Preserve printf-style format substitution when piping server logs to browser console - #479
Preserve printf-style format substitution when piping server logs to browser console#479mvanhorn wants to merge 1 commit into
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WalkthroughThe virtual console SSE log renderer in devtools-vite is updated to detect printf-style format substitutions (%s, %c) in server log arguments and preserve them when injecting the [Server] prefix. transformServerLogArgs gains a preserveEmptyStrings flag, and new client-side helpers compute a formatIndex that controls how the prefix is spliced in. Tests are refactored and extended to cover all substitution cases. ChangesServer log format-substitution preservation
Estimated code review effort🎯 2 (Simple) | ⏱️ ~10 minutes Poem🚥 Pre-merge checks | ✅ 4 | ❌ 1 ❌ Failed checks (1 warning)
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Actionable comments posted: 1
🤖 Prompt for all review comments with AI agentsVerify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. Inline comments: In `@packages/devtools-vite/src/virtual-console.ts`: - Around line 321-324: The preserve-format detection in getConsoleFormatIndex is too permissive and can treat literal percent text like “100%c” as a format string when there are no matching substitution arguments. Update the logic around getConsoleFormatIndex and the related preserve-format path to only preserve formatting when the number of actual console placeholders is supported by the available trailing args, so literal % sequences are not reclassified after prefix injection.
Fix all unresolved CodeRabbit comments on this PR:
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- Create a new PR with the fixes
ℹ️ Review info ⚙️ Run configuration
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Run ID: 37abba98-2a17-4807-b0ce-73c14e43479c
📥 CommitsReviewing files that changed from the base of the PR and between e026667 and 2cc1dda.
📒 Files selected for processing (3)- .changeset/fresh-mails-bow.md
- packages/devtools-vite/src/virtual-console.test.ts
- packages/devtools-vite/src/virtual-console.ts
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| function getConsoleFormatIndex(args) { | ||
| if (hasConsoleFormatSubstitution(args[0])) return 0; | ||
| return isEnhancedLogPrefix(args[0]) && hasConsoleFormatSubstitution(args[1]) ? 1 : -1; | ||
| } |
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🎯 Functional Correctness | 🟠 Major | ⚡ Quick win
Avoid classifying literal % sequences as format substitutions.
getConsoleFormatIndex currently enables the preserve-format branch even when there are no substitution arguments. Literal messages like "CPU at 100%c" can then be treated as format strings and rendered incorrectly after prefix injection. Gate preservation by placeholder count vs available trailing args.
Suggested fix- function hasConsoleFormatSubstitution(arg) {
- return typeof arg === 'string' && /(^|[^%])%[sdifocOj]/.test(arg);
- }
+ function getConsoleFormatPlaceholderCount(arg) {
+ if (typeof arg !== 'string') return 0;
+ var matches = arg.match(/(^|[^%])%[sdifocOj]/g);
+ return matches ? matches.length : 0;
+ }
function isEnhancedLogPrefix(arg) {
return typeof arg === 'string' &&
arg.indexOf('LOG') !== -1 &&
arg.indexOf(String.fromCharCode(10) + ' ' + String.fromCharCode(8594) + ' ') !== -1;
}
+ function hasResolvableConsoleFormatSubstitution(args, formatIndex) {
+ var placeholderCount = getConsoleFormatPlaceholderCount(args[formatIndex]);
+ return placeholderCount > 0 && (args.length - (formatIndex + 1)) >= placeholderCount;
+ }
+
function getConsoleFormatIndex(args) {
- if (hasConsoleFormatSubstitution(args[0])) return 0;
- return isEnhancedLogPrefix(args[0]) && hasConsoleFormatSubstitution(args[1]) ? 1 : -1;
+ if (hasResolvableConsoleFormatSubstitution(args, 0)) return 0;
+ return isEnhancedLogPrefix(args[0]) && hasResolvableConsoleFormatSubstitution(args, 1) ? 1 : -1;
}Also applies to: 334-336
🤖 Prompt for AI AgentsVerify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@packages/devtools-vite/src/virtual-console.ts` around lines 321 - 324, The preserve-format detection in getConsoleFormatIndex is too permissive and can treat literal percent text like “100%c” as a format string when there are no matching substitution arguments. Update the logic around getConsoleFormatIndex and the related preserve-format path to only preserve formatting when the number of actual console placeholders is supported by the available trailing args, so literal % sequences are not reclassified after prefix injection.
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🎯 Changes
Server log messages that use console format strings (%s, %d, %c, etc.) are now substituted correctly when forwarded to the browser devtools console, including the default enhanced-logs path where the source-location prefix sits before the user's arguments. Previously the format string was passed through as a plain argument, so substitutions were not applied and the raw %s tokens appeared in the panel.
The SSE bridge that forwards server-side console.log/console.error did not detect format strings in all cases: with enhanced logs enabled (the default), enhanceConsoleLog prepends a LOG /path:line:col prefix, so the real format string was no longer the first argument and the substitution path was skipped. This now accounts for the enhanced-log prefix, the direct SSE path, and the %c/empty-argument edge cases. Closes #435.
✅ Checklist
🚀 Release Impact
Summary by CodeRabbit
New Features
Bug Fixes