Preserve checked I/O failures in tree type adapters

gson/src/main/java/com/google/gson/internal/bind/TreeTypeAdapter.java

@@ -20,6 +20,7 @@
 import com.google.gson.JsonDeserializationContext;
 import com.google.gson.JsonDeserializer;
 import com.google.gson.JsonElement;
+import com.google.gson.JsonIOException;
 import com.google.gson.JsonParseException;
 import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
@@ -88,7 +89,15 @@ public T read(JsonReader in) throws IOException {
     if (deserializer == null) {
       return delegate().read(in);
     }
-    JsonElement value = Streams.parse(in);
+    JsonElement value;
+    try {
+      value = Streams.parse(in);
+    } catch (JsonIOException e) {
+      if (e.getCause() instanceof IOException) {
+        throw (IOException) e.getCause();
+      }
+      throw e;
+    }
     if (nullSafe && value.isJsonNull()) {
       return null;
     }

gson/src/test/java/com/google/gson/functional/TreeTypeAdaptersTest.java

@@ -17,19 +17,28 @@
 package com.google.gson.functional;
 
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
 
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 import com.google.gson.JsonDeserializationContext;
 import com.google.gson.JsonDeserializer;
 import com.google.gson.JsonElement;
+import com.google.gson.JsonIOException;
 import com.google.gson.JsonParseException;
 import com.google.gson.JsonPrimitive;
 import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
+import com.google.gson.JsonSyntaxException;
+import com.google.gson.TypeAdapter;
 import com.google.gson.reflect.TypeToken;
+import java.io.EOFException;
+import java.io.IOException;
+import java.io.Reader;
+import java.io.StringReader;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
+import java.net.SocketTimeoutException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -79,6 +88,55 @@ public void testDeserializeId() {
     assertThat(target.getId().getValue()).isEqualTo("1");
   }
 
+  @Test
+  public void testReadPropagatesIOException() {
+    for (String prefix : Arrays.asList("", "{\"value\":")) {
+      IOException failure = new SocketTimeoutException("response timed out");
+      Reader reader =
+          new StringReader(prefix) {
+            @Override
+            public int read(char[] buffer, int offset, int length) throws IOException {
+              int count = super.read(buffer, offset, length);
+              if (count == -1) {
+                throw failure;
+              }
+              return count;
+            }
+          };
+
+      TypeAdapter<?> adapter = gson.getAdapter(Id.class);
+      IOException actual = assertThrows(IOException.class, () -> adapter.fromJson(reader));
+      assertThat(actual).isSameInstanceAs(failure);
+    }
+  }
+
+  @Test
+  public void testReadPreservesEOFExceptionAsJsonSyntaxException() {
+    TypeAdapter<?> adapter = gson.getAdapter(Id.class);
+    Reader reader = new StringReader("[");
+    JsonSyntaxException actual =
+        assertThrows(JsonSyntaxException.class, () -> adapter.fromJson(reader));
+    assertThat(actual).hasCauseThat().isInstanceOf(EOFException.class);
+  }
+
+  @Test
+  public void testReadPreservesDeserializerException() {
+    JsonIOException failure = new JsonIOException(new IOException("custom deserializer"));
+    Gson customGson =
+        new GsonBuilder()
+            .registerTypeAdapter(
+                Id.class,
+                (JsonDeserializer<Id<?>>)
+                    (json, type, context) -> {
+                      throw failure;
+                    })
+            .create();
+
+    TypeAdapter<?> adapter = customGson.getAdapter(Id.class);
+    JsonIOException actual = assertThrows(JsonIOException.class, () -> adapter.fromJson("1"));
+    assertThat(actual).isSameInstanceAs(failure);
+  }
+
   @SuppressWarnings("UnusedTypeParameter")
   private static final class Id<R> {
     final String value;