TS 3.7: --declaration output for getter only property now is a getter instead of `readonly`

[mjbvz]

TypeScript Version: 3.7.0-dev.20191010

Search Terms:

• --declaration
• getter
• d.ts

Repo:
For the TS file foo.ts:

export class Foo {
    get bar(): boolean { return true; }
}

1. Run tsc foo.ts --declaration

Expected
In TS 3.6, the output d.ts uses readonly:

export declare class Foo {
    readonly bar: boolean;
}

Actual behavior:
In TS 3.7, the output d.ts use a getter instead:

export declare class Foo {
    get bar(): boolean;
}

[Jessidhia]

That is an intentional change done as part of #27644 that, it seems, was missed from the 3.7 blog post.

See also #33509 and #33880

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.

[AndreasGassmann]

I just noticed this as well. The problem is that when I use our own library with the "getter-syntax", I get an error:

error TS1086: An accessor cannot be declared in an ambient context.

What is the recommended way of getting around that?

[matthiasg]

I have the same issue with 3.7 .. importing the types is now not possible

[AndreasGassmann]

@matthiasg It seems that they knew the typings were incompatible. I'm quite surprised that there was no mention of this anywhere (or did I overlook it?). #33470

I ended up writing a small script for our CI that replaces the new syntax with the old one as a temporary solution.

[GordonSmith]

This will prevent my library from upgrading to 3.7.x until all my customers are also using 3.7.x (and they include Angular folks who won't be upgrading Angular anytime soon).
Given this is a breaking change shouldn't it have waited until 4.x.x?

[paulquinn]

I'm also getting TS1086 when trying to use npm libraries with the "getter syntax" - could someone please give some guidance around this/can this be reopended?

[bcoe]

This seems like a fairly significant breaking change, and is biting a lot of our customer:

googleapis/node-gtoken#244

I understand it's working as intended, but I question why this was released in a minor release of the library, vs., a 4.x release like @GordonSmith mentions.

[paulquinn]

@RyanCavanaugh is there any other any guidance here (other than re-target to 3.6 or lower)? At least this should be documented somewhere... this is blocking up from using libraries compiled with 3.7 with our current Angular projects.

[endel]

Also having the same issue in an Angular project.

[bcrosnier]

Also got bit by the sudden breaking change through an Angular project (TS 3.5) referencing a library built by 3.7 with breaking definitions.

Solved by bashing the library provider until he rolled back to TS 3.6.

Just for reference, TS 3.7 support in Angular projects is handled by angular/angular-cli#16071.