Merge pull request #5279 from jdfreder/checknode

nbconvert: Make sure node is atleast version 0.9.12

IPython/nbconvert/filters/markdown.py

@@ -18,18 +18,21 from __future__ import print_function
 # Stdlib imports
 import os
 import subprocess
+import warnings
 from io import TextIOWrapper, BytesIO
 
 # IPython imports
 from IPython.nbconvert.utils.pandoc import pandoc
 from IPython.nbconvert.utils.exceptions import ConversionException
-from IPython.utils.process import find_cmd, FindCmdError
+from IPython.utils.process import get_output_error_code
 from IPython.utils.py3compat import cast_bytes
+from IPython.utils.version import check_version
 
 #-----------------------------------------------------------------------------
 # Functions
 #-----------------------------------------------------------------------------
 marked = os.path.join(os.path.dirname(__file__), "marked.js")
+_node = None
 
 __all__ = [
     'markdown2html',
@@ -61,13 +64,31 def markdown2latex(source):
     """
     return pandoc(source, 'markdown', 'latex')
 
+def markdown2html(source):
+    """Convert a markdown string to HTML"""
+    global _node
+    if _node is None:
+        # prefer md2html via marked if node.js >= 0.9.12 is available
+        # node is called nodejs on debian, so try that first
+        _node = 'nodejs'
+        if not _verify_node(_node):
+            _node = 'node'
+            if not _verify_node(_node):
+                warnings.warn(  "Node.js 0.9.12 or later wasn't found.\n" +
+                                "Nbconvert will try to use Pandoc instead.")
+                _node = False
+    if _node:
+        return markdown2html_marked(source)
+    else:
+        return markdown2html_pandoc(source)
+
 def markdown2html_pandoc(source):
     """Convert a markdown string to HTML via pandoc"""
     return pandoc(source, 'markdown', 'html', extra_args=['--mathjax'])
 
 def markdown2html_marked(source, encoding='utf-8'):
     """Convert a markdown string to HTML via marked"""
-    command = [node_cmd, marked]
+    command = [_node, marked]
     try:
         p = subprocess.Popen(command,
                              stdin=subprocess.PIPE, stdout=subprocess.PIPE
@@ -99,18 +120,20 def markdown2rst(source):
     """
     return pandoc(source, 'markdown', 'rst')
 
-# prefer md2html via marked if node.js is available
-# node is called nodejs on debian, so try that first
-node_cmd = 'nodejs'
-try:
-    find_cmd(node_cmd)
-except FindCmdError:
-    node_cmd = 'node'
+def _verify_node(cmd):
+    """Verify that the node command exists and is at least the minimum supported
+    version of node.
+
+    Parameters
+    ----------
+    cmd : string
+        Node command to verify (i.e 'node')."""
     try:
-        find_cmd(node_cmd)
-    except FindCmdError:
-        markdown2html = markdown2html_pandoc
-    else:
-        markdown2html = markdown2html_marked
-else:
-    markdown2html = markdown2html_marked
+        out, err, return_code = get_output_error_code([cmd, '--version'])
+    except OSError:
+        # Command not found
+        return False
+    if return_code:
+        # Command error
+        return False
+    return check_version(out.lstrip('v'), '0.9.12')