fix: webtau step handles large amount of details without crash (#1651)

Author: MykolaGolubyev

webtau-core/src/main/java/org/testingisdocumenting/webtau/reporter/TokenizedMessageToAnsiConverter.java

@@ -103,7 +103,7 @@ private Stream<?> ansiSequenceFromPrettyPrinter(ValueConverter valueConverter, P
         printer.printObject(value);
         printer.flushCurrentLine();
 
-        Stream<Object> result = Stream.empty();
+        Stream.Builder<Object> result = Stream.builder();
 
         String indentation = StringUtils.createIndentation(currentLine.hasNewLine() ?
                 currentLine.findWidthOfTheLastEffectiveLine():
@@ -118,24 +118,24 @@ private Stream<?> ansiSequenceFromPrettyPrinter(ValueConverter valueConverter, P
             boolean isLastLine = idx == printer.getNumberOfLines() - 1;
             PrettyPrinterLine line = printer.getLine(idx);
 
-            if (isFirstLine) {
-                result = Stream.concat(result, line.getStyleAndValues().stream());
-            } else {
-                result = Stream.concat(result, Stream.concat(
-                        Stream.of(indentation),
-                        line.getStyleAndValues().stream()));
+            if (!isFirstLine) {
+                result.add(indentation);
             }
 
+            line.getStyleAndValues().forEach(result::add);
+
             if (!isLastLine) {
-                result = Stream.concat(result, Stream.of("\n"));
+                result.add("\n");
             }
         }
 
         if (numberOfLinesToPrint > 1 && numberOfLinesToPrint != printer.getNumberOfLines()) {
-            result = Stream.concat(result, Stream.of(PrettyPrinter.DELIMITER_COLOR, indentation, "..."));
+            result.add(PrettyPrinter.DELIMITER_COLOR);
+            result.add(indentation);
+            result.add("...");
         }
 
-        return result;
+        return result.build();
     }
 
     private void associateDefaultTokens() {

webtau-core/src/main/java/org/testingisdocumenting/webtau/reporter/WebTauStep.java

@@ -306,7 +306,20 @@ public void setValueConverter(ValueConverter valueConverter) {
     }
 
     public Stream<WebTauStepOutput> collectOutputs() {
-        return Stream.concat(outputs.stream(), children.stream().flatMap(WebTauStep::collectOutputs));
+        List<WebTauStepOutput> result = new ArrayList<>();
+        Deque<WebTauStep> stack = new ArrayDeque<>();
+        stack.push(this);
+
+        while (!stack.isEmpty()) {
+            WebTauStep step = stack.pop();
+            result.addAll(step.outputs);
+
+            for (int i = step.children.size() - 1; i >= 0; i--) {
+                stack.push(step.children.get(i));
+            }
+        }
+
+        return result.stream();
     }
 
     @SuppressWarnings("unchecked")
@@ -321,10 +334,22 @@ public boolean hasOutput(Class<? extends WebTauStepOutput> type) {
     }
 
     public Stream<WebTauStep> stepsWithClassifier(String classifier) {
-        Stream<WebTauStep> self = this.classifier.equals(classifier) ? Stream.of(this) : Stream.empty();
-        Stream<WebTauStep> children = children().flatMap(childStep -> childStep.stepsWithClassifier(classifier));
+        List<WebTauStep> result = new ArrayList<>();
+        Deque<WebTauStep> stack = new ArrayDeque<>();
+        stack.push(this);
+
+        while (!stack.isEmpty()) {
+            WebTauStep step = stack.pop();
+            if (step.classifier.equals(classifier)) {
+                result.add(step);
+            }
+
+            for (int i = step.children.size() - 1; i >= 0; i--) {
+                stack.push(step.children.get(i));
+            }
+        }
 
-        return Stream.concat(self, children);
+        return result.stream();
     }
 
     public boolean hasFailedChildrenSteps() {

webtau-core/src/test/groovy/org/testingisdocumenting/webtau/reporter/TokenizedMessageToAnsiConverterTest.groovy

@@ -41,4 +41,18 @@ class TokenizedMessageToAnsiConverterTest {
         def ansiSequence = new AutoResetAnsiString(valuesAndStyles.stream()).toString()
         actual(ansiSequence).should(equal("\u001B[1m\u001B[36mhello \u001B[0m\u001B[34mworld \u001B[1m\u001B[33mworld\u001B[0m"))
     }
+
+    @Test
+    void "should handle large pretty printed value without stack overflow"() {
+        def converter = TokenizedMessageToAnsiConverter.DEFAULT
+        def largeList = (1..6000).collect { it }
+        def message = new TokenizedMessage().value(largeList)
+
+        def valuesAndStyles = converter.convert(ValueConverter.EMPTY, message, 0)
+        
+        def ansiString = new AutoResetAnsiString(valuesAndStyles.stream()).toString()
+        def plainString = ansiString.replaceAll(/\u001B\[[;0-9]*m/, "")
+        def expected = "[\n  " + largeList.join(",\n  ") + "\n]"
+        actual(plainString).should(equal(expected))
+    }
 }

webtau-core/src/test/groovy/org/testingisdocumenting/webtau/reporter/WebTauStepTest.groovy

@@ -269,6 +269,36 @@ class WebTauStepTest {
         }
     }
 
+    @Test
+    void "recursion methods should not cause stack overflow on deep trees"() {
+        def root = createStep("root")
+        def current = root
+        def stepsToExecute = []
+
+        int depth = 2000
+        depth.times { idx ->
+            def child = WebTauStep.createStepWithExplicitParent(current, 0,
+                    tokenizedMessage().action("child #" + idx),
+                    { Object ignored -> tokenizedMessage().action("done child #" + idx) },
+              { WebTauStepContext context -> return null })
+            child.setClassifier("test")
+            child.addOutput(new OutputA(id: "out" + idx))
+            stepsToExecute.add(child)
+            current = child
+        }
+
+        stepsToExecute.reverseEach { it.execute(SKIP_ALL) }
+        root.execute(SKIP_ALL)
+
+        def steps = root.stepsWithClassifier("test").collect(toList())
+        assert steps.size() == depth
+        assert steps.inProgressMessage*.toString() == (0..<depth).collect { "child #$it" }
+
+        def outputs = root.collectOutputs().collect(toList())
+        assert outputs.size() == depth
+        assert outputs*.toMap() == (0..<depth).collect { [id: "out$it"] }
+    }
+
     private static WebTauStep createStep(String title, Supplier stepCode = { return null }) {
         return WebTauStep.createStep(tokenizedMessage().action(title), {
             tokenizedMessage().action('done ' + title)

webtau-docs/znai/release-notes/2.6/fix-2026-01-11-step-large-details-stack-overflow.md

@@ -0,0 +1 @@
+* Fix: WebTau step now handles large amount of details without stack overflow error.

webtau-docs/znai/release-notes/2026.md

@@ -0,0 +1,7 @@
+---
+title: 2026 Releases
+---
+
+# 2.6
+
+:include-markdowns: 2.6