simple_json_from_html_string(...) with use_readability=True is not multi-thread/process safe

[erpic]

If called from multiple threads or processes, multiple inputs will collide into the same "full.html" / "article.json" on the filesystem and erroneous responses will be returned.

This is due to this in 'simple_json_from_html_string_safe()':

    if use_readability:
        temp_dir = tempfile.gettempdir()
        # Write input HTML to temporary file so it is available to the node.js script
        html_path = os.path.join(temp_dir, "full.html")
        with open(html_path, 'w') as f:
            f.write(html)

        # Call Mozilla's Readability.js Readability.parse() function via node, writing output to a temporary file
        article_json_path = os.path.join(temp_dir, "article.json")
        jsdir = os.path.join(os.path.dirname(__file__), 'javascript')
        with chdir(jsdir):
            subprocess.check_call(["node", "ExtractArticle.js", "-i", html_path, "-o", article_json_path])

        # Read output of call to Readability.parse() from JSON file and return as Python dictionary
        with open(article_json_path) as f:
            input_json = json.loads(f.read())

here tempfile.gettempdir() is global, for example "/tmp"
there will be collisions in "/tmp/full.html" and "/tmp/article.json"

possible fix, add 'use_readability_temp_dir' like so:

def simple_json_from_html_string_safe(html, content_digests=False, node_indexes=False, use_readability=False, use_readability_temp_dir=None):

    if use_readability:
        temp_dir = use_readability_temp_dir or tempfile.gettempdir()  # if no specific temp_dir is provided use global system temp dir, this will cause collisions in multiprocess situations
        ...

then use like so:

with tempfile.TemporaryDirectory(prefix="readabilipy", delete=True) as temp_dir:  # create a unique temp dir
    res = simple_json_from_html_string_safe(html, use_readability=True, use_readability_temp_dir=temp_dir

[jemrobinson]

@erpic: This project is no longer actively developed. If you are happy to make a PR with this fix, I'm happy to review and merge it when I have some free time.

[erpic]

@jemrobinson will do, many thanks.

Any preference between the approach above (minimal change but you have to explicitely set 'use_readability_temp_dir' to be thread safe) or touching a couple more lines so and we always create a unique temp dir within that function and then it's always thread safe (that seems better to me)?

[jemrobinson]

Yes - the second one sounds better to me too. Thanks!

[erpic]

@jemrobinson here is a pull request
I believe this can be merged as is. But note that tests fail (before and after these changes, but after the merge this is really extra linebreaks)

#110

many thanks for your support on this great and useful package!