Fix build-wasm on Windows

Cargo.lock

@@ -1,5 +1,7 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "aho-corasick"
 version = "0.7.15"
@@ -180,6 +182,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "either"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+
 [[package]]
 name = "form_urlencoded"
 version = "1.0.1"
@@ -664,6 +672,7 @@ dependencies = [
  "tree-sitter-tags",
  "walkdir",
  "webbrowser",
+ "which",
 ]
 
 [[package]]
@@ -835,6 +844,16 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "which"
+version = "4.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b55551e42cbdf2ce2bedd2203d0cc08dba002c27510f86dab6d0ce304cba3dfe"
+dependencies = [
+ "either",
+ "libc",
+]
+
 [[package]]
 name = "widestring"
 version = "0.4.3"

cli/Cargo.toml

@@ -38,6 +38,7 @@ smallbitvec = "2.3.0"
 tiny_http = "0.8"
 walkdir = "2.3"
 webbrowser = "0.5.1"
+which = "4.1.0"
 
 [dependencies.tree-sitter]
 version = ">= 0.17.0"

cli/src/wasm.rs

@@ -4,6 +4,7 @@ use std::ffi::{OsStr, OsString};
 use std::fs;
 use std::path::Path;
 use std::process::Command;
+use which::which;
 
 pub fn get_grammar_name(src_dir: &Path) -> Result<String> {
     let grammar_json_path = src_dir.join("grammar.json");
@@ -22,9 +23,23 @@ pub fn compile_language_to_wasm(language_dir: &Path, force_docker: bool) -> Resu
     let output_filename = format!("tree-sitter-{}.wasm", grammar_name);
 
     let mut command;
-    if !force_docker && Command::new("emcc").output().is_ok() {
-        command = Command::new("emcc");
-        command.current_dir(&language_dir);
+    if !force_docker {
+        let emcc_bin;
+        if cfg!(windows) {
+            emcc_bin = "emcc.bat"
+        } else {
+            emcc_bin = "emcc"
+        };
+        let emcc_which = which(emcc_bin).unwrap();
+        let emcc_path = emcc_which.to_str().unwrap();
+        if Command::new(emcc_path).output().is_ok() {
+            command = Command::new(emcc_path);
+            command.current_dir(&language_dir);
+        } else {
+            return Error::err(
+                "You must have either emcc or docker on your PATH to run this command".to_string(),
+            );
+        }
     } else if Command::new("docker").output().is_ok() {
         command = Command::new("docker");
         command.args(&["run", "--rm"]);