[BACKEND] Improved error messages when script resolution does not work (#846)

src/ytdl_sub/config/overrides.py

@@ -11,7 +11,9 @@ from ytdl_sub.entries.variables.override_variables import SUBSCRIPTION_NAME
 from ytdl_sub.entries.variables.override_variables import OverrideVariables
 from ytdl_sub.script.parser import parse
 from ytdl_sub.script.script import Script
+from ytdl_sub.script.utils.exceptions import ScriptVariableNotResolved
 from ytdl_sub.utils.exceptions import InvalidVariableNameException
+from ytdl_sub.utils.exceptions import StringFormattingException
 from ytdl_sub.utils.exceptions import ValidationException
 from ytdl_sub.utils.script import ScriptUtils
 from ytdl_sub.utils.scriptable import Scriptable
@@ -170,6 +172,11 @@ class Overrides(DictFormatterValidator, Scriptable):
         Returns
         -------
         The format_string after .format has been called
+
+        Raises
+        ------
+        StringFormattingException
+            If the formatter that is trying to be resolved cannot
         """
         script: Script = self.script
         unresolvable: Set[str] = self.unresolvable
@@ -177,11 +184,19 @@ class Overrides(DictFormatterValidator, Scriptable):
             script = entry.script
             unresolvable = entry.unresolvable
 
-        return formatter.post_process(
-            str(
-                script.resolve_once(
-                    dict({"tmp_var": formatter.format_string}, **(function_overrides or {})),
-                    unresolvable=unresolvable,
-                )["tmp_var"]
+        try:
+            return formatter.post_process(
+                str(
+                    script.resolve_once(
+                        dict({"tmp_var": formatter.format_string}, **(function_overrides or {})),
+                        unresolvable=unresolvable,
+                    )["tmp_var"]
+                )
             )
-        )
+        except ScriptVariableNotResolved as exc:
+            raise StringFormattingException(
+                "Tried to resolve the following script, but could not due to unresolved "
+                f"variables:\n {formatter.format_string}\n"
+                "This is most likely due to circular dependencies in variables. "
+                "If you think otherwise, please file a bug on GitHub and post your config. Thanks!"
+            ) from exc

src/ytdl_sub/script/script.py

@@ -16,6 +16,7 @@ from ytdl_sub.script.utils.exceptions import CycleDetected
 from ytdl_sub.script.utils.exceptions import IncompatibleFunctionArguments
 from ytdl_sub.script.utils.exceptions import InvalidCustomFunctionArguments
 from ytdl_sub.script.utils.exceptions import RuntimeException
+from ytdl_sub.script.utils.exceptions import ScriptVariableNotResolved
 from ytdl_sub.script.utils.name_validation import validate_variable_name
 from ytdl_sub.script.utils.type_checking import FunctionSpec
 
@@ -269,6 +270,11 @@ class Script:
         Returns
         -------
         Dict of resolved values
+
+        Raises
+        ------
+        ScriptVariableNotResolved
+            If specifying a filter of variable to resolve, and one of them does not.
         """
         resolved: Dict[Variable, Resolvable] = {
             Variable(name): value for name, value in (pre_resolved or {}).items()
@@ -322,7 +328,7 @@ class Script:
         if output_filter:
             for name in output_filter:
                 if name not in resolved_variables:
-                    raise ValueError(f"Specified {name} to resolve, but it did not")
+                    raise ScriptVariableNotResolved(f"Specified {name} to resolve, but it did not")
 
             return ScriptOutput(
                 {

src/ytdl_sub/utils/scriptable.py

@@ -9,6 +9,8 @@ from ytdl_sub.entries.script.variable_definitions import Variable
 from ytdl_sub.entries.script.variable_scripts import UNRESOLVED_VARIABLES
 from ytdl_sub.entries.script.variable_scripts import VARIABLE_SCRIPTS
 from ytdl_sub.script.script import Script
+from ytdl_sub.script.utils.exceptions import RuntimeException
+from ytdl_sub.utils.exceptions import StringFormattingException
 from ytdl_sub.utils.script import ScriptUtils
 
 
@@ -37,15 +39,28 @@ class Scriptable(ABC):
         Add new values to the script
         """
         values_as_str: Dict[str, str] = {
-            (key.variable_name if isinstance(key, Variable) else key): val
-            for key, val in values.items()
+            (var.variable_name if isinstance(var, Variable) else var): definition
+            for var, definition in values.items()
         }
 
         self.unresolvable -= set(list(values_as_str.keys()))
         self.script.add(
             ScriptUtils.add_sanitized_variables(
-                {name: ScriptUtils.to_script(value) for name, value in values_as_str.items()}
+                {
+                    name: ScriptUtils.to_script(definition)
+                    for name, definition in values_as_str.items()
+                }
             ),
             unresolvable=self.unresolvable,
         )
         self.update_script()
+
+        for name, definition in values_as_str.items():
+            try:
+                _ = self.script.get(variable_name=name)
+            except RuntimeException as exc:
+                raise StringFormattingException(
+                    f"Tried to create the variable with name {name} and definition:\n"
+                    f"{definition}\n"
+                    f"But could not because it has variable dependencies that are not resolved yet"
+                ) from exc