fix(language-service): use single entry point for Ivy and View Engine

[kyliau]

Currently there are two entry points for the @angular/language-service
package:

• @angular/language-service
  This default entry point is for View Engine LS. Through the redirection
  of main field in package.json, it resolves to
  ./bundles/language-service.js.
• @angular/language-service/bundles/ivy.js
  This secondary entry point is for Ivy LS.

TypeScript recently changed the behavior of tsserver to allow only package
names as plugin names 1 for security reasons. This means the secondary
entry point for Ivy LS can no longer be used.
We implemented a quick hack in the module resolver (in the extension repo)
to fix this, but the long term fix should be in @angular/language-service.

Here, the main field in package.json is changed to index.js, and in the
index file we conditionally load View Engine or Ivy based on the input config.
This eliminates the need for multiple entry points.

As part of this PR, I also removed all source code for View Engine and Ivy
included in the NPM package. Consumers of this package should run the bundled
output and nothing else. This would help us prevent an accidental import that
results in execution of unbundled code.

The new layout of the NPM package is as follows:

@angular/language-service
├── api.d.ts
├── api.js
├── bundles
│   ├── ivy.js
│   └── language-service.js
├── index.d.ts
├── index.js
└── package.json

cc: @ivanwonder

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.io application / infrastructure changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[atscott]

Hmm, this is a little bit awkward given that you have to call create first but I can't think of a better way...

[ivanwonder]

Whether we can assert the plugin has been created by tsserver. If not, the tsserver cannot invoke the function.

https://github.com/microsoft/TypeScript/blob/5280ba400c071c87e6ba25c7d8d1ac9c304fe2d4/src/server/project.ts#L1645-L1651

[atscott]

Quick question @kyliau - would this be considered a breaking change since it changes the "main" property in package.json? Or is there another reason this targets major only?

[ivanwonder]

angular/packages/language-service/bundles/BUILD.bazel

Line 6 in a6971ba

entry_point = "//packages/language-service:index.ts",

@kyliau the entry_point is wrong for ve bundles.

[gkalpak]

LGTM 👍
(Just a couple of question - out of curiosity mostly 🧐)

Reviewed-for: dev-infra

[kyliau]

Quick question @kyliau - would this be considered a breaking change since it changes the "main" property in package.json? Or is there another reason this targets major only?

@atscott It's technically not a breaking change since @angular/language-service is considered a "private" package, much like @angular/compiler-cli. But since I'm making drastic changes to the package contents (removed all source files), I don't feel comfortable doing it in a patch release.

[kyliau]

angular/packages/language-service/bundles/BUILD.bazel

Line 6 in a6971ba

entry_point = "//packages/language-service:index.ts",

@kyliau the entry_point is wrong for ve bundles.

@ivanwonder Thanks for pointing that out, I've fixed the entry point :)

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