I'm using jsonnet to build json objects that will be used by Python code, calling jsonnet from Python using the bindings. I want to set up my directory structure so that the jsonnet files are in a subdirectory or subdirectories relative to where the Python code is run, something like:
foo.py
jsonnet/
jsonnet/bar.jsonnet
jsonnet/baz.libsonnet
Running foo.py
should then be able to use _jsonnet.evaluate_snippet()
on strings read from files in jsonnet/
that import other files from jsonnet/
. What's the best way to do this?
The default importer uses paths relative to the file from which they are imported. In case of evaluate_snippet
you need to pass the path manually. This way jsonnet knows where to look for imported files.
If your intention is to process the files you can use a custom importer. (Digression: jsonnet tries to avoid the need to preprocess the source files, so there is probably a better way or a missing feature in jsonnet.)
Below is the complete, working example on how to use custom importers in Python (adjusted to the directory structure provided):
import os
import unittest
import _jsonnet
# Returns content if worked, None if file not found, or throws an exception
def try_path(dir, rel):
if not rel:
raise RuntimeError('Got invalid filename (empty string).')
if rel[0] == '/':
full_path = rel
else:
full_path = dir + rel
if full_path[-1] == '/':
raise RuntimeError('Attempted to import a directory')
if not os.path.isfile(full_path):
return full_path, None
with open(full_path) as f:
return full_path, f.read()
def import_callback(dir, rel):
full_path, content = try_path(dir, rel)
if content:
return full_path, content
raise RuntimeError('File not found')
class JsonnetTests(unittest.TestCase):
def setUp(self):
self.input_filename = os.path.join(
"jsonnet",
"bar.jsonnet",
)
self.expected_str = '{\n "num": 42,\n "str": "The answer to life ..."\n}\n'
with open(self.input_filename, "r") as infile:
self.input_snippet = infile.read()
def test_evaluate_file(self):
json_str = _jsonnet.evaluate_file(
self.input_filename,
import_callback=import_callback,
)
self.assertEqual(json_str, self.expected_str)
def test_evaluate_snippet(self):
json_str = _jsonnet.evaluate_snippet(
"jsonnet/bar.jsonnet",
self.input_snippet,
import_callback=import_callback,
)
self.assertEqual(json_str, self.expected_str)
if __name__ == '__main__':
unittest.main()
Note: it's a modified version of an example from jsonnet repo.