ghostscript: Refactor checking for executable name on Windows

src/ocrmypdf/exec/ghostscript.py

@@ -27,6 +27,7 @@ from io import BytesIO
 from os import fspath
 from pathlib import Path
 from subprocess import PIPE, run, CalledProcessError
+from shutil import which
 
 from PIL import Image
 
@@ -37,12 +38,11 @@ gslog = logging.getLogger()
 
 GS = 'gs'
 if os.name == 'nt':
-    GS = 'gswin64c'
-    try:
-        get_version(GS)
-    except MissingDependencyError:
-        GS = 'gswin32c'
-        get_version(GS)
+    GS = which('gswin64c')
+    if not GS:
+        GS = which('gswin32c')
+        if not GS:
+            raise MissingDependencyError("Ghostscript (gswin64c or gswin32c)")
 
 
 @lru_cache(maxsize=1)

tests/spoof/gs.py

@@ -0,0 +1,40 @@
+# © 2019 James R. Barlow: github.com/jbarlow83
+#
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+"""Find Ghostscript executable"""
+
+
+import os
+import shutil
+
+
+def real_ghostscript(argv):
+    if os.name != 'nt':
+        gs = shutil.which('gs')
+        gs_args = [gs] + argv[1:]
+        os.execv(gs_args[0], gs_args)
+    else:
+        gs = shutil.which('gswin64c')
+        if not gs:
+            gs = shutil.which('gswin32c')
+        os.execv(gs, argv[1:])
+
+    return  # Not reachable

tests/spoof/gs_feature_elision.py

@@ -30,10 +30,7 @@ from subprocess import check_call
 PDF/A creation."""
 
 
-def real_ghostscript(argv):
-    gs_args = ['gs'] + argv[1:]
-    os.execvp("gs", gs_args)
-    return  # Not reachable
+from gs import real_ghostscript
 
 
 elision_warning = """GPL Ghostscript 9.20: Setting Overprint Mode to 1

tests/spoof/gs_pdfa_failure.py

@@ -27,11 +27,7 @@ import sys
 """Replicate Ghostscript PDF/A conversion failure by suppressing some
 arguments"""
 
-
-def real_ghostscript(argv):
-    gs_args = ['gs'] + argv[1:]
-    os.execvp("gs", gs_args)
-    return  # Not reachable
+from gs import real_ghostscript
 
 
 def main():

tests/spoof/gs_raster_failure.py

@@ -27,10 +27,7 @@ import sys
 """Replicate Ghostscript raster failure while allowing rendering"""
 
 
-def real_ghostscript(argv):
-    gs_args = ['gs'] + argv[1:]
-    os.execvp("gs", gs_args)
-    return  # Not reachable
+from gs import real_ghostscript
 
 
 def main():

tests/spoof/gs_render_failure.py

@@ -26,10 +26,7 @@ import os
 import sys
 
 
-def real_ghostscript(argv):
-    gs_args = ['gs'] + argv[1:]
-    os.execvp("gs", gs_args)
-    return  # Not reachable
+from gs import real_ghostscript
 
 
 def main():