Add typing for camelot/backends

Author: foarsitter

camelot/backends/base.py

@@ -0,0 +1,12 @@
+"""Classes and functions for the ImageConversionBackend backends."""
+
+
+class ConversionBackend:  # noqa D101
+
+    def installed(self) -> bool:  # noqa D102
+        raise NotImplementedError
+
+    def convert(  # noqa D102
+        self, pdf_path: str, png_path: str, resolution: int = 300
+    ) -> None:  # noqa D102
+        raise NotImplementedError

camelot/backends/ghostscript_backend.py

@@ -1,10 +1,12 @@
 """Creates a ghostscript backend class to convert a pdf to a png file."""
 
+from camelot.backends.base import ConversionBackend
 
-class GhostscriptBackend:
+
+class GhostscriptBackend(ConversionBackend):
     """Classmethod to create GhostscriptScriptBackend."""
 
-    def convert(self, pdf_path, png_path, resolution=300):
+    def convert(self, pdf_path: str, png_path: str, resolution: int = 300) -> None:
         """Convert a PDF to a PNG image using Ghostscript .
 
         Parameters
@@ -22,7 +24,7 @@ def convert(self, pdf_path, png_path, resolution=300):
             [description]
         """
         try:
-            import ghostscript
+            import ghostscript  # type: ignore[import-untyped]
         except RuntimeError:
             raise OSError(
                 "Ghostscript is not installed. You can install it using the instructions"

camelot/backends/image_conversion.py

@@ -1,38 +1,52 @@
-"""Classes tand functions for the ImageConversionBackend backends."""
+"""Classes and functions for the ImageConversionBackend backends."""
 
+from typing import Dict
+from typing import List
+from typing import Type
+
+from .base import ConversionBackend
 from .ghostscript_backend import GhostscriptBackend
 from .poppler_backend import PopplerBackend
 
 
-BACKENDS = {"poppler": PopplerBackend, "ghostscript": GhostscriptBackend}
+BACKENDS: Dict[str, Type[ConversionBackend]] = {
+    "poppler": PopplerBackend,
+    "ghostscript": GhostscriptBackend,
+}
+
+
+class ImageConversionError(ValueError):  # noqa D101
+    pass
 
 
 class ImageConversionBackend:
     """Classes the ImageConversionBackend backend."""
 
-    def __init__(self, backend="poppler", use_fallback=True):
+    def __init__(self, backend: str = "poppler", use_fallback: bool = True) -> None:
         """Initialize the conversion backend .
 
         Parameters
         ----------
         backend : str, optional
-            [description], by default "poppler"
+            Backend for image conversion, by default "poppler"
         use_fallback : bool, optional
-            [description], by default True
+            Fallback to another backend if unavailable, by default True
 
         Raises
         ------
         ValueError
-            [description]
+            Raise an error if the backend is not supported.
         """
         if backend not in BACKENDS.keys():
             raise ValueError(f"Image conversion backend {backend!r} not supported")
 
-        self.backend = backend
-        self.use_fallback = use_fallback
-        self.fallbacks = list(filter(lambda x: x != backend, BACKENDS.keys()))
+        self.backend: str = backend
+        self.use_fallback: bool = use_fallback
+        self.fallbacks: List[str] = list(
+            filter(lambda x: x != backend, BACKENDS.keys())
+        )
 
-    def convert(self, pdf_path, png_path):
+    def convert(self, pdf_path: str, png_path: str) -> None:
         """Convert PDF to png_path.
 
         Parameters
@@ -52,22 +66,17 @@ def convert(self, pdf_path, png_path):
         try:
             converter = BACKENDS[self.backend]()
             converter.convert(pdf_path, png_path)
-        except Exception as e:
-            import sys
-
+        except Exception as f:
             if self.use_fallback:
                 for fallback in self.fallbacks:
                     try:
                         converter = BACKENDS[fallback]()
                         converter.convert(pdf_path, png_path)
                     except Exception as e:
-                        raise type(e)(
-                            str(e) + f" with image conversion backend {fallback!r}"
-                        ).with_traceback(sys.exc_info()[2])
-                        continue
+                        msg = f"Image conversion failed with image conversion backend {fallback!r}"
+                        raise ImageConversionError(msg) from e
                     else:
                         break
             else:
-                raise type(e)(
-                    str(e) + f" with image conversion backend {self.backend!r}"
-                ).with_traceback(sys.exc_info()[2])
+                msg = f"Image conversion failed with image conversion backend {self.backend!r}"
+                raise ImageConversionError(msg) from f

camelot/backends/poppler_backend.py

@@ -13,14 +13,16 @@
 import subprocess
 import sys
 
+from camelot.backends.base import ConversionBackend
+
 
 path = os.path.dirname(sys.executable) + os.pathsep + os.environ["PATH"]
 
 
-class PopplerBackend:
+class PopplerBackend(ConversionBackend):
     """Classmethod to create a poplerBackendBackend class."""
 
-    def convert(self, pdf_path, png_path):
+    def convert(self, pdf_path: str, png_path: str, resolution: int = 300) -> None:
         """Convert PDF to png.
 
         Parameters
@@ -50,4 +52,4 @@ def convert(self, pdf_path, png_path):
                 " ".join(pdftopng_command), stderr=subprocess.STDOUT, shell=False
             )
         except subprocess.CalledProcessError as e:
-            raise ValueError(e.output)
+            raise ValueError(e.output) from e