🏗 Replace gulp with the amp task runner

[rsimha]

This PR replaces gulp with a lightweight task runner with a single-file implementation.

PR highlights:

• Introduce a new amp task runner based on the commander CLI interface
• Remove gulpfile.js and uninstall gulp from the root package.json
• Create identical amp equivalents for all existing gulp commands
• Create a wrapper called gulp that redirects to amp after printing a deprecation notice
• Update the codebase and replace references to gulp commands with their amp equivalents

Notes:

• Backwards compatibility is maintained: existing gulp commands will continue to work via the amp task runner
• No extra installation steps required (sync repo, run npm install, and carry on)

Reasons behind the choice of commander:

• The most popular NodeJS compatible CLI solution (50M downloads / week)
• Flexible in how tasks are defined / configured / run
• High degree of compatibility with the existing UX of AMP's gulp-based dev tools
• Built-in support for task discovery and usage help (via auto-generated --help)
• Package has a tiny footprint (60KB) compared to gulp (multiple MB + dependencies)
• Task start-up is near instant compared to gulp

Screenshots:

New interface: amp

Deprecation notice: gulp

Top-level help: amp --help

Task-level help: amp dist --help

Unknown task: amp foo

Invalid invocation: amp lint --foo --bar

First-time install with global gulp-cli: npm i

First-time install without global gulp-cli: npm i

Subsequent install: npm i

Fixes #32585

[amp-owners-bot]

Hey @danielrozenberg! These files were changed:

build-system/compile/internal-version.js
build-system/tasks/visual-diff/index.js
build-system/tasks/visual-diff/package-lock.json
build-system/tasks/visual-diff/package.json

Hey @alanorozco! These files were changed:

build-system/server/app-index/settings.js
build-system/tasks/markdown-toc/README.md
build-system/tasks/markdown-toc/index.js
build-system/tasks/markdown-toc/test/all-are-complete/allows-paragraph-after-list.md
build-system/tasks/markdown-toc/test/all-are-complete/arbitrary-header-indentation.md
build-system/tasks/markdown-toc/test/all-are-complete/complete.md
build-system/tasks/markdown-toc/test/all-are-complete/ignores-unparsable-options.md
build-system/tasks/markdown-toc/test/all-are-complete/uses-options.md
build-system/tasks/markdown-toc/test/some-are-incomplete/complete.md
build-system/tasks/markdown-toc/test/some-are-incomplete/incomplete.md
build-system/tasks/storybook/index.js
build-system/tasks/storybook/package-lock.json
+1 more

Hey @estherkim! These files were changed:

build-system/tasks/e2e/DEBUGGING.md
build-system/tasks/e2e/README.md
build-system/tasks/e2e/index.js
build-system/tasks/e2e/package-lock.json
build-system/tasks/e2e/package.json
build-system/tasks/e2e/repl.js

Hey @gmajoulet, @processprocess, @t0mg! These files were changed:

extensions/amp-story-360/0.1/amp-story-360.js

Hey @Enriqe! These files were changed:

src/amp-story-player/README.md

Hey @ampproject/wg-caching! These files were changed:

validator/js/engine/validator_test.js

[rsimha]

This PR is ready for preliminary review while I iron out any issues found during CI.

Reviewer notes:

• The meat of this PR lies in the commit titled "Replace gulp with the amp task runner"
• The majority of the remaining changes merely replace the word gulp with amp in JS files and docs
• Adding infra team members for full review of that commit + skim through everything else
• Adding non-infra folks for general comment on the new interface

[samouri]

Is there any difference in speed?

[honeybadgerdontcare]

Approved for validator. There's a couple of internal docs that I'll update once this is merged.

Also second Daniel's comment, can we remove gulp as a required install? If so I'll update our new dev docs internally.

[rsimha]

Is there any difference in speed?

With amp, startup while invoking a task is near instant. With gulp, it would take ~1s before there was any output. Not a huge difference to longer running tasks, but short ones like clean now run in under 20ms.

Also second Daniel's comment, can we remove gulp as a required install? If so I'll update our new dev docs internally.

The idea of this PR is to no longer require the gulp library for AMP development. Daniel's comment called out the fact that I am forcibly replacing the global gulp-cli with our redirection wrapper. I'm going to attempt to find a less invasive way of doing this.

[estherkim]

Awesome! Some nits.

[kristoferbaxter]

install-task-runner.js appears to have resolved my concern from earlier.

Nice work Raghu!

[rsimha]

All CI jobs are green, and I've re-tested the transition paths with and without global installs of gulp-cli and gulp. I'm going to merge this (🤞) and send out a PSA.