WASM binding (#114)

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

.github/workflows/publish-wasm.yml

@@ -0,0 +1,23 @@
+name: publish-wasm
+
+permissions:
+  pull-requests: write
+  contents: write
+
+on: workflow_dispatch
+
+jobs:
+  publish-wasm:
+    name: publish
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Install wasm-pack
+        run: curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
+      - name: Build
+        run: wasm-pack build --target nodejs -r
+      - name: Publish
+        run: # TODO

.github/workflows/rust.yml

@@ -37,3 +37,11 @@ jobs:
     - name: Run tests (OPA Conformance)
       run: >-
         cargo test -r --test opa -- $(tr '\n' ' ' < tests/opa.passing)
+
+    - name: Install wasm-pack
+      run: curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
+
+    - name: Run wasm binding tests
+      run: |
+        cd bindings/wasm
+        wasm-pack test --node -r

Cargo.toml

@@ -1,3 +1,4 @@
+workspace = { members = ["bindings/wasm"] }
 [package]
 name = "regorus"
 description = "A fast, lightweight Rego (OPA policy language) interpreter"

README.md

@@ -61,6 +61,12 @@ $ cargo build -r --example regorus --features "yaml" --no-default-features; stri
 Regorus passes the [OPA v0.60.0 test-suite](https://www.openpolicyagent.org/docs/latest/ir/#test-suite) barring a few
 builtins. See [OPA Conformance](#opa-conformance) below.
 
+## Bindings
+
+Regorus can be used from a variety of languages:
+
+- Javascript (nodejs): Via npm package `regorus-wasm`. This package is Regorus compiled into WASM.
+
 ## Getting Started
 
 [examples/regorus](https://github.com/microsoft/regorus/blob/main/examples/regorus.rs) is an example program that

bindings/wasm/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "regorus-wasm"
+version = "0.1.0"
+edition = "2021"
+repository = "https://github.com/microsoft/regorus/bindings/wasm"
+description = "WASM bindings for Regorus - a fast, lightweight Rego interpreter written in Rust"
+keywords = ["interpreter", "opa", "policy-as-code", "rego"]
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+regorus = { path  = "../.." }
+serde_json = "1.0.111"
+wasm-bindgen = "0.2.90"
+
+[dev-dependencies]
+wasm-bindgen-test = "0.3.40"

bindings/wasm/README.md

@@ -0,0 +1,28 @@
+# regorus-wasm
+
+**Regorus** is
+
+  - *Rego*-*Rus(t)*  - A fast, light-weight [Rego](https://www.openpolicyagent.org/docs/latest/policy-language/)
+   interpreter written in Rust.
+  - *Rigorous* - A rigorous enforcer of well-defined Rego semantics.
+
+See [Repository](https://github.com/microsoft/regorus).
+
+`regorus-wasm` is Regorus compiled into WASM.
+
+## Usage
+
+In nodejs,
+
+``javascript
+
+var regorus = require('regorus-wasm')
+
+// Create an engine.
+var engine = new regorus.Engine();
+
+// Add Rego policy.
+engine.add_policy()
+
+
+```

bindings/wasm/src/lib.rs

@@ -0,0 +1,138 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+/// WASM wrapper for [`regorus::Engine`]
+pub struct Engine {
+    engine: regorus::Engine,
+}
+
+fn error_to_jsvalue<E: std::fmt::Display>(e: E) -> JsValue {
+    JsValue::from_str(&format!("{e}"))
+}
+
+impl Default for Engine {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Clone for Engine {
+    /// Clone a [`Engine`]
+    ///
+    /// To avoid having to parse same policy again, the engine can be cloned
+    /// after policies and data have been added.
+    fn clone(&self) -> Self {
+        Self {
+            engine: self.engine.clone(),
+        }
+    }
+}
+
+#[wasm_bindgen]
+impl Engine {
+    #[wasm_bindgen(constructor)]
+    /// Construct a new Engine
+    ///
+    /// See https://docs.rs/regorus/latest/regorus/struct.Engine.html
+    pub fn new() -> Self {
+        Self {
+            engine: regorus::Engine::new(),
+        }
+    }
+
+    /// Add a policy
+    ///
+    /// The policy is parsed into AST.
+    /// See https://docs.rs/regorus/latest/regorus/struct.Engine.html#method.add_policy
+    ///
+    /// * `path`: A filename to be associated with the policy.
+    /// * `rego`: Rego policy.
+    pub fn add_policy(&mut self, path: String, rego: String) -> Result<(), JsValue> {
+        self.engine.add_policy(path, rego).map_err(error_to_jsvalue)
+    }
+
+    /// Add policy data.
+    ///
+    /// See https://docs.rs/regorus/latest/regorus/struct.Engine.html#method.add_data
+    /// * `data`: JSON encoded value to be used as policy data.
+    pub fn add_data_json(&mut self, data: String) -> Result<(), JsValue> {
+        let data = regorus::Value::from_json_str(&data).map_err(error_to_jsvalue)?;
+        self.engine.add_data(data).map_err(error_to_jsvalue)
+    }
+
+    /// Set input.
+    ///
+    /// See https://docs.rs/regorus/0.1.0-alpha.2/regorus/struct.Engine.html#method.set_input
+    /// * `input`: JSON encoded value to be used as input to query.
+    pub fn set_input_json(&mut self, input: String) -> Result<(), JsValue> {
+        let input = regorus::Value::from_json_str(&input).map_err(error_to_jsvalue)?;
+        self.engine.set_input(input);
+        Ok(())
+    }
+
+    /// Evaluate query.
+    ///
+    /// See https://docs.rs/regorus/0.1.0-alpha.2/regorus/struct.Engine.html#method.eval_query
+    /// * `query`: Rego expression to be evaluate.
+    pub fn eval_query(&mut self, query: String) -> Result<String, JsValue> {
+        let results = self
+            .engine
+            .eval_query(query, false)
+            .map_err(error_to_jsvalue)?;
+        serde_json::to_string_pretty(&results).map_err(error_to_jsvalue)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use wasm_bindgen::prelude::*;
+    use wasm_bindgen_test::wasm_bindgen_test;
+
+    #[wasm_bindgen_test]
+    pub fn basic() -> Result<(), JsValue> {
+        let mut engine = crate::Engine::new();
+
+        // Exercise all APIs.
+        engine.add_data_json(
+            r#"
+        {
+           "foo" : "bar"
+        }
+        "#
+            .to_string(),
+        )?;
+
+        engine.set_input_json(
+            r#"
+        {
+           "message" : "Hello"
+        }
+        "#
+            .to_string(),
+        )?;
+
+        engine.add_policy(
+            "hello.rego".to_string(),
+            r#"
+            package test
+            message = input.message"#
+                .to_string(),
+        )?;
+
+        let results = engine.eval_query("data".to_string())?;
+        let r = regorus::Value::from_json_str(&results).map_err(crate::error_to_jsvalue)?;
+
+        let v = &r["result"][0]["expressions"][0]["value"];
+
+        // Ensure that input and policy were evaluated.
+        assert_eq!(v["test"]["message"], regorus::Value::from("Hello"));
+
+        // Test that data was set.
+        assert_eq!(v["foo"], regorus::Value::from("bar"));
+
+        Ok(())
+    }
+}