Error generating metadata in test_component (status=255)

[Mark-Abadir]

Hello,
I have been having an issue with the dash component boilerplate not generating my components. When I execute

npm run build

It generates the following error

`Error generating metadata in test_component (status=255)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! test_component@0.0.1 build:py_and_r: dash-generate-components ./src/lib/components test_component -p package-info.json --r-prefix ''
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the test_component@0.0.1 build:py_and_r script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! C:\Users\mabadir\AppData\Roaming\npm-cache_logs\2020-06-15T15_43_13_527Z-debug.log
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! test_component@0.0.1 build: npm run build:js && npm run build:py_and_r
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the test_component@0.0.1 build script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! C:\Users\mabadir\AppData\Roaming\npm-cache_logs\2020-06-15T15_43_13_559Z-debug.log

To test whether this was something that was wrong with my javascript, I ran the cookiecutter command again in a new python project to create a new component. For set up I selected the following

You've downloaded C:\Users\mabadir.cookiecutters\dash-component-boilerplate before. Is it okay to delete and re-download it? [yes]:
project_name [my dash component]: Test Component
project_shortname [test_component]:
component_name [TestComponent]:
r_prefix []:
author_name [Enter your first and last name (For package.json)]: MA
author_email [Enter your email (For package.json)]: ma
github_org []:
description [Project Description]: testing
Select license:
1 - MIT License
2 - BSD License
3 - ISC License
4 - Apache Software License 2.0
5 - GNU General Public License v3
6 - Not open source
Choose from 1, 2, 3, 4, 5, 6 [1]:
publish_on_npm [True]: False
install_dependencies [True]:
Executing: c:\python38\python.exe -m venv venv

From there I tried npm run build on the example javascript component provided, and it still gave me the above error. Can you please advise?

Edit: Forgot to mention that it was working before.

[alexcjohnson]

Thanks @Mark-Abadir - is there any more to the error message than that? Can you describe your environment? I just ran a plain cookiecutter https://github.com/plotly/dash-component-boilerplate.git followed by npm run build on my mac, and it all seemed to work fine, but I could certainly imagine there being platform-specific issues.

[RobAlonzi]

This happens to me as well, running a brand new cookiecutter https://github.com/plotly/dash-component-boilerplate.git followed by npm run build

Webpack seems to be outputting normally:

webpack --mode production
Hash: ef69a9576f2095a97ace
Version: webpack 4.36.1
Time: 492ms
Built at: 06/22/2020 1:14:17 AM
Asset Size Chunks Chunk Names
test_proj.min.js 3.16 KiB 0 [emitted] main
test_proj.min.js.map 7.38 KiB 0 [emitted] main
Entrypoint main = test_proj.min.js test_proj.min.js.map
[0] external "PropTypes" 42 bytes {0} [built]
[1] external "React" 42 bytes {0} [built]
[2] ./src/lib/index.js + 1 modules 5.04 KiB {0} [built]
| ./src/lib/index.js 122 bytes [built]
| + 1 hidden module

This seems to error out:

test_proj@0.0.1 build:py_and_r /media/data/Dev/Projects/dash-hello-world/test_proj
dash-generate-components ./src/lib/components test_proj -p package-info.json --r-prefix 'r_'

Traceback (most recent call last):
File "/home/rob/.local/bin/dash-generate-components", line 11, in
sys.exit(cli())
File "/home/rob/.local/lib/python2.7/site-packages/dash/development/component_generator.py", line 194, in cli
rsuggests=args.r_suggests,
File "/home/rob/.local/lib/python2.7/site-packages/dash/development/component_generator.py", line 90, in generate_components
metadata = safe_json_loads(out.decode("utf-8"))
File "/home/rob/.local/lib/python2.7/site-packages/dash/development/component_generator.py", line 132, in safe_json_loads
jsondata_unicode = json.loads(s, object_pairs_hook=OrderedDict)
File "/usr/lib/python2.7/json/init.py", line 352, in loads
return cls(encoding=encoding, **kw).decode(s)
File "/usr/lib/python2.7/json/decoder.py", line 364, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/usr/lib/python2.7/json/decoder.py", line 382, in raw_decode
raise ValueError("No JSON object could be decoded")

ValueError: No JSON object could be decoded

Looks like some JSON is missing? I am running on Ubuntu 18.04.4 LTS

[RobAlonzi]

For me, it was a false alarm, I had to make sure I was in the venv before I ran npm run build

In the project root, source venv/bin/activate, then npm run build worked for me.

@Mark-Abadir, I hope this helps you as well.

[Mark-Abadir]

Sorry for the delayed response.

@alexcjohnson That is the entire error message. I tried using npm run build with python 2.7 and python 3.8. Same error message both times. Both have dash as part of the included packages.
ch
@RobAlonzi Thanks for the advice but I didn't get that error specifically. And source venv/bin/activate didn't change anything for me

[xhluca]

Hi Mark, here's exactly what I did wrote in the terminal (Ubuntu), and I had no error:

$ cookiecutter https://github.com/plotly/dash-component-boilerplate.git
project_name [my dash component]: 
project_shortname [my_dash_component]: 
component_name [MyDashComponent]: 
r_prefix []: 
author_name [Enter your first and last name (For package.json)]: Xing Han
author_email [Enter your email (For package.json)]: xinghan@plot.lly
github_org []: 
description [Project Description]: 
Select license:
1 - MIT License
2 - BSD License
3 - ISC License
4 - Apache Software License 2.0
5 - GNU General Public License v3
6 - Not open source
Choose from 1, 2, 3, 4, 5, 6 [1]: 
publish_on_npm [True]: 
install_dependencies [True]: 
Executing: /home/xhlu/miniconda3/bin/python -m venv venv

Installing dependencies
<...>

$ cd my_dash_components/
$ source venv/bin/activate
$ npm i
$ npm run build:all

I noticed you are running on Windows. Have you tried Windows Subsystem for Linux (WSL) 2.0? If I remember correctly, source venv/bin/activate does not work in a Win10 command prompt, so maybe you have to use venv\Scripts\activate.bat instead?