🏗 Debounce all watch operations in the AMP dev toolchain

[rsimha]

Background:

Several tasks in AMP's gulp toolchain provide watch functionality to enable rebuild-on-edit behavior. However, if a file is saved more than once in a short interval (e.g. hitting Ctrl+S twice in succession), the watcher function is kicked off more than once, which can lead to races in file writes.

PR highlights:

• Uses debounce for instances of watchify and gulp-watch that use a simple watcher function
• Uses gulp-debounce for the one instance of gulp-watch that operates on the gulp stream
• Drive-by minor cleanup of helpers.js, dist.js and lint.js

Tasks fixed by this PR:

# Implicit watch
gulp
gulp serve

# Explicit watch
gulp build --watch
gulp dist --watch
gulp lint --watch

Fixes #27722

[dreamofabear]

Thanks for the fix! Looks reasonable to me though not familiar with this code.

Not sure why the double-save consistently happens for me. Might be related to "on save" actions from ESLint/Prettier plugins in VSCode.

[rsimha]

Thanks for the fix! Looks reasonable to me though not familiar with this code.

Added @estherkim for overall build-system/ review.

Not sure why the double-save consistently happens for me. Might be related to "on save" actions from ESLint/Prettier plugins in VSCode.

@choumx The editor.codeActionsOnSave setting has been enabled for users of the eslint plugin via amphtml/.vscode/settings.json.

amphtml/.vscode/settings.json

Line 22 in 9cc61e6

"editor.codeActionsOnSave": {"source.fixAll.eslint": true},

Could it be that in addition to this, you also have editor.formatOnSave enabled in the settings.json for your local workspace?

[rsimha]

Bumping this since it lacks an approving review.

/cc @ampproject/wg-infra