12 +9,41 @@ extern crate rustc_interface;
 extern crate rustc_session;
 extern crate rustc_span;
 
-use rustc_errors::registry;
+use rustc_errors::{
+    emitter::Emitter, registry, translation::Translate, DiagCtxt, Diagnostic, FluentBundle,
+};
 use rustc_session::config;
-use std::path;
-use std::process;
-use std::str;
-use std::sync;
+use rustc_span::source_map::SourceMap;
+
+use std::{
+    path, process, str,
+    sync::{Arc, Mutex},
+};
+
+struct DebugEmitter {
+    source_map: Arc<SourceMap>,
+    diagnostics: Arc<Mutex<Vec<Diagnostic>>>,
+}
+
+impl Translate for DebugEmitter {
+    fn fluent_bundle(&self) -> Option<&Arc<FluentBundle>> {
+        None
+    }
+
+    fn fallback_fluent_bundle(&self) -> &FluentBundle {
+        panic!("this emitter should not translate message")
+    }
+}
+
+impl Emitter for DebugEmitter {
+    fn emit_diagnostic(&mut self, diag: &Diagnostic) {
+        self.diagnostics.lock().unwrap().push(diag.clone());
+    }
+
+    fn source_map(&self) -> Option<&Arc<SourceMap>> {
+        Some(&self.source_map)
+    }
+}
 
 fn main() {
     let out = process::Command::new("rustc")
@@ -23,17 +52,11 @@ fn main() {
         .output()
         .unwrap();
     let sysroot = str::from_utf8(&out.stdout).unwrap().trim();
-    let buffer = sync::Arc::new(sync::Mutex::new(Vec::new()));
+    let buffer: Arc<Mutex<Vec<Diagnostic>>> = Arc::default();
+    let diagnostics = buffer.clone();
     let config = rustc_interface::Config {
         opts: config::Options {
             maybe_sysroot: Some(path::PathBuf::from(sysroot)),
-            // Configure the compiler to emit diagnostics in compact JSON format.
-            error_format: config::ErrorOutputType::Json {
-                pretty: false,
-                json_rendered: rustc_errors::emitter::HumanReadableErrorType::Default(
-                    rustc_errors::emitter::ColorConfig::Never,
-                ),
-            },
             ..config::Options::default()
         },
         // This program contains a type error.
@@ -53,7 +76,12 @@ fn main() {
         file_loader: None,
         locale_resources: rustc_driver::DEFAULT_LOCALE_RESOURCES,
         lint_caps: rustc_hash::FxHashMap::default(),
-        parse_sess_created: None,
+        parse_sess_created: Some(Box::new(|parse_sess| {
+            parse_sess.dcx = DiagCtxt::with_emitter(Box::new(DebugEmitter {
+                source_map: parse_sess.clone_source_map(),
+                diagnostics,
+            }))
+        })),
         register_lints: None,
         override_queries: None,
         registry: registry::Registry::new(rustc_error_codes::DIAGNOSTICS),
@@ -61,7 +89,7 @@ fn main() {
         expanded_args: Vec::new(),
         ice_file: None,
         hash_untracked_state: None,
-        using_internal_features: sync::Arc::default(),
+        using_internal_features: Arc::default(),
     };
     rustc_interface::run_compiler(config, |compiler| {
         compiler.enter(|queries| {
@@ -72,6 +100,7 @@ fn main() {
         });
     });
     // Read buffered diagnostics.
-    let diagnostics = String::from_utf8(buffer.lock().unwrap().clone()).unwrap();
-    println!("{diagnostics}");
+    buffer.lock().unwrap().iter().for_each(|diagnostic| {
+        println!("{diagnostic:#?}");
+    });
 }