Feature/custom loader (#2)

* [#1] add possibility to override env

Also provides an example of how to implement a custom loader
Fixes #1

* update docs to match new endpoint filename

* add doc about custom loader

* fix link

README.md

@@ -4,13 +4,23 @@ Every now and then, it's pretty useful to just have a cli tool that does the job
 
 ## Usage: ##
 ```
-python j2-lint.py my-template.j2
+python j2lint.py my-template.j2
 ```
 
 It accepts multiple arguments so shell expansion and/or combining with find is no issue:
 
 ```
-python j2-lint.py *.j2
-find src -type f -name "*.j2" -exec python j2-lint.py '{}' +
+python j2lint.py *.j2
+find src -type f -name "*.j2" -exec python j2lint.py '{}' +
 ```
 
+## Usage with custom filters, tests, etc ##
+
+If you want to use this linter with custom filters, tests, etc, you can easily
+extend the main cli endpoint by passing in a `env` keyword argument.
+
+The file [custom_check_example.py](custom_check_example.py) provides a working example for the filter
+'to_nice_json'. 
+
+Note that for linting it is not necessary to refer to the actual implementation
+of the filters, jinja2 only needs to know they exist.

custom_check_example.py

@@ -0,0 +1,13 @@
+"""
+This is an example of how to extend the default environment
+and/or loader to add your own filter logic.
+"""
+import jinja2
+from j2lint import main, AbsolutePathLoader
+
+filters = ['to_nice_json']
+
+env = jinja2.Environment(loader=AbsolutePathLoader())
+env.filters.update({name: lambda: None for name in filters})
+
+main(env=env)

j2-lint.py → j2lint.py

@@ -1,5 +1,5 @@
 """
-@author Gerard van Helden <gerard@zicht.nl>
+@author Gerard van Helden <drm@melp.nl>
 @license DBAD, see <http://www.dbad-license.org/>
 
 Simple j2 linter, useful for checking jinja2 template syntax
@@ -19,9 +19,7 @@ def get_source(self, environment, path):
         return source, path, lambda: mtime == os.path.getmtime(path)
 
 
-def check(template, out, err):
-    env = jinja2.Environment(loader=AbsolutePathLoader())
-
+def check(template, out, err, env=jinja2.Environment(loader=AbsolutePathLoader())):
     try:
         env.get_template(template)
         out.write("%s: Syntax OK\n" % template)
@@ -33,11 +31,13 @@ def check(template, out, err):
         err.write("%s: Syntax check failed: %s in %s at %d\n" % (template, e.message, e.filename, e.lineno))
         return 1
 
-
-if __name__ == "__main__":
+def main(**kwargs):
     import sys
-
     try:
-        sys.exit(reduce(lambda r, fn: r + check(fn, sys.stdout, sys.stderr), sys.argv[1:], 0))
+        sys.exit(reduce(lambda r, fn: r + check(fn, sys.stdout, sys.stderr, **kwargs), sys.argv[1:], 0))
     except IndexError:
-        sys.stdout.write("Usage: j2-lint.py filename [filename ...]\n")
+        sys.stdout.write("Usage: j2lint.py filename [filename ...]\n")
+
+if __name__ == "__main__":
+    main()
+