fix: write trace files to dedicated directory to avoid breaking formatters

Trace files (trace-*.json) written to the project cwd were picked up by
formatters during E2E tests, causing failures due to truncated JSON.

Add VITE_LOG_OUTPUT_DIR env var to write trace files to a dedicated
directory. Set it in the E2E workflow to ${{ runner.temp }}/trace-artifacts.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: branchseer

.github/workflows/e2e-test.yml

@@ -290,24 +290,22 @@ jobs:
         env:
           VITE_LOG: debug
           VITE_LOG_OUTPUT: chrome-json
+          VITE_LOG_OUTPUT_DIR: ${{ runner.temp }}/trace-artifacts
         run: ${{ matrix.project.command }}
 
       - name: Run vite-plus commands again (cache run) in ${{ matrix.project.name }}
         working-directory: ${{ runner.temp }}/vite-plus-ecosystem-ci/${{ matrix.project.name }}${{ matrix.project.directory && format('/{0}', matrix.project.directory) || '' }}
         env:
           VITE_LOG: debug
           VITE_LOG_OUTPUT: chrome-json
+          VITE_LOG_OUTPUT_DIR: ${{ runner.temp }}/trace-artifacts
         run: ${{ matrix.project.command }}
 
       - name: Collect trace files
         if: always()
         shell: bash
         run: |
           mkdir -p ${{ runner.temp }}/trace-artifacts
-          # Chrome tracing writes trace-*.json in the cwd of the process
-          find ${{ runner.temp }}/vite-plus-ecosystem-ci/${{ matrix.project.name }} -name 'trace-*.json' -exec cp {} ${{ runner.temp }}/trace-artifacts/ \; 2>/dev/null || true
-          # Also check the workspace root
-          find $GITHUB_WORKSPACE -maxdepth 1 -name 'trace-*.json' -exec cp {} ${{ runner.temp }}/trace-artifacts/ \; 2>/dev/null || true
           ls -la ${{ runner.temp }}/trace-artifacts/ 2>/dev/null || echo "No trace files found"
 
       - name: Upload trace artifacts

crates/vite_shared/src/env_vars.rs

@@ -21,6 +21,9 @@ pub const VITE_LOG: &str = "VITE_LOG";
 /// Output mode for tracing (e.g. `"chrome-json"` for Chrome DevTools timeline).
 pub const VITE_LOG_OUTPUT: &str = "VITE_LOG_OUTPUT";
 
+/// Directory for chrome-json trace files (default: current working directory).
+pub const VITE_LOG_OUTPUT_DIR: &str = "VITE_LOG_OUTPUT_DIR";
+
 /// NPM registry URL (lowercase form, highest priority).
 pub const NPM_CONFIG_REGISTRY: &str = "npm_config_registry";
 

crates/vite_shared/src/tracing.rs

@@ -4,8 +4,9 @@
 //! - `VITE_LOG`: Controls log filtering (e.g., `"debug"`, `"vite_task=trace"`)
 //! - `VITE_LOG_OUTPUT`: Output format — `"chrome-json"` for Chrome DevTools timeline,
 //!   `"readable"` for pretty-printed output, or default stdout.
+//! - `VITE_LOG_OUTPUT_DIR`: Directory for chrome-json trace files (default: cwd).
 
-use std::{any::Any, sync::atomic::AtomicBool};
+use std::{any::Any, path::PathBuf, sync::atomic::AtomicBool};
 
 use tracing_chrome::ChromeLayerBuilder;
 use tracing_subscriber::{
@@ -48,10 +49,21 @@ pub fn init_tracing() -> Option<Box<dyn Any + Send>> {
 
     match output_mode.as_str() {
         "chrome-json" => {
-            let (chrome_layer, guard) = ChromeLayerBuilder::new()
+            let mut builder = ChromeLayerBuilder::new()
                 .trace_style(tracing_chrome::TraceStyle::Async)
-                .include_args(true)
-                .build();
+                .include_args(true);
+            // Write trace files to VITE_LOG_OUTPUT_DIR if set, to avoid
+            // polluting the project directory (formatters may pick them up).
+            if let Ok(dir) = std::env::var(env_vars::VITE_LOG_OUTPUT_DIR) {
+                let dir = PathBuf::from(dir);
+                let _ = std::fs::create_dir_all(&dir);
+                let ts = std::time::SystemTime::now()
+                    .duration_since(std::time::UNIX_EPOCH)
+                    .map(|d| d.as_micros())
+                    .unwrap_or(0);
+                builder = builder.file(dir.join(format!("trace-{ts}.json")));
+            }
+            let (chrome_layer, guard) = builder.build();
             tracing_subscriber::registry().with(targets).with(chrome_layer).init();
             Some(Box::new(guard))
         }

performance.md

@@ -273,11 +273,11 @@ vite-task uses Unix shared memory (`/dev/shm`) for parent-child process communic
 
 ## Known Issues
 
-### Windows: Trace files break formatter
+### Trace files break formatter (fixed)
 
-When `VITE_LOG_OUTPUT=chrome-json` is set, trace files (`trace-*.json`) are written to the project working directory. On Windows, `vp fmt` picks up these files and fails with "Unterminated string constant" because the trace files contain very long PATH strings.
+When `VITE_LOG_OUTPUT=chrome-json` is set, trace files (`trace-*.json`) were written to the project working directory. Formatters (oxfmt/prettier) pick up these files and fail with "Unterminated string constant" because trace files may contain truncated JSON (especially on Windows where PATH strings are very long).
 
-**Recommendation**: Add `trace-*.json` to formatter ignore patterns, or write trace files to a dedicated directory outside the workspace.
+**Fix**: Set `VITE_LOG_OUTPUT_DIR` to write trace files to a dedicated directory outside the workspace.
 
 ### NAPI trace files empty for some projects