Start work on a WASM binding

cli/src/generate/mod.rs

@@ -15,7 +15,7 @@ mod grammars;
 mod nfa;
 mod node_types;
 mod npm_files;
-mod parse_grammar;
+pub mod parse_grammar;
 mod prepare_grammar;
 mod render;
 mod rules;

cli/src/generate/parse_grammar.rs

@@ -64,8 +64,8 @@ enum RuleJSON {
 }
 
 #[derive(Deserialize)]
-struct GrammarJSON {
-    name: String,
+pub(crate) struct GrammarJSON {
+    pub(crate) name: String,
     rules: Map<String, Value>,
     conflicts: Option<Vec<Vec<String>>>,
     externals: Option<Vec<RuleJSON>>,

cli/src/lib.rs

@@ -8,6 +8,7 @@ pub mod parse;
 pub mod properties;
 pub mod test;
 pub mod util;
+pub mod wasm;
 
 #[cfg(test)]
 mod tests;

cli/src/main.rs

@@ -5,7 +5,7 @@ use std::path::Path;
 use std::process::exit;
 use std::{u64, usize};
 use tree_sitter_cli::{
-    config, error, generate, highlight, loader, logger, parse, properties, test,
+    config, error, generate, highlight, loader, logger, parse, properties, test, wasm,
 };
 
 fn main() {
@@ -90,6 +90,11 @@ fn run() -> error::Result<()> {
                 .arg(Arg::with_name("html").long("html").short("h"))
                 .arg(Arg::with_name("time").long("time").short("t")),
         )
+        .subcommand(
+            SubCommand::with_name("build-wasm")
+                .about("Compile a parser to WASM")
+                .arg(Arg::with_name("path").index(1).multiple(true)),
+        )
         .get_matches();
 
     let home_dir = dirs::home_dir().expect("Failed to read home directory");
@@ -237,6 +242,9 @@ fn run() -> error::Result<()> {
                 )));
             }
         }
+    } else if let Some(matches) = matches.subcommand_matches("build-wasm") {
+        let grammar_path = current_dir.join(matches.value_of("path").unwrap_or(""));
+        wasm::compile_language_to_wasm(&grammar_path)?;
     }
 
     Ok(())

cli/src/wasm.rs

@@ -0,0 +1,72 @@
+use super::error::{Error, Result};
+use super::generate::parse_grammar::GrammarJSON;
+use std::fs;
+use std::path::Path;
+use std::process::Command;
+
+pub fn compile_language_to_wasm(language_dir: &Path) -> Result<()> {
+    let src_dir = language_dir.join("src");
+    let grammar_json_path = src_dir.join("grammar.json");
+    let grammar_json = fs::read_to_string(&grammar_json_path).map_err(|e| {
+        format!(
+            "Failed to read grammar file {:?} - {}",
+            grammar_json_path, e
+        )
+    })?;
+    let grammar: GrammarJSON = serde_json::from_str(&grammar_json).map_err(|e| {
+        format!(
+            "Failed to parse grammar file {:?} - {}",
+            grammar_json_path, e
+        )
+    })?;
+
+    let mut command = Command::new("emcc");
+    command.args(&[
+        "-o",
+        &format!("tree-sitter-{}.wasm", grammar.name),
+        "-Os",
+        "-s",
+        "WASM=1",
+        "-s",
+        "SIDE_MODULE=1",
+        "-s",
+        &format!("EXPORTED_FUNCTIONS=[\"_tree_sitter_{}\"]", grammar.name),
+    ]);
+    command.arg("-I").arg(&src_dir);
+
+    // Find source files to compile
+    let entries = fs::read_dir(&src_dir)
+        .map_err(|e| format!("Failed to read source directory {:?} - {}", src_dir, e))?;
+
+    for entry in entries {
+        let entry = entry?;
+        let file_name = entry.file_name();
+
+        // Do not compile the node.js binding file.
+        if file_name
+            .to_str()
+            .map_or(false, |s| s.starts_with("binding"))
+        {
+            continue;
+        }
+
+        // Compile any .c, .cc, or .cpp files
+        if let Some(extension) = Path::new(&file_name).extension().and_then(|s| s.to_str()) {
+            if extension == "c" || extension == "cc" || extension == "cpp" {
+                command.arg(entry.path());
+            }
+        }
+    }
+
+    let output = command
+        .output()
+        .map_err(|e| format!("Failed to run emcc command - {}", e))?;
+    if output.status.success() {
+        Ok(())
+    } else {
+        Err(Error::from(format!(
+            "emcc command failed - {}",
+            String::from_utf8_lossy(&output.stderr)
+        )))
+    }
+}