Fix pipe deadlock: drain stdout/stderr concurrently in exec()

Public/index.html

@@ -189,6 +189,7 @@ <h1 class="modal-title fs-5" id="debugger-modal-title">Regex Debugger</h1>
                         <th>Resets</th>
                         <th>Backtracks</th>
                       </tr>
+                    </thead>
                     <tbody>
                       <tr class="font-monospace">
                         <td id="debugger-total-cycle-count">0</td>
@@ -280,7 +281,7 @@ <h1 class="modal-title fs-5" id="debugger-modal-title">Regex Debugger</h1>
         <div class="d-inline-block mx-2">
           <a class="text-reset text-decoration-none small" href="https://github.com/sponsors/kishikawakatsumi"
             target="_blank" rel="nofollow noopener noreferrer">
-            <span class="fa-solid fa-heart" style="color: #bf3989;"></span></span><span class="mx-2">Donate</span></a>
+            <span class="fa-solid fa-heart" style="color: #bf3989;"></span><span class="mx-2">Donate</span></a>
         </div>
       </div>
     </footer>

Public/js/app.js

@@ -79,6 +79,11 @@ export class App {
       this.onDebuggerStepChange();
     });
 
+    const matchStepRange = document.getElementById("debugger-step-range");
+    matchStepRange.addEventListener("input", () => {
+      this.onDebuggerStepChange();
+    });
+
     this.debuggerModal = document.getElementById("debugger-modal");
     this.debuggerModal.addEventListener("shown.bs.modal", () =>
       this.launchDebugger(),
@@ -219,10 +224,6 @@ export class App {
     this.debuggerText.value = text;
 
     this.onDebuggerStepChange();
-
-    matchStepRange.addEventListener("input", (e) => {
-      this.onDebuggerStepChange();
-    });
   }
 
   onExpressionFieldChange() {
@@ -450,7 +451,7 @@ export class App {
 
           const backtracks = document.getElementById("debugger-backtracks");
 
-          const previousBacktracks = backtracks.textContent;
+          const previousBacktracks = Number(backtracks.textContent);
           backtracks.textContent = metrics.backtracks;
 
           this.debuggerText.highlighter.draw(

Sources/App/routes.swift

@@ -187,15 +187,41 @@ func routes(_ app: Application) throws {
     process.standardOutput = standardOutput
     process.standardError = standardError
 
+    var stdoutData = Data()
+    var stderrData = Data()
+    let group = DispatchGroup()
+
+    group.enter()
+    standardOutput.fileHandleForReading.readabilityHandler = { handle in
+      let chunk = handle.availableData
+      if chunk.isEmpty {
+        standardOutput.fileHandleForReading.readabilityHandler = nil
+        group.leave()
+      } else {
+        stdoutData.append(chunk)
+      }
+    }
+
+    group.enter()
+    standardError.fileHandleForReading.readabilityHandler = { handle in
+      let chunk = handle.availableData
+      if chunk.isEmpty {
+        standardError.fileHandleForReading.readabilityHandler = nil
+        group.leave()
+      } else {
+        stderrData.append(chunk)
+      }
+    }
+
     try process.run()
+
+    group.wait()
     process.waitUntilExit()
 
-    let stdoutData = standardOutput.fileHandleForReading.readDataToEndOfFile()
     guard let stdout = String(data: stdoutData, encoding: .utf8) else {
       throw Abort(.internalServerError)
     }
 
-    let stderrData = standardError.fileHandleForReading.readDataToEndOfFile()
     guard let stderr = String(data: stderrData, encoding: .utf8) else {
       throw Abort(.internalServerError)
     }

Sources/ExpressionParser/ExpressionParser.swift

@@ -119,45 +119,36 @@ struct ExpressionParser {
       category = "groups"
       key = "noncapgroup"
     case .nonCaptureReset:
-      groupCount += 1
       category = "groups"
       key = "branchreset"
     case .atomicNonCapturing:
-      groupCount += 1
       category = "groups"
       key = "atomic"
     case .lookahead:
       category = "lookaround"
       key = "poslookahead"
     case .negativeLookahead:
-      groupCount += 1
       category = "lookaround"
       key = "neglookahead"
     case .nonAtomicLookahead:
-      groupCount += 1
       category = "lookaround"
       key = "nonatomicposlookahead"
     case .lookbehind:
       category = "lookaround"
       key = "poslookbehind"
     case .negativeLookbehind:
-      groupCount += 1
       category = "lookaround"
       key = "neglookbehind"
     case .nonAtomicLookbehind:
-      groupCount += 1
       category = "lookaround"
       key = "nonatomicposlookbehind"
     case .scriptRun:
-      groupCount += 1
       category = "Script run. "
       key = ""
     case .atomicScriptRun:
-      groupCount += 1
       category = "Atomic script run. "
       key = ""
     case .changeMatchingOptions(_):
-      groupCount += 1
       category = "Change matching options"
       key = ""
     }