Update instruction to install flatc (#447)

Summary:
Pull Request resolved: #447

See context in D49487908, the `flatc` from `brew install flatbuffers` seems good.

config change is in D49780588

Reviewed By: dbort

Differential Revision: D49530021

fbshipit-source-id: 7891c03ad82281253451bcca700251d17174f4ac

Author: cccclai

build/install_flatc.sh

@@ -0,0 +1,58 @@
+#!/bin/bash
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+# This file is meant to build flatc from the `third-party/flatbuffers` folder and help
+# users to ensure it's installed correctly
+
+ROOT=$(cd -- "$(dirname "$(dirname -- "${BASH_SOURCE[0]}")")" &> /dev/null && pwd)
+FLATBUFFERS_PATH="$ROOT/third-party/flatbuffers"
+
+# Get the flatbuffers version from the git submodule
+get_flatbuffers_version(){
+    pushd "$FLATBUFFERS_PATH" || exit
+    FLATBUFFERS_VERSION=$(git describe --tags "$(git rev-list --tags --max-count=1)" | sed 's/^v//')
+    popd || exit
+}
+
+FLATC_PATH="$(which flatc 2>&1)"
+
+GREEN='\033[0;32m' # GREEN Color
+RED='\033[0;31m' # Red Color
+NC='\033[0m' # No Color
+
+get_flatbuffers_version
+echo "flatbuffers version in $FLATBUFFERS_PATH is: $FLATBUFFERS_VERSION"
+
+# Warn the users to uninstall flatc from conda
+if [[ "$FLATC_PATH" == *miniconda3* ]]; then
+    echo "${RED}From the flatc path: $FLATC_PATH, it seems it's installed with conda. The flatc from conda is problematic and please avoid using it."
+    echo "Please run the following lines to remove it: "
+    echo "    conda uninstall flatbuffers"
+    exit
+fi
+
+# Check the following:
+# 1. the path to the flatc command if it exists in the system's PATH
+# 2. execute the flatc command and check the version
+if { command -v flatc; } && { flatc --version | grep "$FLATBUFFERS_VERSION" &> /dev/null; }; then
+    echo "${GREEN}flatc is installed successfully and ready to use. ${NC}"
+else
+    # Check the existence of flatc in flatbuffers path, if it exists, instruct users to export it to path
+    if [[ -f "$FLATBUFFERS_PATH/flatc" ]]; then
+        echo "${RED}flatc is built in $FLATBUFFERS_PATH/flatc but hasn't added to path, run following lines: "
+        echo " export PATH=$FLATBUFFERS_PATH:\$PATH ${NC}"
+    else
+        # flatc is not in flatbuffers path, build it and instruct users to export it to path
+        pushd "$FLATBUFFERS_PATH" || exit
+        cmake --build . --target flatc
+        echo "flatc path: $FLATBUFFERS_PATH/flatc"
+        popd || exit
+        echo "${RED}Finished building flatc. Run the following lines to add it to PATH, then re-run this script:"
+        echo " export PATH=\"$FLATBUFFERS_PATH:\$PATH\" "
+        echo " bash build/install_flatc.sh${NC}"
+    fi
+fi

docs/source/getting-started-setup.md

@@ -65,12 +65,6 @@ the steps in the [conda installation guide](https://conda.io/projects/conda/en/l
    conda activate executorch
    ```
 
-1. Install the flatbuffers `flatc` command line tool if you do not already have it:
-
-   ```bash
-   conda install -c conda-forge flatbuffers
-   ```
-
 1. Clone the `executorch` repository:
 
    ```bash

docs/website/docs/tutorials/cmake_build_system.md

@@ -122,12 +122,22 @@ Assuming NDK is available on installed, run
 # Run the following lines from executorch folder
 rm -rf cmake-android-out && mkdir cmake-android-out && cd cmake-android-out
 
-# point -DCMAKE_TOOLCHAIN_FILE to the location where ndk is installed
-# Run `which buck2`, if it returns empty (meaning the system doesn't know where buck2 is installed), pass in pass in this flag `-DBUCK2=/path/to/buck2` pointing to buck2
-cmake -DCMAKE_TOOLCHAIN_FILE=/Users/{user_name}/Library/Android/sdk/ndk/25.2.9519653/build/cmake/android.toolchain.cmake  -DANDROID_ABI=arm64-v8a ..
-
-cd  ..
-cmake --build  cmake-android-out  -j9
+BUCK2=/path/to/buck2
+FLATC=/path/to/flatc
+NDK_ROOT=${HOME}/Library/Android/sdk/ndk/25.2.9519653
+
+# Point -DCMAKE_TOOLCHAIN_FILE to the location where ndk is installed.
+# If BUCK2 or FLATC aren't specified, fall back to using
+# the commands on the PATH.
+cmake \
+  -DCMAKE_TOOLCHAIN_FILE=${NDK_ROOT}/build/cmake/android.toolchain.cmake \
+  -DANDROID_ABI=arm64-v8a \
+  -DBUCK2="${BUCK2:-$(which buck2)}" \
+  -DFLATC_EXECUTABLE="${FLATC:-$(which flatc)}" \
+  ..
+
+# Move to the executorch folder and build
+cd .. && cmake --build cmake-android-out -j9
 
 # push the binary to an Android device
 adb push  cmake-android-out/executor_runner  /data/local/tmp/executorch
@@ -162,14 +172,28 @@ git clone  https://github.com/leetal/ios-cmake.git
 ```bash
 rm -rf cmake-ios-out && mkdir cmake-ios-out && cd cmake-ios-out
 
-# change the platform accordingly, please refer to the table listed in Readme
-cmake . -G Xcode -DCMAKE_TOOLCHAIN_FILE=~/ios-cmake/ios.toolchain.cmake -DPLATFORM=SIMULATOR
+BUCK2=/path/to/buck2
+FLATC=/path/to/flatc
+PYTHON=/path/to/miniconda/envs/executorch/bin/python3
+# The path to the cloned ios-cmake repo
+IOS_CMAKE=/path/to/ios-cmake
+
+# Change the PLATFORM accordingly; please refer to the table listed in https://github.com/leetal/ios-cmake#readme
+cmake \
+  -G Xcode \
+  -DCMAKE_TOOLCHAIN_FILE=${IOS_CMAKE}/ios.toolchain.cmake \
+  -DPLATFORM=SIMULATOR \
+  -DBUCK2="${BUCK2:-$(which buck2)}" \
+  -DFLATC_EXECUTABLE="${FLATC:-$(which flatc)}" \
+  -DPYTHON_EXECUTABLE="${PYTHON:-$(which python3)}" \
+  ..
+
+# Move to the executorch folder and build
+cd .. && cmake --build cmake-ios-out -j9
 
 # Create an include folder in cmake-ios-out to include all header files
-mkdir include
-cp -r ../runtime include
-cp -r ../extension include
-cp -r ../utils include
+(cd cmake-ios-out && mkdir include && cd include && \
+ ln -s ../../runtime ../../util ../../extension .)
 ```
 
 

install_requirements.sh

@@ -36,3 +36,6 @@ pip install --pre transformers==${TRANSFORMERS_VERSION}
 
 TORCHSR_VERSION=1.0.4
 pip install --pre torchsr==${TORCHSR_VERSION}
+
+# Install flatc dependency
+bash build/install_flatc.sh