Yarn crashes whenever there is a `.yarnrc.yml` that is not empty but does not set any YAML nodes

[kalrish]

Issue

The corresponding issue template did not set a structure. I can edit this issue's description to match the new repository's issue template for bug reports.

Affected versions

I have run into this issue with version 1.22.19 of Yarn as distributed by Arch Linux on version 20.2.0 of Node.js as distributed by Arch Linux:

pacman --query --owns -- "$(which -- node)"

/usr/bin/node is owned by nodejs 20.2.0-1

pacman --query --owns -- "$(which -- yarn)"

/usr/bin/yarn is owned by yarn 1.22.19-1

Reproduction

Yarn runs fine when there is no .yarnrc.yml:

ls -A
yarn --version

1.22.19

Yarn runs fine when there is an empty .yarnrc.yml:

touch -- .yarnrc.yml
yarn --version

1.22.19

Yarn runs fine when there is a .yarnrc.yml with a single line feed (LF) character:

echo > .yarnrc.yml
yarn --version

1.22.19

Yarn crashes when there is a .yarnrc.yml with two line feed (LF) characters:

echo >> .yarnrc.yml
yarn --version

TypeError: Cannot read properties of null (reading 'yarnPath')
    at loadRcFile (/usr/lib/node_modules/yarn/lib/cli.js:56995:49)
    at /usr/lib/node_modules/yarn/lib/cli.js:56966:14
    at /usr/lib/node_modules/yarn/lib/cli.js:97395:14
    at Array.map (<anonymous>)
    at parseRcPaths (/usr/lib/node_modules/yarn/lib/cli.js:97393:78)
    at Object.findRc (/usr/lib/node_modules/yarn/lib/cli.js:97407:10)
    at getRcConfigForCwd (/usr/lib/node_modules/yarn/lib/cli.js:56965:74)
    at /usr/lib/node_modules/yarn/lib/cli.js:88756:56
    at Generator.next (<anonymous>)
    at step (/usr/lib/node_modules/yarn/lib/cli.js:310:30)

Yarn crashes when there is a .yarnrc.yml with only a comment:

echo '# foobar' > .yarnrc.yml

yarn --version

TypeError: Cannot read properties of null (reading 'yarnPath')
    at loadRcFile (/usr/lib/node_modules/yarn/lib/cli.js:56995:49)
    at /usr/lib/node_modules/yarn/lib/cli.js:56966:14
    at /usr/lib/node_modules/yarn/lib/cli.js:97395:14
    at Array.map (<anonymous>)
    at parseRcPaths (/usr/lib/node_modules/yarn/lib/cli.js:97393:78)
    at Object.findRc (/usr/lib/node_modules/yarn/lib/cli.js:97407:10)
    at getRcConfigForCwd (/usr/lib/node_modules/yarn/lib/cli.js:56965:74)
    at /usr/lib/node_modules/yarn/lib/cli.js:88756:56
    at Generator.next (<anonymous>)
    at step (/usr/lib/node_modules/yarn/lib/cli.js:310:30)

Yarn seems to crash whenever there is a .yarnrc.yml that is not empty but does not set any nodes.

I wrote a reproduction case for Sherlock following the guide:

const fs = require("node:fs");

fs.writeFileSync(
    ".yarnrc.yml",
    "\n",
);

expect(
    yarn(
        "--version",
    ),
)
.resolves
.not
.toThrow(
)
;

Contribution

I would like to propose a fix. Please let me know whether one is desired or this issue does not warrant an update to the otherwise frozen Yarn Classic.

[merceyz]

Fixed in #9009