add wrapper that thros RuntimeError if not importable for pycups

src/escpos/printer/__init__.py

@@ -2,7 +2,7 @@
 """printer implementations."""
 
 # from .win32raw import Win32Raw
-# from .cups import CupsPrinter
+from .cups import CupsPrinter
 from .dummy import Dummy
 from .file import File
 from .lp import LP
@@ -17,7 +17,7 @@ __all__ = [
     "Serial",
     "LP",
     "Dummy",
-    # "CupsPrinter",
+    "CupsPrinter",
     # "Win32Raw",
 ]
 

src/escpos/printer/cups.py

@@ -8,132 +8,156 @@
 :license: MIT
 """
 
+import functools
+import tempfile
+
 from ..escpos import Escpos
 
-_CUPSPRINT = False
+#: keeps track if the pycups dependency could be loaded (:py:class:`escpos.printer.CupsPrinter`)
-try:
+_DEP_PYCUPS = False
-    import tempfile
 
+try:
     import cups
 
-    _CUPSPRINT = True
+    _DEP_PYCUPS = True
 except ImportError:
     pass
 
-if _CUPSPRINT:
 
-    class CupsPrinter(Escpos):
+# TODO: dev build mode that let's the wrapper bypass?
-        """Simple CUPS printer connector.
 
-        .. note::
 
-            Requires ``pycups`` which in turn needs the cups development library package:
+def dependency_pycups(func):
-                - Ubuntu/Debian: ``libcups2-dev``
+    """Indicate dependency on pycups."""
-                - OpenSuse/Fedora: ``cups-devel``
 
-        inheritance:
+    @functools.wraps(func)
-
+    def wrapper(*args, **kwargs):
-        .. inheritance-diagram:: escpos.printer.CupsPrinter
+        """Throw a RuntimeError if pycups is not imported."""
-            :parts: 1
+        if not _DEP_PYCUPS:
-
+            raise RuntimeError(
-        """
+                "Printing with PyCups requires the pycups library to"
-
+                "be installed. Please refer to the documentation on"
-        def __init__(self, printer_name=None, *args, **kwargs):
+                "what to install and install the dependencies for pycups."
-            """Class constructor for CupsPrinter.
-
-            :param printer_name: CUPS printer name (Optional)
-            :type printer_name: str
-            :param host: CUPS server host/ip (Optional)
-            :type host: str
-            :param port: CUPS server port (Optional)
-            :type port: int
-            """
-            Escpos.__init__(self, *args, **kwargs)
-            host, port = args or (
-                kwargs.get("host", cups.getServer()),
-                kwargs.get("port", cups.getPort()),
             )
-            cups.setServer(host)
+        return func(*args, **kwargs)
-            cups.setPort(port)
+
-            self.conn = cups.Connection()
+    return wrapper
-            self.tmpfile = None
+
-            self.printer_name = printer_name
+
-            self.job_name = ""
+class CupsPrinter(Escpos):
+    """Simple CUPS printer connector.
+
+    .. note::
+
+        Requires ``pycups`` which in turn needs the cups development library package:
+            - Ubuntu/Debian: ``libcups2-dev``
+            - OpenSuse/Fedora: ``cups-devel``
+
+    inheritance:
+
+    .. inheritance-diagram:: escpos.printer.CupsPrinter
+        :parts: 1
+
+    """
+
+    @dependency_pycups
+    def __init__(self, printer_name=None, *args, **kwargs):
+        """Class constructor for CupsPrinter.
+
+        :param printer_name: CUPS printer name (Optional)
+        :type printer_name: str
+        :param host: CUPS server host/ip (Optional)
+        :type host: str
+        :param port: CUPS server port (Optional)
+        :type port: int
+        """
+        Escpos.__init__(self, *args, **kwargs)
+        host, port = args or (
+            kwargs.get("host", cups.getServer()),
+            kwargs.get("port", cups.getPort()),
+        )
+        cups.setServer(host)
+        cups.setPort(port)
+        self.conn = cups.Connection()
+        self.tmpfile = None
+        self.printer_name = printer_name
+        self.job_name = ""
+        self.pending_job = False
+        self.open()
+
+    @property
+    def printers(self):
+        """Available CUPS printers."""
+        return self.conn.getPrinters()
+
+    def open(self, job_name="python-escpos"):
+        """Set up a new print job and target the printer.
+
+        A call to this method is required to send new jobs to
+        the same CUPS connection.
+
+        Defaults to default CUPS printer.
+        Creates a new temporary file buffer.
+        """
+        self.job_name = job_name
+        if self.printer_name not in self.printers:
+            self.printer_name = self.conn.getDefault()
+        self.tmpfile = tempfile.NamedTemporaryFile(delete=True)
+
+    def _raw(self, msg):
+        """Append any command sent in raw format to temporary file.
+
+        :param msg: arbitrary code to be printed
+        :type msg: bytes
+        """
+        self.pending_job = True
+        try:
+            self.tmpfile.write(msg)
+        except ValueError:
             self.pending_job = False
-            self.open()
+            raise ValueError("Printer job not opened")
 
-        @property
+    @dependency_pycups
-        def printers(self):
+    def send(self):
-            """Available CUPS printers."""
+        """Send the print job to the printer."""
-            return self.conn.getPrinters()
+        if self.pending_job:
+            # Rewind tempfile
+            self.tmpfile.seek(0)
+            # Print temporary file via CUPS printer.
+            self.conn.printFile(
+                self.printer_name,
+                self.tmpfile.name,
+                self.job_name,
+                {"document-format": cups.CUPS_FORMAT_RAW},
+            )
+        self._clear()
 
-        def open(self, job_name="python-escpos"):
+    def _clear(self):
-            """Set up a new print job and target the printer.
+        """Finish the print job.
 
-            A call to this method is required to send new jobs to
+        Remove temporary file.
-            the same CUPS connection.
+        """
+        self.tmpfile.close()
+        self.pending_job = False
 
-            Defaults to default CUPS printer.
+    def _read(self):
-            Creates a new temporary file buffer.
+        """Return a single-item array with the accepting state of the print queue.
-            """
-            self.job_name = job_name
-            if self.printer_name not in self.printers:
-                self.printer_name = self.conn.getDefault()
-            self.tmpfile = tempfile.NamedTemporaryFile(delete=True)
 
-        def _raw(self, msg):
+        states: idle = [3], printing a job = [4], stopped = [5]
-            """Append any command sent in raw format to temporary file.
+        """
+        printer = self.printers.get(self.printer_name, {})
+        state = printer.get("printer-state")
+        if not state:
+            return []
+        return [state]
 
-            :param msg: arbitrary code to be printed
+    def close(self):
-            :type msg: bytes
+        """Close CUPS connection.
-            """
-            self.pending_job = True
-            try:
-                self.tmpfile.write(msg)
-            except ValueError:
-                self.pending_job = False
-                raise ValueError("Printer job not opened")
 
-        def send(self):
+        Send pending job to the printer if needed.
-            """Send the print job to the printer."""
+        """
-            if self.pending_job:
+        if self.pending_job:
-                # Rewind tempfile
+            self.send()
-                self.tmpfile.seek(0)
+        if self.conn:
-                # Print temporary file via CUPS printer.
+            print("Closing CUPS connection to printer {}".format(self.printer_name))
-                self.conn.printFile(
+            self.conn = None
-                    self.printer_name,
-                    self.tmpfile.name,
-                    self.job_name,
-                    {"document-format": cups.CUPS_FORMAT_RAW},
-                )
-            self._clear()
-
-        def _clear(self):
-            """Finish the print job.
-
-            Remove temporary file.
-            """
-            self.tmpfile.close()
-            self.pending_job = False
-
-        def _read(self):
-            """Return a single-item array with the accepting state of the print queue.
-
-            states: idle = [3], printing a job = [4], stopped = [5]
-            """
-            printer = self.printers.get(self.printer_name, {})
-            state = printer.get("printer-state")
-            if not state:
-                return []
-            return [state]
-
-        def close(self):
-            """Close CUPS connection.
-
-            Send pending job to the printer if needed.
-            """
-            if self.pending_job:
-                self.send()
-            if self.conn:
-                print("Closing CUPS connection to printer {}".format(self.printer_name))
-                self.conn = None

tox.ini

@@ -22,7 +22,6 @@ deps = jaconv
        pytest-mock
        hypothesis>4
        python-barcode
-       pycups
 commands = pytest
 passenv = ESCPOS_CAPABILITIES_PICKLE_DIR, ESCPOS_CAPABILITIES_FILE, CI, TRAVIS, TRAVIS_*, APPVEYOR, APPVEYOR_*, CODECOV_*
 setenv = PY_IGNORE_IMPORTMISMATCH=1