Preserve invocation order in RemoteInputConnection

This is a follow up CL to our previous CL [1], which introduced
early-exit paths to some RemoteInputConnection methods to protect
innocent IME clients from unexpected process crashes when an IME is
calling InputConnection APIs with invalid parameters.

Although protecting IME clients from crashes still makes much sense,
implementing it as an early-exit style in RemoteInputConnection may
expose observable inconsistency to IME developers in terms of the fact
that InputConnection#getText{Before,After}Cursor() can also work as a
fence operation that would not return until all the previously issued
InputConnection API invocations are handled in the IME client side.

With this CL, the following methods start behaving as a fence
operation even when an invalid parameter is passed, by checking the
parameters in the IME client side.

 * RemoteInputConnection#getTextAfterCursor()
 * RemoteInputConnection#getTextBeforeCursor()
 * RemoteInputConnection#getSurroundingText()

There should be no performance impact for IMEs that do not make such
an invalid (and unnecessary) API calls.

 [1]: I95169735198f8363c981a61e20234dfebfd645b1
      1e72ef2893

Bug: 169114026
Fix: 194110780
Test: atest CtsInputMethodTestCases:InputConnectionEndToEndTest
Change-Id: Ie0c18d0c9b8bf8f02f2fcdca5aac7e580c6bf2cd

core/java/android/inputmethodservice/RemoteInputConnection.java

@@ -108,7 +108,11 @@ final class RemoteInputConnection implements InputConnection {
     @Nullable
     @AnyThread
     public CharSequence getTextAfterCursor(@IntRange(from = 0) int length, int flags) {
-        if (length < 0 || mCancellationGroup.isCanceled()) {
+        if (length < 0) {
+            // TODO: Should we throw an InvalidParameterException() based on targetSdkVersion?
+            Log.e(TAG, "length=" + length + " is invalid and always results in null result.");
+        }
+        if (mCancellationGroup.isCanceled()) {
             return null;
         }
 
@@ -132,7 +136,11 @@ final class RemoteInputConnection implements InputConnection {
     @Nullable
     @AnyThread
     public CharSequence getTextBeforeCursor(@IntRange(from = 0) int length, int flags) {
-        if (length < 0 || mCancellationGroup.isCanceled()) {
+        if (length < 0) {
+            // TODO: Should we throw an InvalidParameterException() based on targetSdkVersion?
+            Log.e(TAG, "length=" + length + " is invalid and always results in null result.");
+        }
+        if (mCancellationGroup.isCanceled()) {
             return null;
         }
 
@@ -185,7 +193,17 @@ final class RemoteInputConnection implements InputConnection {
     @AnyThread
     public SurroundingText getSurroundingText(
             @IntRange(from = 0) int beforeLength, @IntRange(from = 0) int afterLength, int flags) {
-        if (beforeLength < 0 || afterLength < 0 || mCancellationGroup.isCanceled()) {
+        if (beforeLength < 0) {
+            // TODO: Should we throw an InvalidParameterException() based on targetSdkVersion?
+            Log.e(TAG, "beforeLength=" + beforeLength
+                    + " is invalid and always results in null result.");
+        }
+        if (afterLength < 0) {
+            // TODO: Should we throw an InvalidParameterException() based on targetSdkVersion?
+            Log.e(TAG, "afterLength=" + afterLength
+                    + " is invalid and always results in null result.");
+        }
+        if (mCancellationGroup.isCanceled()) {
             return null;
         }
 

core/java/com/android/internal/inputmethod/RemoteInputConnectionImpl.java

@@ -233,6 +233,11 @@ public final class RemoteInputConnectionImpl extends IInputContext.Stub {
                 Log.w(TAG, "getTextAfterCursor on inactive InputConnection");
                 return null;
             }
+            if (length < 0) {
+                Log.i(TAG, "Returning null to getTextAfterCursor due to an invalid length="
+                        + length);
+                return null;
+            }
             return ic.getTextAfterCursor(length, flags);
         }, useImeTracing() ? result -> buildGetTextAfterCursorProto(length, flags, result) : null);
     }
@@ -246,6 +251,11 @@ public final class RemoteInputConnectionImpl extends IInputContext.Stub {
                 Log.w(TAG, "getTextBeforeCursor on inactive InputConnection");
                 return null;
             }
+            if (length < 0) {
+                Log.i(TAG, "Returning null to getTextBeforeCursor due to an invalid length="
+                        + length);
+                return null;
+            }
             return ic.getTextBeforeCursor(length, flags);
         }, useImeTracing() ? result -> buildGetTextBeforeCursorProto(length, flags, result) : null);
     }
@@ -276,6 +286,16 @@ public final class RemoteInputConnectionImpl extends IInputContext.Stub {
                 Log.w(TAG, "getSurroundingText on inactive InputConnection");
                 return null;
             }
+            if (beforeLength < 0) {
+                Log.i(TAG, "Returning null to getSurroundingText due to an invalid"
+                        + " beforeLength=" + beforeLength);
+                return null;
+            }
+            if (afterLength < 0) {
+                Log.i(TAG, "Returning null to getSurroundingText due to an invalid"
+                        + " afterLength=" + afterLength);
+                return null;
+            }
             return ic.getSurroundingText(beforeLength, afterLength, flags);
         }, useImeTracing() ? result -> buildGetSurroundingTextProto(
                 beforeLength, afterLength, flags, result) : null);