otk: add file to variable substitution errors too

This commit adds file context for errors from variable substitution
too.

src/otk/transform.py

@@ -24,7 +24,7 @@
 from .constant import NAME_VERSION, PREFIX, PREFIX_DEFINE, PREFIX_INCLUDE, PREFIX_OP, PREFIX_TARGET
 from .context import Context, validate_var_name
 from .error import (
-    IncludeNotFoundError,
+    IncludeNotFoundError, OTKError,
     ParseError, ParseTypeError, ParseValueError, ParseDuplicatedYamlKeyError,
     TransformDirectiveTypeError, TransformDirectiveUnknownError,
 )
@@ -287,7 +287,11 @@ def substitute_vars(ctx: Context, state: State, data: str) -> Any:
     # return its value directly.
     if m := re.fullmatch(pattern, data):
         validate_var_name(m.group("name"))
-        return ctx.variable(m.group("name"))
+        try:
+            var = ctx.variable(m.group("name"))
+        except OTKError as exc:
+            raise exc.__class__(str(exc), state)
+        return var
 
     if matches := re.finditer(pattern, data):
         for m in matches:

src/otk/tree.py

@@ -20,7 +20,8 @@ def wrapper(*args, **kwargs):
             if not isinstance(args[2], kind):
                 # XXX: this needs state to give proper errors
                 raise TransformDirectiveTypeError(
-                    f"otk.define expects a {kind!r} as its argument but received a `{type(args[2])}`: `{args[2]!r}`")
+                    f"otk.define expects a {kind!r} as its argument but "
+                    f"received a `{type(args[2])}`: `{args[2]!r}`", args[1])
             return function(*args, **kwargs)
 
         return wrapper

test/test_substitute_vars.py

@@ -47,7 +47,7 @@ def test_sub_var_multiple():
 
 
 def test_sub_var_missing_var_in_context():
-    state = State("")
+    state = State("foo.yaml")
     context = CommonContext()
     # toplevel
     expected_err = r"could not resolve 'a' as 'a' is not defined"
@@ -60,7 +60,8 @@ def test_sub_var_missing_var_in_context():
         substitute_vars(context, state, "${a.b}")
     # no subtree
     context.define("a", "foo")
-    expected_err = r"tried to look up 'a.b', but the value of prefix 'a' is not a dictionary but <class 'str'>"
+    expected_err = r"foo.yaml: tried to look up 'a.b', but the value of " \
+        "prefix 'a' is not a dictionary but <class 'str'>"
     with pytest.raises(TransformVariableTypeError, match=expected_err):
         substitute_vars(context, state, "${a.b}")
 
@@ -127,12 +128,16 @@ def test_substitute_vars():
 
 
 def test_substitute_vars_unhappy():
-    state = State("")
+    state = State("foo.yaml")
     ctx = CommonContext()
     ctx.define("dict", {})
 
-    with pytest.raises(TransformDirectiveTypeError):
+    with pytest.raises(TransformDirectiveTypeError) as exc:
         substitute_vars(ctx, state, 1)
+    assert "foo.yaml: otk.define expects a <class 'str'> as its argument but received a `<class 'int'>" in str(
+        exc.value)
 
-    with pytest.raises(TransformDirectiveTypeError):
+    with pytest.raises(TransformDirectiveTypeError) as exc:
         substitute_vars(ctx, state, "a${dict}b")
+    assert "foo.yaml: string 'a${dict}b' resolves to an incorrect type, " \
+        "expected int, float, or str but got dict" in str(exc.value)