feat: string context

nix-js/tests/string_context.rs

@@ -288,3 +288,92 @@ fn interpolation_derivation_equals_tostring() {
     );
     assert_eq!(result, Value::Bool(true));
 }
+
+#[test]
+fn substring_preserves_context() {
+    let result = eval(
+        r#"
+        let
+          drv = derivation { name = "test"; builder = "/bin/sh"; system = "x86_64-linux"; };
+          str = builtins.toString drv;
+          sub = builtins.substring 0 10 str;
+        in builtins.hasContext sub
+        "#,
+    );
+    assert_eq!(result, Value::Bool(true));
+}
+
+#[test]
+fn substring_zero_length_preserves_context() {
+    let result = eval(
+        r#"
+        let
+          drv = derivation { name = "test"; builder = "/bin/sh"; system = "x86_64-linux"; };
+          str = builtins.toString drv;
+          empty = builtins.substring 0 0 str;
+        in builtins.hasContext empty
+        "#,
+    );
+    assert_eq!(result, Value::Bool(true));
+}
+
+#[test]
+fn substring_zero_length_empty_value() {
+    let result = eval(
+        r#"
+        let
+          drv = derivation { name = "test"; builder = "/bin/sh"; system = "x86_64-linux"; };
+          str = builtins.toString drv;
+          empty = builtins.substring 0 0 str;
+        in empty == ""
+        "#,
+    );
+    assert_eq!(result, Value::Bool(true));
+}
+
+#[test]
+fn concatStringsSep_preserves_context() {
+    let result = eval(
+        r#"
+        let
+          drv1 = derivation { name = "test1"; builder = "/bin/sh"; system = "x86_64-linux"; };
+          drv2 = derivation { name = "test2"; builder = "/bin/sh"; system = "x86_64-linux"; };
+          str1 = builtins.toString drv1;
+          str2 = builtins.toString drv2;
+          combined = builtins.concatStringsSep ":" [str1 str2];
+        in builtins.hasContext combined
+        "#,
+    );
+    assert_eq!(result, Value::Bool(true));
+}
+
+#[test]
+fn concatStringsSep_merges_contexts() {
+    let result = eval(
+        r#"
+        let
+          drv1 = derivation { name = "test1"; builder = "/bin/sh"; system = "x86_64-linux"; };
+          drv2 = derivation { name = "test2"; builder = "/bin/sh"; system = "x86_64-linux"; };
+          str1 = builtins.toString drv1;
+          str2 = builtins.toString drv2;
+          combined = builtins.concatStringsSep ":" [str1 str2];
+          ctx = builtins.getContext combined;
+        in builtins.length (builtins.attrNames ctx)
+        "#,
+    );
+    assert_eq!(result, Value::Int(2));
+}
+
+#[test]
+fn concatStringsSep_separator_has_context() {
+    let result = eval(
+        r#"
+        let
+          drv = derivation { name = "test"; builder = "/bin/sh"; system = "x86_64-linux"; };
+          sep = builtins.toString drv;
+          combined = builtins.concatStringsSep sep ["a" "b"];
+        in builtins.hasContext combined
+        "#,
+    );
+    assert_eq!(result, Value::Bool(true));
+}