Allow building the wasm libs with native emscripten instead of docker

And build them on the mac CI as well as the linux CI

script/build-wasm

@@ -1,12 +1,10 @@
 #!/usr/bin/env bash
 
-set -e
-
-if [[ "$1" == "--help" || "$1" == "-h" ]]; then
+usage() {
   cat <<EOF
 USAGE
 
-  $0 [--debug]
+  $0 [--help] [--debug] [--docker]
 
 SUMMARY
 
@@ -15,57 +13,97 @@ SUMMARY
 
 REQUIREMENTS
 
-  You must have the \`docker\` command on your PATH for this to work.
+  You must have either the \`emcc\` command or the \`docker\` command
+  on your PATH for this to work.
 
 OPTIONS
 
-  --debug: Compile the library more quickly, with fewer optimizations and more runtime assertions.
+  --help:   Display this message.
+  --debug:  Compile the library more quickly, with fewer optimizations
+            and more runtime assertions.
+  --docker: Run emscripten using docker, even if \`emcc\` is installed.
+            By default, \`emcc\` will be run directly when available.
 
 EOF
-  exit 0
-fi
+}
+
+set -e
 
 web_dir=lib/binding_web
 exports=$(cat ${web_dir}/exports.json)
-args="-Os"
-minify=1
+emscripten_flags="-Os"
+minify_js=1
+force_docker=0
 
-if [[ "$1" == "--debug" ]]; then
-  minify=0
-  args="-s ASSERTIONS=1 -s SAFE_HEAP=1 -Os"
+while [[ $# > 0 ]]; do
+  case "$1" in
+    --debug)
+      minify_js=0
+      emscripten_flags="-s ASSERTIONS=1 -s SAFE_HEAP=1 -Os"
+      ;;
+
+    --help)
+      usage
+      exit 0
+      ;;
+
+    --docker)
+      force_docker=1
+      ;;
+
+    *)
+      usage
+      echo "Unrecognized argument '$1'"
+      exit 1
+      ;;
+  esac
+  shift
+done
+
+emcc=
+if which emcc > /dev/null && [[ "$force_docker" == "0" ]]; then
+  export EMCC_FORCE_STDLIBS=libc++
+  emcc=emcc
+elif which docker > /dev/null; then
+  emcc="docker run               \
+    --rm                         \
+    -v $(pwd):/src               \
+    -u $(id -u)                  \
+    -e EMCC_FORCE_STDLIBS=libc++ \
+    trzeci/emscripten-slim       \
+    emcc"
+else
+  echo 'You must have either `docker` or `emcc` on your PATH to run this script'
+  exit 1
 fi
 
 mkdir -p target/scratch
 
-docker run                          \
-  --rm                              \
-  -v $(pwd):/src                    \
-  -u $(id -u)                       \
-  -e EMCC_FORCE_STDLIBS=libc++      \
-  trzeci/emscripten-slim            \
-                                    \
-  emcc                              \
-  -s WASM=1                         \
-  -s TOTAL_MEMORY=33554432          \
-  -s ALLOW_MEMORY_GROWTH            \
-  -s MAIN_MODULE=2                  \
-  -s NO_FILESYSTEM=1                \
+# Use emscripten to generate `tree-sitter.js` and `tree-sitter.wasm`
+# in the `target/scratch` directory
+$emcc                                \
+  -s WASM=1                          \
+  -s TOTAL_MEMORY=33554432           \
+  -s ALLOW_MEMORY_GROWTH             \
+  -s MAIN_MODULE=2                   \
+  -s NO_FILESYSTEM=1                 \
   -s "EXPORTED_FUNCTIONS=${exports}" \
-  $args                             \
-  -std=c99                          \
-  -D 'fprintf(...)='                \
-  -I lib/src                        \
-  -I lib/include                    \
-  -I lib/utf8proc                   \
-  --js-library ${web_dir}/imports.js   \
-  --pre-js ${web_dir}/prefix.js        \
-  --post-js ${web_dir}/binding.js      \
-  lib/src/lib.c                     \
-  ${web_dir}/binding.c                 \
+  $emscripten_flags                  \
+  -std=c99                           \
+  -D 'fprintf(...)='                 \
+  -I lib/src                         \
+  -I lib/include                     \
+  -I lib/utf8proc                    \
+  --js-library ${web_dir}/imports.js \
+  --pre-js ${web_dir}/prefix.js      \
+  --post-js ${web_dir}/binding.js    \
+  lib/src/lib.c                      \
+  ${web_dir}/binding.c               \
   -o target/scratch/tree-sitter.js
 
-
-if [[ "$minify" == "1" ]]; then
+# Use terser to write a minified version of `tree-sitter.js` into
+# the `lib/binding_web` directory.
+if [[ "$minify_js" == "1" ]]; then
   if [ ! -d ${web_dir}/node_modules/terser ]; then
     (
       cd ${web_dir}

script/fetch-emscripten

@@ -0,0 +1,30 @@
+#!/bin/bash
+
+set -e
+
+mkdir -p target
+EMSDK_DIR="./target/emsdk"
+
+(
+  if [ ! -f "$EMSDK_DIR/emsdk" ]; then
+    echo 'Downloading emscripten SDK...'
+    git clone https://github.com/emscripten-core/emsdk.git $EMSDK_DIR
+  fi
+
+  cd $EMSDK_DIR
+
+  echo 'Updating emscripten SDK...'
+  git pull
+  ./emsdk list
+
+  echo 'Installing latest emscripten...'
+  ./emsdk install latest
+
+  echo 'Activating latest emscripten...'
+  ./emsdk activate latest
+) >&2
+
+(
+  source "$EMSDK_DIR/emsdk_env.sh" > /dev/null
+  declare -px
+)