How can I format the mercurial "hg log" output easily as parsable JSON?

Question

I would like a command-line example on how to easily use hg log, with hg filters, and output it safely to JSON (with an array that contains the files).

Multi platform (windows/unix) would be great.

Answer 1

Mercurial has built-in support for JSON. You can get log output in JSON format simply by using:

hg log -Tjson

Filters can be used as usual, and to get the files, you can add the '-v' (verbose) parameter.

Note that this is a relatively new feature (see the wiki for more details), which is probably why it's not clearly documented yet.

It's also possible to get xml output using:

hg log -Txml

Answer 2

Edit: this answer here works for any hg version. for newer hg versions (3.1+), see the other answer which is more performant and simpler.

Here is a solid oneliner, as an example.

It uses mercurials hg log, and pipes its output to a python oneliner. The hg log template is configured to output valid python literals. The python oneliner converts it to JSON.

hg log --date ">2014-10-01" --no-merges --keyword "mantis@1953" --keyword "mantis@1955" --template "[\"{node|short}\",\"{author|user|urlescape}\",\"{date|rfc3339date}\",\"{desc|urlescape}\", [{files % '\"{file}\",'}]]\n" --user marinus --user develop | python -c "import sys,ast,json,urllib; x=[[z[0], urllib.unquote(z[1]).decode('utf8'), z[2], urllib.unquote(z[3]).decode('utf8'), z[4]] for z in [ast.literal_eval(y) for y in sys.stdin.readlines()]]; print(json.dumps(x,indent=2))"

The above example is for unix, but you can simply replace \" for "", if you need windows compatibility. It you want unformatted JSON, set 'indent' to None.

The python code is 2/3 compatible (any up-to-date version), and does not use any external modules.

For more explanation of the used hg commands, see:

hg help log
hg help dates
hg help templates

The python code uses nested list comprehensions, google it for more info.