`install.sh` fails with npm when YARN_PATH environment variable is not defined

[RobinzZH]

Installation of code-server via install.sh fails on docker images.

code-server/install.sh

Lines 422 to 423 in ad81a30

	YARN_PATH="${YARN_PATH-yarn}"
	NPM_PATH="${YARN_PATH-npm}"

Steps to Reproduce

$ docker run -it alpine
/ # apk add nodejs npm curl
...
/ # node -v
v14.18.1
/ # npm -v
7.17.0
/ # curl -fsSL https://code-server.dev/install.sh | sh
Alpine Linux v3.14
Installing latest from npm.

Please install npm or yarn to install code-server!
You will need at least node v12 and a few C dependencies.
See the docs https://coder.com/docs/code-server/latest/install#yarn-npm
/ # 

Expected

Code-server should get installed.

Actual

Installation fails and I get the following output:

# printenv 
  418  install_npm() {
  419    echoh "Installing latest from npm."
  420    echoh
  421
  422    YARN_PATH="${YARN_PATH-yarn}"
  423    NPM_PATH="${YARN_PATH-npm}"
  424
  425    echoh YARN_PATH=$YARN_PATH
  426    echoh NPM_PATH=$NPM_PATH

/ # sh ./install.sh 
Alpine Linux v3.14
Installing latest from npm.

YARN_PATH=yarn
NPM_PATH=yarn
Please install npm or yarn to install code-server!
You will need at least node v12 and a few C dependencies.
See the docs https://coder.com/docs/code-server/latest/install#yarn-npm
/ # 

[jsjoeio]

Weird. This is unexpected. Thanks for the detailed report. If npm is installed, we should be using that to install code-server, not erroring if yarn isn't available.

cc @code-asher (thought you would find this interesting).

[stale]

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