Don't clear interrupt with Thread.interrupted

Allows caller to spawn a thread, execute, interrupt, and join.

Fixes #1991

CHANGES

@@ -32,6 +32,11 @@ Release 1.16.2 [PENDING]
     ASCII.
     <https://github.com/jhy/jsoup/issues/1952>
 
+  * Bugfix: in Jsoup.connect(url), the ConstrainableInputStream would clear Thread interrupts when reading the body.
+    This precluded callers from spawning a thread, running a number of requests for a length of time, then joining that
+    thread after interrupting it.
+    <https://github.com/jhy/jsoup/issues/1991>
+
   * Change: removed previously deprecated methods Document#normalise, Element#forEach(org.jsoup.helper.Consumer<>),
     Node#forEach(org.jsoup.helper.Consumer<>), and the org.jsoup.helper.Consumer interface; the latter being a
     previously required compatibility shim prior to Android's de-sugaring support.

src/main/java/org/jsoup/internal/ConstrainableInputStream.java

@@ -49,8 +49,8 @@ public static ConstrainableInputStream wrap(InputStream in, int bufferSize, int
     public int read(byte[] b, int off, int len) throws IOException {
         if (interrupted || capped && remaining <= 0)
             return -1;
-        if (Thread.interrupted()) {
-            // interrupted latches, because parse() may call twice (and we still want the thread interupt to clear)
+        if (Thread.currentThread().isInterrupted()) {
+            // interrupted latches, because parse() may call twice
             interrupted = true;
             return -1;
         }

src/test/java/org/jsoup/integration/ConnectIT.java

@@ -14,6 +14,7 @@
 import java.net.SocketTimeoutException;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -70,7 +71,29 @@ public void canInterruptDocumentRead() throws InterruptedException {
         assertTrue(runner.isInterrupted());
         runner.join();
 
-        assertEquals(0, body[0].length()); // doesn't ready a failed doc
+        assertEquals(0, body[0].length()); // doesn't read a failed doc
+    }
+
+    @Test public void canInterruptThenJoinASpawnedThread() throws InterruptedException {
+        // https://github.com/jhy/jsoup/issues/1991
+        AtomicBoolean ioException = new AtomicBoolean();
+        Thread runner = new Thread(() -> {
+            try {
+                while (!Thread.currentThread().isInterrupted()) {
+                    Document doc  = Jsoup.connect(SlowRider.Url)
+                        .timeout(4000)
+                        .get();
+                }
+            } catch (IOException e) {
+                ioException.set(true); // don't expect to catch, because the outer sleep will complete before this timeout
+            }
+        });
+
+        runner.start();
+        Thread.sleep(2 * 1000);
+        runner.interrupt();
+        runner.join();
+        assertFalse(ioException.get());
     }
 
     @Test