TS2430: Interface 'Dockerfile' incorrectly extends interface 'ImageTemplate'

[robcresswell]

Running tsc seems to cause build errors when consuming the library.

node_modules/dockerfile-ast/lib/main.d.ts:30:18 - error TS2430: Interface 'Dockerfile' incorrectly extends interface 'ImageTemplate'.
  Types of property 'resolveVariable' are incompatible.
    Type '(variable: string, line: number) => string | null | undefined' is not assignable to type '(variable: string, line: number) => string'.
      Type 'string | null | undefined' is not assignable to type 'string'.
        Type 'undefined' is not assignable to type 'string'.

[rcjsuen]

@robcresswell Thank you for your bug report. Which version of TypeScript are you on?

[robcresswell]

I tried several: 3.1.6, 2.9.2, 2.8.4

[robcresswell]

If I can help out further, I'd love to; this lib looks excellent so far.

[rcjsuen]

@robcresswell I'm pretty sure I know what the problem is. However, I'm unable to reproduce the problem. I removed my package-lock.json file and changed my package.json to point to your versions but did not get a compiler error while building the library or running npm test.

dockerfile-ast/package.json

Line 35 in 0212961

"typescript": "~2.6.1",

Perhaps my tsconfig.json file is not strict enough?

[rcjsuen]

Never mind, using "strict": true did the trick. :)

[robcresswell]

Ah! Nice debugging. I was trying things locally to try and get some more concrete info before I got back to you. How should we proceed from here? Would you be willing to adopt a stricter tsconfig, or would you prefer me to relax mine?

[rcjsuen]

@robcresswell Thank you for your bug report. I have fixed this in `master. You can review the fix by looking at 7073209 if you wish.

To get around this for yourself in the immediate future, you can turn on skipLibCheck so that the TypeScript compiler doesn't try to check your dependent libraries.

[robcresswell]

That's awesome. Thanks for your help; any plans for an upcoming release?

[rcjsuen]

@robcresswell Not at the moment.

I think what I'd like to do is turn on strict and try to correct what it finds and then maybe cut a new release then. How does that sound to you?

[robcresswell]

Sounds great; if you'd like some help, please let me know. I know asking for changes in OSS can be a massive pain, so I don't want to demand your time by any means.

[rcjsuen]

@robcresswell No worries. You've already helped out by opening a bug. You're the first person to open a bug in this project. The other 45 before you were all opened by me! :)

If you have any suggestions, find something is unclear, or find another bug, let me know! The parsing of quoted strings, JSON, and ARG and ENV instructions are probably the most confusing but I imagine you won't be hitting those strange edge cases hopefully...

[rcjsuen]

Hi, @robcresswell. I just published a new version of dockerfile-ast to npm. I did not fix all of the null cases though so you may still need that skipLibCheck in your tsconfig.json file.

Thank you for your patience and understanding!