Remove action enum, and add Latexify specific exceptions (#68)

* refactoring

* add _repr_html_

* font -> span

* add more description about exceptions

* Update src/latexify/exceptions.py

Co-authored-by: Shigeki Karita <6745326+ShigekiKarita@users.noreply.github.com>

Co-authored-by: Shigeki Karita <6745326+ShigekiKarita@users.noreply.github.com>

Author: Yusuke Oda

src/latexify/constants.py

@@ -14,17 +14,8 @@
 """Latexify module-level constants"""
 
 import ast
-from typing import NamedTuple
 
 
-class Actions(NamedTuple):
-    """A class which holds supported actions as constants"""
-
-    SET_BOUNDS = "set_bounds"
-
-
-actions = Actions()
-
 PREFIXES = ["math", "numpy", "np"]
 
 BUILTIN_CALLEES = {

src/latexify/exceptions.py

@@ -0,0 +1,36 @@
+"""Exceptions used in Latexify."""
+
+
+class LatexifyError(Exception):
+    """Base class of all Latexify exceptions.
+
+    Subclasses of this exception does not mean incorrect use of the library by the user,
+    but informs users that Latexify went into something wrong during compiling the given
+    functions.
+    These functions are usually captured by the frontend functions (e.g., `with_latex`)
+    to prevent destroying the entire program.
+    Errors caused by the wrong inputs should raise built-in exceptions.
+    """
+
+    ...
+
+
+class LatexifyNotSupportedError(LatexifyError):
+    """Some subtree in the AST is not supported by the current implementation.
+
+    This error is raised when the library discovered incompatible syntaxes due to lack
+    of the implementation. Possibly this error would be resolved in the future.
+    """
+
+    ...
+
+
+class LatexifySyntaxError(LatexifyError):
+    """Some subtree in the AST is not supported.
+
+    This error is raised when the library discovered syntaxes that are not possible to
+    be processed anymore. This error is essential, and wouldn't be resolved in the
+    future.
+    """
+
+    ...

src/latexify/frontend.py

@@ -10,7 +10,7 @@
 
 import dill
 
-from latexify import latexify_visitor
+from latexify import exceptions, latexify_visitor
 from latexify.transformers.identifier_replacer import IdentifierReplacer
 
 
@@ -40,6 +40,9 @@ def get_latex(
 
     Returns:
         Generatee LaTeX description.
+
+    Raises:
+        latexify.exceptions.LatexifyError: Something went wrong during conversion.
     """
     try:
         source = inspect.getsource(fn)
@@ -67,9 +70,18 @@ def get_latex(
 class LatexifiedFunction:
     """Function with latex representation."""
 
+    _fn: Callable[..., Any]
+    _latex: str | None
+    _error: str | None
+
     def __init__(self, fn, **kwargs):
         self._fn = fn
-        self._str = get_latex(fn, **kwargs)
+        try:
+            self._latex = get_latex(fn, **kwargs)
+            self._error = None
+        except exceptions.LatexifyError as e:
+            self._latex = None
+            self._error = f"{type(e).__name__}: {str(e)}"
 
     @property
     def __doc__(self):
@@ -91,11 +103,23 @@ def __call__(self, *args):
         return self._fn(*args)
 
     def __str__(self):
-        return self._str
+        return self._latex if self._latex is not None else self._error
+
+    def _repr_html_(self):
+        """IPython hook to display HTML visualization."""
+        return (
+            '<span style="color: red;">' + self._error + "</span>"
+            if self._error is not None
+            else None
+        )
 
     def _repr_latex_(self):
         """IPython hook to display LaTeX visualization."""
-        return r"$$ \displaystyle " + self._str + " $$"
+        return (
+            r"$$ \displaystyle " + self._latex + " $$"
+            if self._latex is not None
+            else self._error
+        )
 
 
 def with_latex(*args, **kwargs) -> Callable[[Callable[..., Any]], LatexifiedFunction]:

src/latexify/latexify_visitor.py

@@ -8,6 +8,7 @@
 from latexify import constants
 from latexify import math_symbols
 from latexify import node_visitor_base
+from latexify import exceptions
 
 
 class LatexifyVisitor(node_visitor_base.NodeVisitorBase):
@@ -45,8 +46,10 @@ def __init__(
 
         self.assign_var = {}
 
-    def generic_visit(self, node, action):
-        return str(node)
+    def generic_visit(self, node, action) -> str:
+        raise exceptions.LatexifyNotSupportedError(
+            f"Unsupported AST: {type(node).__name__}"
+        )
 
     def visit_Module(self, node, action):  # pylint: disable=invalid-name
         return self.visit(node.body[0], "multi_lines")
@@ -78,7 +81,7 @@ def visit_FunctionDef(self, node, action):  # pylint: disable=invalid-name
                 elif isinstance(el, ast.Return):
                     break
         if body_str == "":
-            raise ValueError("`return` missing")
+            raise exceptions.LatexifySyntaxError("`return` missing")
 
         return name_str, arg_strs, assign_vars, body_str
 
@@ -126,7 +129,7 @@ def visit_Call(self, node, action):  # pylint: disable=invalid-name
         def _decorated_lstr_and_arg(node, callee_str, lstr):
             """Decorates lstr and get its associated arguments"""
             if callee_str == "sum" and isinstance(node.args[0], ast.GeneratorExp):
-                generator_info = self.visit(node.args[0], constants.actions.SET_BOUNDS)
+                generator_info = self.visit(node.args[0], "set_bounds")
                 arg_str, comprehension = generator_info
                 var_comp, args_comp = comprehension
                 if len(args_comp) == 1:
@@ -293,14 +296,13 @@ def visit_If(self, node, action):  # pylint: disable=invalid-name
         return latex + r", & \mathrm{otherwise} \end{array} \right."
 
     def visit_GeneratorExp_set_bounds(self, node):  # pylint: disable=invalid-name
-        action = constants.actions.SET_BOUNDS
         output = self.visit(node.elt)
         comprehensions = [
-            self.visit(generator, action) for generator in node.generators
+            self.visit(generator, "set_bounds") for generator in node.generators
         ]
         if len(comprehensions) == 1:
             return output, comprehensions[0]
-        raise TypeError(
+        raise exceptions.LatexifyNotSupportedError(
             "visit_GeneratorExp_sum() supports a single for clause"
             "but {} were given".format(len(comprehensions))
         )
@@ -351,6 +353,6 @@ def visit_comprehension_set_bounds(self, node):  # pylint: disable=invalid-name
             args = [self.visit(arg) for arg in node.iter.args]
             if len(args) in (1, 2):
                 return var, args
-        raise TypeError(
+        raise exceptions.LatexifyNotSupportedError(
             "Comprehension for sum only supports range func " "with 1 or 2 args"
         )

src/latexify/latexify_visitor_test.py

@@ -1,11 +1,23 @@
 """Tests for latexify.latexify_visitor."""
 
 import ast
+from latexify import exceptions
 import pytest
 
 from latexify.latexify_visitor import LatexifyVisitor
 
 
+def test_generic_visit() -> None:
+    class UnknownNode(ast.AST):
+        pass
+
+    with pytest.raises(
+        exceptions.LatexifyNotSupportedError,
+        match=r"^Unsupported AST: UnknownNode$",
+    ):
+        LatexifyVisitor().visit(UnknownNode())
+
+
 @pytest.mark.parametrize(
     "code,latex",
     [