FIX: Restore the env variable functionality

src/build/compile_test.rs

@@ -13,6 +13,7 @@
 //  limitations under the License.
 
 use std::cell::RefCell;
+use std::collections::BTreeMap;
 
 use regex::Regex;
 
@@ -24,7 +25,9 @@ fn assert_build(input: &str) {
     let i_paths = Vec::new();
     let out_buffer: Vec<u8> = Vec::new();
     let err_buffer: Vec<u8> = Vec::new();
-    let env = RefCell::new(Environment::new(out_buffer, err_buffer));
+    let mut env_vars = BTreeMap::new();
+    env_vars.insert("FOO".to_owned(), "bar".to_owned());
+    let env = RefCell::new(Environment::new_with_vars(out_buffer, err_buffer, env_vars));
     let mut b = FileBuilder::new("<Eval>", &i_paths, &env);
     b.enable_validate_mode();
     b.eval_string(input).unwrap();
@@ -148,6 +151,47 @@ fn test_type_checks() {
     assert_build(include_str!("../../integration_tests/types_test.ucg"));
 }
 
+#[test]
+fn test_environment_variable_exists() {
+    assert_build("assert { ok = env.FOO == \"bar\", desc = \"env var $FOO is bar\"};");
+}
+// TODO(jwall): that shadowing the env variable is not allowed?
+
+#[test]
+fn test_env_as_field_name_works() {
+    assert_build(
+        "let tpl = { env = \"quux\" };
+assert {
+    ok = env.FOO == \"bar\",
+    desc = \"env var $FOO is bar\",
+};
+assert {
+    ok = tpl.env == \"quux\",
+    desc = \"tpl.env is quux\",
+};
+
+let tpl2 = { env = { bar = 2 } };
+assert {
+    ok = tpl2.env.bar == 2,
+    desc = \"tpl2.env.bar is 2\",
+};
+",
+    );
+}
+// TODO(jwall): tests for missing values.
+
+#[test]
+fn test_env_is_not_a_valid_binding() {
+    assert_build_failure(
+        "let env = 1;",
+        vec![
+            Regex::new("Cannot use binding env").unwrap(),
+            Regex::new("It is a reserved word").unwrap(),
+            Regex::new("at line: 1 column: 5").unwrap(),
+        ],
+    );
+}
+
 #[test]
 #[should_panic(expected = "UserDefined: I am a failure!")]
 fn test_declarative_failures_are_caused_by_msg() {

src/build/opcode/environment.rs

@@ -17,16 +17,16 @@ use std::io::{Read, Write};
 use std::path::{Path, PathBuf};
 use std::rc::Rc;
 
-use super::cache;
 use super::pointer::OpPointer;
 use super::Error;
-use super::Value;
-use crate::build::stdlib;
+use super::{cache, Primitive};
+use super::{Composite, Value};
 use crate::build::AssertCollector;
 use crate::build::Val;
 use crate::convert::{ConverterRegistry, ImporterRegistry};
 use crate::iter::OffsetStrIter;
 use crate::parse::parse;
+use crate::{ast::Position, build::stdlib};
 
 // Shared Environmental between VM's for runtime usage.
 pub struct Environment<Stdout, Stderr>
@@ -47,6 +47,7 @@ where
 
 impl<Stdout: Write + Clone, Stderr: Write + Clone> Environment<Stdout, Stderr> {
     pub fn new(out: Stdout, err: Stderr) -> Self {
+        // TODO(jwall): populate this with environment variables?
         Self::new_with_vars(out, err, BTreeMap::new())
     }
 
@@ -66,6 +67,16 @@ impl<Stdout: Write + Clone, Stderr: Write + Clone> Environment<Stdout, Stderr> {
         return me;
     }
 
+    pub fn get_env_vars_tuple(&self) -> Value {
+        let mut fields = Vec::new();
+        let mut positions = Vec::new();
+        for (key, val) in self.env_vars.iter() {
+            fields.push((key.clone(), Rc::new(Value::P(Primitive::Str(val.clone())))));
+            positions.push((Position::new(0, 0, 0), Position::new(0, 0, 0)));
+        }
+        Value::C(Composite::Tuple(fields, positions))
+    }
+
     pub fn get_cached_path_val(&self, path: &String) -> Option<Rc<Value>> {
         self.val_cache.get(path).cloned()
     }

src/build/opcode/vm.rs

@@ -144,7 +144,7 @@ impl VM {
                 Op::Val(p) => self.push(Rc::new(P(p.clone())), pos)?,
                 Op::Cast(t) => self.op_cast(t)?,
                 Op::Sym(s) => self.push(Rc::new(S(s.clone())), pos)?,
-                Op::DeRef(s) => self.op_deref(s.clone(), &pos)?,
+                Op::DeRef(s) => self.op_deref(s.clone(), env, &pos)?,
                 Op::Add => self.op_add(pos)?,
                 Op::Mod => self.op_mod(pos)?,
                 Op::Sub => self.op_sub(pos)?,
@@ -242,8 +242,17 @@ impl VM {
         Ok(())
     }
 
-    fn op_deref(&mut self, name: String, pos: &Position) -> Result<(), Error> {
-        let (val, _) = self.get_binding(&name, pos)?.clone();
+    fn op_deref<O, E>(
+        &mut self,
+        name: String,
+        env: &RefCell<Environment<O, E>>,
+        pos: &Position,
+    ) -> Result<(), Error>
+    where
+        O: std::io::Write + Clone,
+        E: std::io::Write + Clone,
+    {
+        let (val, _) = self.get_binding(&name, env, pos)?.clone();
         self.push(val, pos.clone())
     }
 
@@ -1078,9 +1087,29 @@ impl VM {
         Ok(())
     }
 
-    pub fn get_binding(&self, name: &str, pos: &Position) -> Result<(Rc<Value>, Position), Error> {
+    pub fn get_binding<O, E>(
+        &self,
+        name: &str,
+        env: &RefCell<Environment<O, E>>,
+        pos: &Position,
+    ) -> Result<(Rc<Value>, Position), Error>
+    where
+        O: std::io::Write + Clone,
+        E: std::io::Write + Clone,
+    {
+        // TODO(jwall): Handle environment variables here?
         let tpl = if name == "self" {
             self.self_stack.last().cloned()
+        } else if name == "env" {
+            let candidate = self.symbols.get(name);
+            if candidate.is_some() {
+                candidate
+            } else {
+                Some((
+                    Rc::new(env.borrow().get_env_vars_tuple()),
+                    Position::new(0, 0, 0),
+                ))
+            }
         } else {
             self.symbols.get(name)
         };

src/main.rs

@@ -426,7 +426,11 @@ fn env_help() {
     );
 }
 
-fn do_repl(import_paths: &Vec<PathBuf>, strict: bool) -> std::result::Result<(), Box<dyn Error>> {
+fn do_repl(
+    import_paths: &Vec<PathBuf>,
+    strict: bool,
+    env: &RefCell<Environment<StdoutWrapper, StderrWrapper>>,
+) -> std::result::Result<(), Box<dyn Error>> {
     let config = rustyline::Config::builder();
     let mut editor = rustyline::Editor::<()>::with_config(
         config
@@ -458,10 +462,6 @@ fn do_repl(import_paths: &Vec<PathBuf>, strict: bool) -> std::result::Result<(),
             }
         }
     }
-    let env = std::cell::RefCell::new(build::opcode::Environment::new(
-        StdoutWrapper::new(),
-        StderrWrapper::new(),
-    ));
     let mut builder = build::FileBuilder::new(std::env::current_dir()?, import_paths, &env);
     builder.set_strict(strict);
 
@@ -469,8 +469,12 @@ fn do_repl(import_paths: &Vec<PathBuf>, strict: bool) -> std::result::Result<(),
     Ok(())
 }
 
-fn repl(import_paths: &Vec<PathBuf>, strict: bool) {
-    if let Err(e) = do_repl(import_paths, strict) {
+fn repl(
+    import_paths: &Vec<PathBuf>,
+    strict: bool,
+    env: &RefCell<Environment<StdoutWrapper, StderrWrapper>>,
+) {
+    if let Err(e) = do_repl(import_paths, strict, env) {
         eprintln!("{}", e);
         process::exit(1);
     }
@@ -482,7 +486,15 @@ fn main() {
     // FIXME(jwall): Do we want these to be shared or not?
     let registry = ConverterRegistry::make_registry();
     let mut import_paths = Vec::new();
-    let env = RefCell::new(Environment::new(StdoutWrapper::new(), StderrWrapper::new()));
+    let mut env_vars = BTreeMap::new();
+    for (var, val) in std::env::vars() {
+        env_vars.insert(var, val);
+    }
+    let env = RefCell::new(Environment::new_with_vars(
+        StdoutWrapper::new(),
+        StderrWrapper::new(),
+        env_vars,
+    ));
     if let Some(mut p) = dirs::home_dir() {
         p.push(".ucg");
         // Attempt to create directory if it doesn't exist.
@@ -518,7 +530,7 @@ fn main() {
     } else if let Some(_) = app_matches.subcommand_matches("env") {
         env_help()
     } else if let Some(_) = app_matches.subcommand_matches("repl") {
-        repl(&import_paths, strict)
+        repl(&import_paths, strict, &env)
     } else if let Some(matches) = app_matches.subcommand_matches("fmt") {
         if let Err(e) = fmt_command(matches) {
             eprintln!("{}", e);

src/parse/mod.rs

@@ -805,11 +805,33 @@ make_fn!(
     )
 );
 
+/// Verify binding is not a reserved word.
+macro_rules! match_binding_name {
+    ($i:expr,) => {{
+        use abortable_parser::{Error, Result};
+        let mut _i = $i.clone();
+        match match_type!(_i, BAREWORD) {
+            Result::Complete(i, t) => {
+                if t.fragment == "env" {
+                    return Result::Abort(Error::new(
+                        format!("Cannot use binding {}. It is a reserved word.", t.fragment),
+                        Box::new($i.clone()),
+                    ));
+                }
+                Result::Complete(i, t)
+            }
+            Result::Incomplete(i) => Result::Incomplete(i),
+            Result::Fail(e) => Result::Fail(e),
+            Result::Abort(e) => Result::Abort(e),
+        }
+    }};
+}
+
 make_fn!(
     let_stmt_body<SliceIter<Token>, Statement>,
     do_each!(
         pos => pos,
-        name => wrap_err!(match_type!(BAREWORD), "Expected name for binding"),
+        name => wrap_err!(match_binding_name!(), "Expected name for binding"),
         _ => optional!(trace_parse!(shape_suffix)),
         _ => punct!("="),
         val => trace_parse!(wrap_err!(expression, "Expected Expression to bind")),