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python-3.xdockerjinja2cookiecutter

Jinja2 Templates Not Rendering for Cookiecutter Using Docker

I am trying to generate a project template using cookiecutter through a Docker container and the jinja2 templates I provide in the values of the cookiecutter.json file don’t appear to render properly.

The goal of this is to allow anyone to run a simple Docker command to generate a template without having to first install cookiecutter on their machine.

Here is my workflow and output.

Setup

I have the following project structure

mldev_template/
├── Dockerfile.cookiecutter
├── entrypoint.sh
├── cookiecutter.json
└── {{cookiecutter._project_name_snake_case}}/
    ├── Dockerfile

The files contain the following:

Dockerfile.cookiecutter

FROM python:3.10.8
RUN pip install cookiecutter==2.6.0

WORKDIR /workspace/mldev_template

COPY entrypoint.sh /workspace/mldev_template/entrypoint.sh

RUN chmod +x /workspace/mldev_template/entrypoint.sh
ENTRYPOINT ["/workspace/mldev_template/entrypoint.sh"]

entrypoint.sh

#!/bin/bash

cookiecutter -v /workspace/mldev_template

cookiecutter.json

{
    "project_name": "My Awesome Project",
    "_project_name_snake_case": "{{ cookiecutter.project_name | lower | replace(' ', '_') }}"
}

I have also tried cookiecutter.project_name.lower().replace(' ', '_') as well as jinja2-strcase functions in place of this jinja2 template with the same results.

{{cookiecutter._project_name_snake_case}}/Dockerfile

FROM python:3.10-slim
LABEL project="{{ cookiecutter._project_name_snake_case }}"

Expectations

I am expecting the jinja2 templates to render as the directory name of the newly generated directory and in the project LABEL of the Dockerfile inside the newly generated directory, both as snake case.

In my example below I input Test Project at the prompt, so I would expect to see test_project as the directory name and the project LABEL in the newly generated Dockerfile.

Workflow

I ran the following commands to build the Docker image on my local machine, and then ran a container interactively. These commands were run from inside the top-level directory.

docker build --no-cache -f Dockerfile.cookiecutter -t cookiecutter-runner .

docker run -it --rm -v $(pwd)/..:/workspace --entrypoint /bin/bash cookiecutter-runner

Once inside the container I run cookiecutter -v /workspace/mldev_template, follow the prompt, and get the following output.

root@345df12673ac:/workspace/mldev_template# cookiecutter -v /workspace/mldev_template
DEBUG cookiecutter.config: User config not found. Loading default config.
DEBUG cookiecutter.hooks: hooks_dir is /workspace/mldev_template/hooks
DEBUG cookiecutter.hooks: No hooks/dir in template_dir
DEBUG cookiecutter.main: context_file is /workspace/mldev_template/cookiecutter.json
DEBUG cookiecutter.generate: Context generated is OrderedDict([('cookiecutter', OrderedDict([('project_name', 'My Awesome Project'), ('_project_name_snake_case', "{{ cookiecutter.project_name | lower | replace(' ', '_') }}")]))])
  [1/1] project_name (My Awesome Project): Test Project
DEBUG cookiecutter.main: context is OrderedDict([('cookiecutter', OrderedDict([('project_name', 'Test Project'), ('_project_name_snake_case', "{{ cookiecutter.project_name | lower | replace(' ', '_') }}")])), ('_cookiecutter', {'project_name': 'My Awesome Project'})])
DEBUG cookiecutter.utils: Making sure path exists (creates tree if not exist): /root/.cookiecutter_replay/
DEBUG cookiecutter.find: Searching /workspace/mldev_template for the project template.
DEBUG cookiecutter.find: The project template appears to be /workspace/mldev_template/{{ cookiecutter._project_name_snake_case }}
DEBUG cookiecutter.generate: Generating project from /workspace/mldev_template/{{ cookiecutter._project_name_snake_case }}...
DEBUG cookiecutter.generate: Rendered dir {{ cookiecutter.project_name | lower | replace(' ', '_') }} must exist in output_dir .
DEBUG cookiecutter.utils: Making sure path exists (creates tree if not exist): {{ cookiecutter.project_name | lower | replace(' ', '_') }}
DEBUG cookiecutter.generate: Project directory is /workspace/mldev_template/{{ cookiecutter.project_name | lower | replace(' ', '_') }}
DEBUG cookiecutter.hooks: hooks_dir is /workspace/mldev_template/hooks
DEBUG cookiecutter.hooks: No hooks/dir in template_dir
DEBUG cookiecutter.hooks: No pre_gen_project hook found
DEBUG cookiecutter.generate: Processing file Dockerfile
DEBUG cookiecutter.generate: Created file at /workspace/mldev_template/{{ cookiecutter.project_name | lower | replace(' ', '_') }}/Dockerfile
DEBUG cookiecutter.generate: Check Dockerfile to see if it's a binary
DEBUG cookiecutter.generate: Using detected newline character '\n'
DEBUG cookiecutter.generate: Writing contents to file /workspace/mldev_template/{{ cookiecutter.project_name | lower | replace(' ', '_') }}/Dockerfile
DEBUG cookiecutter.hooks: hooks_dir is /workspace/mldev_template/hooks
DEBUG cookiecutter.hooks: No hooks/dir in template_dir
DEBUG cookiecutter.hooks: No post_gen_project hook found

Results

A new directory is created but the new directory is named {{ cookiecutter.project_name | lower | replace(' ', '_') }} instead of test_project and the Dockerfile beneath it looks like this

FROM python:3.10-slim
LABEL project="{{ cookiecutter.project_name | lower | replace(' ', '_') }}"

Is there something else I need to do to make these jinja2 templates render properly using cookiecutter? I can’t seem to find any information about this anywhere. This is my first time using cookiecutter and jinja2 in general so I’m probably missing something super simple, but I can’t seem to find an example that generates cookiecutter using Docker and I can’t seem to find an example where someone else’s jinja2 templates don’t render properly.

I also verified that when I build my Docker image all requirements to run cookiecutter are properly installed.

Package         Version Latest Version
MarkupSafe  2.1.5   2.1.5
PyYAML  6.0.1   6.0.1
arrow   1.3.0   1.3.0
binaryornot 0.4.4   0.4.4
certifi 2024.6.2    2024.6.2
chardet 5.2.0   5.2.0
charset-normalizer  3.3.2   3.3.2
click   8.1.7   8.1.7
cookiecutter    2.6.0   2.6.0
idna    3.7 3.7
jinja2  3.1.4   3.1.4
jinja2-strcase  0.0.2   0.0.2
markdown-it-py  3.0.0   3.0.0
mdurl   0.1.2   0.1.2
pip 23.0.1  24.0
pygments    2.18.0  2.18.0
python-dateutil 2.9.0.post0 2.9.0.post0
python-slugify  8.0.4   8.0.4
requests    2.32.3  2.32.3
rich    13.7.1  13.7.1
setuptools  58.1.0  70.0.0
six 1.16.0  1.16.0
text-unidecode  1.3 1.3
types-python-dateutil   2.9.0.20240316  2.9.0.20240316
urllib3 2.2.2   2.2.2
wheel   0.43.0  0.43.0
Solution

  • The following worked for me using jinja2_strcase library (https://pypi.org/project/jinja2-strcase/)

    1. Add "_extensions": ["jinja2_strcase.StrcaseExtension"] to cookiecutter.json

    2. Add jinja2-strcase==0.0.2 to Dockerfile install

    3. Use {{cookiecutter.project_name | to_snake }}, {{cookiecutter.project_name | to_camel }}, etc. throughout template

    4. Make entrypoint.sh executable outside of Dockerfile