Pug: using v-slot:slot-name without slot prop results compilation error

[joostdelange]

Describe the bug

When using pug in my Vue component templates, and calling a named slot using the v-slot syntax I ran into some problems when using it without a slot prop.

The following is a happening:

• This works: template(v-slot:slot-name="slotProp")
• This does not: template(v-slot:slot-name)

This bug occurred in version 1.x already and was solved in #634,
so I'm confident it can be fixed in v2.x too.

Reproduction

https://github.com/joostdelange/vite-beta-pug-slot-bug

System Info

• vite version: v2.0.0-beta.7
• vue version: v3.0.5
• pug version v3.0.0
• Operating System: macOS
• Node version: v14.15.1
• Package manager (npm/yarn/pnpm) and version: npm v6.14.10

Logs (Optional if provided reproduction)

1. Run vite or vite build with the --debug flag.
2. See the error: Cannot read property 'length' of undefined