feat(tvix/eval): implement `builtins.hashFile` r/7625

The primary addition is the `builtin_hashFile` function which attempts
value-path coercion and on success reads the file to a nix_string.
Similar to the `builtins_hashString` implementation, the hash is then
derived using the `hash_nix_string` function in the introduced hash
module which has extracted hashing functionality initially specified in
cl/11005.

Change-Id: I5e3ef0317223af99488ebb79efc2fb49b4cbc1b6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11007
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

1 files changed, 12 insertions, 1 deletions

diff --git a/tvix/eval/src/builtins/impure.rs b/tvix/eval/src/builtins/impure.rs
index def6ce29094c..aad55c7331e8 100644
--- a/tvix/eval/src/builtins/impure.rs
+++ b/tvix/eval/src/builtins/impure.rs
@@ -21,7 +21,7 @@ mod impure_builtins {
     use std::os::unix::ffi::OsStrExt;
 
     use super::*;
-    use crate::builtins::coerce_value_to_path;
+    use crate::builtins::{coerce_value_to_path, hash::hash_nix_string};
 
     #[builtin("getEnv")]
     async fn builtin_get_env(co: GenCo, var: Value) -> Result<Value, ErrorKind> {
@@ -30,6 +30,17 @@ mod impure_builtins {
             .into())
     }
 
+    #[builtin("hashFile")]
+    #[allow(non_snake_case)]
+    async fn builtin_hashFile(co: GenCo, algo: Value, path: Value) -> Result<Value, ErrorKind> {
+        let path = match coerce_value_to_path(&co, path).await? {
+            Err(cek) => return Ok(Value::from(cek)),
+            Ok(p) => p,
+        };
+        let s = generators::request_read_to_string(&co, path).await;
+        hash_nix_string(algo.to_str()?, s.to_str()?).map(Value::from)
+    }
+
     #[builtin("pathExists")]
     async fn builtin_path_exists(co: GenCo, path: Value) -> Result<Value, ErrorKind> {
         match coerce_value_to_path(&co, path).await? {