1 files changed, 92 insertions, 0 deletions
diff --git a/tvix/eval/src/builtins/impure.rs b/tvix/eval/src/builtins/impure.rs
new file mode 100644
index 000000000000..5324fd565304
--- /dev/null
+++ b/tvix/eval/src/builtins/impure.rs
@@ -0,0 +1,92 @@
+use builtin_macros::builtins;
+use genawaiter::rc::Gen;
+
+use std::{
+    env,
+    time::{SystemTime, UNIX_EPOCH},
+};
+
+use crate::{
+    self as tvix_eval,
+    errors::ErrorKind,
+    io::FileType,
+    value::NixAttrs,
+    vm::generators::{self, GenCo},
+    NixString, Value,
+};
+
+#[builtins]
+mod impure_builtins {
+    use super::*;
+    use crate::builtins::coerce_value_to_path;
+
+    #[builtin("getEnv")]
+    async fn builtin_get_env(co: GenCo, var: Value) -> Result<Value, ErrorKind> {
+        Ok(env::var(var.to_str()?).unwrap_or_else(|_| "".into()).into())
+    }
+
+    #[builtin("pathExists")]
+    async fn builtin_path_exists(co: GenCo, path: Value) -> Result<Value, ErrorKind> {
+        match coerce_value_to_path(&co, path).await? {
+            Err(cek) => Ok(Value::Catchable(cek)),
+            Ok(path) => Ok(generators::request_path_exists(&co, path).await),
+        }
+    }
+
+    #[builtin("readDir")]
+    async fn builtin_read_dir(co: GenCo, path: Value) -> Result<Value, ErrorKind> {
+        match coerce_value_to_path(&co, path).await? {
+            Err(cek) => Ok(Value::Catchable(cek)),
+            Ok(path) => {
+                let dir = generators::request_read_dir(&co, path).await;
+                let res = dir.into_iter().map(|(name, ftype)| {
+                    (
+                        // TODO: propagate Vec<u8> or bytes::Bytes into NixString.
+                        NixString::from(
+                            String::from_utf8(name.to_vec()).expect("parsing file name as string"),
+                        ),
+                        Value::String(
+                            match ftype {
+                                FileType::Directory => "directory",
+                                FileType::Regular => "regular",
+                                FileType::Symlink => "symlink",
+                                FileType::Unknown => "unknown",
+                            }
+                            .into(),
+                        ),
+                    )
+                });
+
+                Ok(Value::attrs(NixAttrs::from_iter(res)))
+            }
+        }
+    }
+
+    #[builtin("readFile")]
+    async fn builtin_read_file(co: GenCo, path: Value) -> Result<Value, ErrorKind> {
+        match coerce_value_to_path(&co, path).await? {
+            Err(cek) => Ok(Value::Catchable(cek)),
+            Ok(path) => Ok(generators::request_read_to_string(&co, path).await),
+        }
+    }
+}
+
+/// Return all impure builtins, that is all builtins which may perform I/O
+/// outside of the VM and so cannot be used in all contexts (e.g. WASM).
+pub fn impure_builtins() -> Vec<(&'static str, Value)> {
+    let mut result = impure_builtins::builtins();
+
+    // currentTime pins the time at which evaluation was started
+    {
+        let seconds = match SystemTime::now().duration_since(UNIX_EPOCH) {
+            Ok(dur) => dur.as_secs() as i64,
+
+            // This case is hit if the system time is *before* epoch.
+            Err(err) => -(err.duration().as_secs() as i64),
+        };
+
+        result.push(("currentTime", Value::Integer(seconds)));
+    }
+
+    result
+}