From df5e319d05778e6773e7703dc61fa6baaf4fe3b3 Mon Sep 17 00:00:00 2001
From: Sanjoy Das <sanjoy@google.com>
Date: Sat, 23 May 2020 09:43:17 -0700
Subject: [PATCH] Make the tf2xla "tensor list size not set" error message a
 bit more ergonomic

PiperOrigin-RevId: 312916547
Change-Id: Idbbe406a35205a0fb6dc5e620e04cf3bccefa43d
---
 .../compiler/tf2xla/kernels/tensor_list_ops.cc | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/tensorflow/compiler/tf2xla/kernels/tensor_list_ops.cc b/tensorflow/compiler/tf2xla/kernels/tensor_list_ops.cc
index d01f094dc2e..976ff91f6ce 100644
--- a/tensorflow/compiler/tf2xla/kernels/tensor_list_ops.cc
+++ b/tensorflow/compiler/tf2xla/kernels/tensor_list_ops.cc
@@ -136,8 +136,11 @@ class TensorListReserveOp : public XlaOpKernel {
     OP_REQUIRES_OK(ctx, ctx->ConstantInputAsIntScalar(1, &num_elements));
     OP_REQUIRES(
         ctx, num_elements >= 0,
-        errors::InvalidArgument("XLA compilation requires a fixed tensor list "
-                                "size. Set the number of elements."));
+        errors::InvalidArgument(
+            "XLA compilation requires a fixed tensor list size. Set the number "
+            "of elements. This could also happen if you're using a TensorArray "
+            "in a while loop that does not have its maximum_iteration set, you "
+            "can fix this by setting maximum_iteration to a suitable value."));
 
     // If element shape is compile time constant and it's not "unknown rank"
     // shape (-1), create an initialized TensorList. Otherwise create an
@@ -197,10 +200,13 @@ class EmptyTensorListOp : public XlaOpKernel {
   void Compile(XlaOpKernelContext* ctx) override {
     int64 max_num_elements;
     OP_REQUIRES_OK(ctx, ctx->ConstantInputAsIntScalar(1, &max_num_elements));
-    OP_REQUIRES(
-        ctx, max_num_elements >= 0,
-        errors::InvalidArgument("XLA compilation requires a fixed tensor list "
-                                "size. Set the max number of elements."));
+    OP_REQUIRES(ctx, max_num_elements >= 0,
+                errors::InvalidArgument(
+                    "XLA compilation requires a fixed tensor list size. Set "
+                    "the max number of elements. This could also happen if "
+                    "you're using a TensorArray in a while loop that does not "
+                    "have its maximum_iteration set, you can fix this by "
+                    "setting maximum_iteration to a suitable value."));
 
     if (dtype_ != DT_VARIANT) {
       // We are creating a non-nested TensorList.