[roottest] Use nbconvert as a library in nbdiff.py

Using nbconvert as a Python library is less fragile, because otherwise
there is ambiguity how the command line util should be called (the name
changed over the versions as it migrated from ipython to jupyter).

Author: guitargeek

roottest/python/JupyROOT/nbdiff.py

@@ -2,22 +2,10 @@
 import json
 import os
 import shutil
-import subprocess
 import sys
 import tempfile
 
 nbExtension = ".ipynb"
-convCmdTmpl = (
-    "%s nbconvert "
-    "--to notebook "
-    "--ExecutePreprocessor.kernel_name=%s "
-    "--ExecutePreprocessor.enabled=True "
-    "--ExecutePreprocessor.timeout=3600 "
-    "--ExecutePreprocessor.startup_timeout=180 "
-    "%s "
-    "--output %s"
-)
-pythonInterpName = "python3"
 
 rootKernelFileContent = (
     """{
@@ -32,7 +20,7 @@
  ]
 }
 """
-    % pythonInterpName
+    % sys.executable
 )
 
 
@@ -149,34 +137,49 @@ def addEtcToEnvironment(inNBDirName):
     return ipythondir
 
 
-def getInterpreterName():
-    """Find if the 'jupyter' executable is available on the platform. If
-    yes, return its name else return 'ipython'
-    """
-    ret = subprocess.call("type jupyter", shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    return "jupyter" if ret == 0 else "i%s" % pythonInterpName
-
-
 def getKernelName(inNBName):
     with open(inNBName) as f:
         nbj = json.load(f)
     if nbj["metadata"]["kernelspec"]["language"] == "python":
-        return pythonInterpName
+        return "python3"
     else:  # we support only Python and C++
         return "root"
 
 
-def canReproduceNotebook(inNBName, kernelName, needsCompare):
+def canReproduceNotebook(inNBName, needsCompare):
+    from nbconvert import NotebookExporter
+    from nbconvert.preprocessors import ExecutePreprocessor
+    import nbformat
+
     tmpDir = addEtcToEnvironment(os.path.dirname(inNBName))
     outNBName = inNBName.replace(nbExtension, "_out" + nbExtension)
-    interpName = getInterpreterName()
-    convCmd = convCmdTmpl % (interpName, kernelName, inNBName, outNBName)
-    exitStatus = os.system(convCmd)  # we use system to inherit the environment in os.environ
-    shutil.rmtree(tmpDir)
+
+    # Load input notebook
+    with open(inNBName, "r", encoding="utf-8") as f:
+        nb = nbformat.read(f, as_version=4)
+
+    # Configure execution
+    ep = ExecutePreprocessor(
+        kernel_name=getKernelName(inNBName),
+        timeout=3600,
+        startup_timeout=180,
+        allow_errors=False,
+    )
+
+    # Run the notebook
+    ep.preprocess(nb, {"metadata": {"path": os.path.dirname(inNBName)}})
+
+    # Export executed notebook
+    with open(outNBName, "w", encoding="utf-8") as f:
+        nbformat.write(nb, f)
+
+    # Compare or return success
     if needsCompare:
         return compareNotebooks(inNBName, outNBName)
     else:
-        return exitStatus
+        return 0  # success
+
+    shutil.rmtree(tmpDir)
 
 
 def isInputNotebookFileName(filename):
@@ -206,7 +209,5 @@ def isInputNotebookFileName(filename):
     except:
         raise ImportError("Cannot import jupyter")
 
-    kernelName = getKernelName(nbFileName)
-
-    retCode = canReproduceNotebook(nbFileName, kernelName, needsCompare)
+    retCode = canReproduceNotebook(nbFileName, needsCompare)
     sys.exit(retCode)