From ffb1cdcd693673bdde8d6d153a484d61cd8bc14d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roman=20R=C3=A4dle?= <raedle@fb.com>
Date: Tue, 30 Aug 2022 13:40:07 -0700
Subject: [PATCH] Change isNumber check for tensor indexing API (#117)

Summary:
Pull Request resolved: https://github.com/facebookresearch/playtorch/pull/117

The tensor indexing API as implemented before was relying on exceptions when a prop name was not a number. This fails with RN 0.69.x on iOS with the following error:

```
Exception in HostObject::get for prop 'reshape': stoi: no conversion
```

This change implements an `isNumber` function using the `::isdigit` function

Differential Revision: D39141720

fbshipit-source-id: f5e930acfd39285a91fea362116f5297ab72411a
---
 .../src/torchlive/torch/TensorHostObject.cpp  | 41 +++++++++++--------
 1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/react-native-pytorch-core/cxx/src/torchlive/torch/TensorHostObject.cpp b/react-native-pytorch-core/cxx/src/torchlive/torch/TensorHostObject.cpp
index c4a288fc0..3497a3c52 100644
--- a/react-native-pytorch-core/cxx/src/torchlive/torch/TensorHostObject.cpp
+++ b/react-native-pytorch-core/cxx/src/torchlive/torch/TensorHostObject.cpp
@@ -38,6 +38,17 @@ using namespace facebook;
 
 namespace {
 
+/**
+ * Check if the input string is zero or a positive integer.
+ *
+ * @param s String to check for zero or positive integer.
+ * @return `true` if input string is zero or a positive integer, or `false`
+ * otherwise.
+ */
+bool isZeroOrPositiveInteger(const std::string& s) {
+  return !s.empty() && std::all_of(s.begin(), s.end(), ::isdigit);
+}
+
 jsi::Value absImpl(
     jsi::Runtime& runtime,
     const jsi::Value& thisValue,
@@ -702,22 +713,20 @@ jsi::Value TensorHostObject::get(
     return jsi::Value(runtime, toString_);
   }
 
-  int idx = -1;
-  try {
-    idx = std::stoi(name.c_str());
-  } catch (const std::exception& e) {
-    // Cannot parse name value to int. This can happen when the name in bracket
-    // or dot notion is not an int (e.g., tensor['foo']).
-    // Let's ignore this exception here since this function will return
-    // undefined if it reaches the function end.
-  }
-  // Check if index is within bounds of dimension 0
-  if (idx >= 0 && idx < this->tensor.size(0)) {
-    auto outputTensor = this->tensor.index({idx});
-    auto tensorHostObject =
-        std::make_shared<torchlive::torch::TensorHostObject>(
-            runtime, std::move(outputTensor));
-    return jsi::Object::createFromHostObject(runtime, tensorHostObject);
+  // Check if prop name is zero or a positive integer, and if so it will access
+  // the tensor via the tensor indexing API:
+  //
+  // https://pytorch.org/cppdocs/notes/tensor_indexing.html
+  if (isZeroOrPositiveInteger(name)) {
+    int idx = std::stoi(name.c_str());
+    // Check if index is within bounds of dimension 0
+    if (idx >= 0 && idx < this->tensor.size(0)) {
+      auto outputTensor = this->tensor.index({idx});
+      auto tensorHostObject =
+          std::make_shared<torchlive::torch::TensorHostObject>(
+              runtime, std::move(outputTensor));
+      return jsi::Object::createFromHostObject(runtime, tensorHostObject);
+    }
   }
 
   return BaseHostObject::get(runtime, propNameId);