feat(#3840): identify concurrency issue

Author: volodya-lombrozo

eo-parser/src/main/java/org/eolang/parser/TrStepped.java

@@ -54,19 +54,24 @@ final class TrStepped extends TrEnvelope {
         )
     );
 
+    TrStepped(final Train<Shift> train) {
+        this(train, TrStepped.STEPPED);
+    }
+
     /**
      * Ctor.
+     *
      * @param train Original train
      */
-    TrStepped(final Train<Shift> train) {
+    TrStepped(final Train<Shift> train, Scalar<XSL> stepped) {
         super(
             new TrLambda(
                 train,
                 shift -> new StAfter(
                     shift,
                     new StLambda(
                         shift::uid,
-                        (pos, xml) -> TrStepped.STEPPED.value()
+                        (pos, xml) -> stepped.value()
                             .with("step", pos)
                             .with("sheet", shift.uid())
                             .transform(xml)

eo-parser/src/test/java/org/eolang/parser/TrSteppedTest.java

@@ -26,11 +26,24 @@
 import com.jcabi.matchers.XhtmlMatchers;
 import com.jcabi.xml.XML;
 import com.jcabi.xml.XMLDocument;
+import com.jcabi.xml.XSL;
+import com.jcabi.xml.XSLDocument;
+import com.yegor256.Together;
 import com.yegor256.xsline.Shift;
 import com.yegor256.xsline.StClasspath;
 import com.yegor256.xsline.TrDefault;
+import com.yegor256.xsline.Train;
 import com.yegor256.xsline.Xsline;
+import java.io.InputStream;
+import java.net.URLClassLoader;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicReference;
+import org.cactoos.Input;
+import org.cactoos.io.ResourceOf;
+import org.cactoos.scalar.Sticky;
+import org.cactoos.text.TextOf;
 import org.hamcrest.MatcherAssert;
+import org.junit.jupiter.api.RepeatedTest;
 import org.junit.jupiter.api.Test;
 
 /**
@@ -49,11 +62,44 @@ void addsSheetName() {
                     new TrDefault<Shift>().with(
                         new StClasspath("/org/eolang/parser/print/wrap-data.xsl"))
                 )).pass(
-                new XMLDocument("<program><language>EO</language></program>")
+                new XMLDocument("<program><concurrency>no</concurrency></program>")
             ).toString(),
             XhtmlMatchers.hasXPath("/program/sheets/sheet[text()='wrap-data']")
         );
     }
 
+    @RepeatedTest(10)
+    void addsSheetNameConcurrently() {
+        final XML doc = new XMLDocument("<program><concurrency>yes</concurrency></program>");
+        final CountDownLatch once = new CountDownLatch(1);
+        final Sticky<XSL> loading = new Sticky<>(
+            () -> {
+                if (once.getCount() == 0) {
+                    throw new IllegalStateException("Resource should be loaded only once");
+                }
+                once.countDown();
+                return new XSLDocument(
+                    new TextOf(
+                        () -> new ResourceOf("org/eolang/parser/_stepped.xsl").stream()
+                    ).asString()
+                );
+            }
+        );
+        MatcherAssert.assertThat(
+            "We expect the sheet name to be added successfully in concurrent environment",
+            new Together<>(
+                i -> new Xsline(
+                    new TrStepped(
+                        new TrDefault<Shift>().with(
+                            new StClasspath("/org/eolang/parser/print/wrap-data.xsl")
+                        ),
+                        loading
+                    )
+                ).pass(doc).toString()
+            ).iterator().next(),
+            XhtmlMatchers.hasXPath("/program/sheets/sheet[text()='wrap-data']")
+        );
+    }
+
 
 }