Jinja2++
Jinja2++ is a drop in single file solution for templating with Variable Precedence.
You can use ANY language!
How it works
Based on the Unix pipeline : JSON - stdin |> stdout - JSON
A var_file is any executable that slurps JSON from STDIN, and spits JSON from STD out.
We assemble a series of cascading var_files based on the file hierarchy to overwrite proceeding variables.
We also do context injection, in the same fashion, ie context as the local path of each var_file / template, etc
Features
Variable precedence
src
|── vars.perl* <- [[base variables]]
├── filters.py* <- inject ((J2 filters)) with ~vanilla python~ functions!
...
├── render_inject.rb* <- inject && overwrite [pre-render context] variables
├── var_inject.sh* <- inject && overwrite [pre-script context] variables
...
├── monitoring/
│ ├── grafana/
│ │ ├── templates/
│ │ ├── Chart.yaml.j2
│ │ └── vars.js* <- [overwrite] variables here
│ ├── iperf/
│ │ ├── templates/
│ │ ├── Chart.yaml.j2
│ │ └── vars.fsi* <- [overwrite] variables here
│ ├── prometheus/
│ │ ├── templates/
│ │ ├── Chart.yaml.j2
│ │ └── vars.exe* <- [overwrite] variables here
...
Dry runs
Syntax highlighted diff
Dynamic J2 filter import
Write your filters as vanilla Python functions.
like so:
def drop_first(lst):
return lst[1:]
def base64(x, indent=0):
encoded = str(b64.b64encode(x.strip().encode("utf-8")), "utf-8")
return (" " * indent) + (encoded if encoded else "")
Context injection
The following [context variables] will be injected before each var_file / template.
add more of your own!
{"src": "...",
"_dest_": "...",
"_dir_": "...",
"_parent_": "...",
"_grand_parent_": "...",
"_var_file_/_template_": "..."}
Usage
Simply call ./j2pp.py with the following:
Note: For large projects you may need to call ulimit -S -n <number> to increase # of concurrent open files by a unix process.
This is required prior to calling ./j2pp.py due to the fact that it does parallel processing.
Arguments
--src
Put all your .j2 templates here, along with var_files.
--out
Your finished templates go here.
--exclude
Any file paths in exclude will be skipped. i.e. --exclude .s .skip
--var-files
A VAR_FILE is an executable: .py, .sh, et al.
VAR_FILES are how you do variable injections.
JSON - stdin |> stdout - JSON.
VAR_FILES are placed in the file hierarchy
beween *.j2 and SRC.
VAR_FILES closes to *.j2 have higher precedence.
--import-filters
All functions in IMPORT_FILTERS will be included as
j2 filters. Must be python files.
--inject-before-vars
Same semantics as VAR_FILES,
except run before each VAR_FILE.
--inject-before-render
Same semantics as VAR_FILES,
except run before each .j2 file is rendered.
--extra-vars
Inject variables with JSON.
Highest precedence, also available to all var files.
--delimiter
Default is ?.
Any stdout in VAR_FILES before the last occurance
of ? will be treated as comments.
? is entirely optional.
--dry-run
Just do a diff, dont write to file.
--no-diffs
Dont print diff.
--formatter
Used to print diff, if your terminal is kinda wonky,
pick one with less colours.
