[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

@@ -2,39 +2,9 @@
 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 = (
-    """{
- "language": "c++",
- "display_name": "ROOT C++",
- "argv": [
-  "%s",
-  "-m",
-  "JupyROOT.kernel.rootkernel",
-  "-f",
-  "{connection_file}"
- ]
-}
-"""
-    % pythonInterpName
-)
-
 
 # Replace the criterion according to which a line shall be skipped
 def customLineJunkFilter(line):
@@ -134,7 +104,21 @@ def createKernelSpec():
     rootKernelPath = os.path.join(kernelsPath, "root")
     os.mkdir(rootKernelPath)
     with open(os.path.join(rootKernelPath, "kernel.json"), "w") as kernel_file:
-        kernel_file.write(rootKernelFileContent)
+        kernel_file.write(
+            """{
+         "language": "c++",
+         "display_name": "ROOT C++",
+         "argv": [
+          "%s",
+          "-m",
+          "JupyROOT.kernel.rootkernel",
+          "-f",
+          "{connection_file}"
+         ]
+        }
+        """
+            % sys.executable
+        )
 
     return tmpd
 
@@ -149,39 +133,53 @@ 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):
+    import nbformat
+    from nbconvert.preprocessors import ExecutePreprocessor
+
     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)
+    outNBName = inNBName.replace(".ipynb", "_out.ipynb")
+
+    # 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):
     if not filename.endswith(".ipynb"):
-        print("Notebook files shall have the %s extension" % nbExtension)
+        print("Notebook files shall have the .ipynb extension")
         return False
     return True
 
@@ -200,13 +198,5 @@ def isInputNotebookFileName(filename):
     if not isInputNotebookFileName(nbFileName):
         sys.exit(1)
 
-    try:
-        # If jupyter is there, ipython is too
-        import jupyter
-    except:
-        raise ImportError("Cannot import jupyter")
-
-    kernelName = getKernelName(nbFileName)
-
-    retCode = canReproduceNotebook(nbFileName, kernelName, needsCompare)
+    retCode = canReproduceNotebook(nbFileName, needsCompare)
     sys.exit(retCode)