Upgrade to typescript 3.9

[Brian Lewis]

As per discussion… should be trying to get more assistance from strongly typed code; and upgrading will get the codebase closer to Angular 9.

Also keen to get the “optional chaining” feature of 3.7 which will make a lot of code look cleaner.

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First step is to ascertain how much will break.

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[Brian Lewis]

Two things steps are required to update typescript - and this is becuase of the non-stndard ( ie old) structure of our project which gets compiled from grunt:

1. to change the compiler that actually does the compiling: update the version of typescript in packages.json in pineapples.client
2. to change the version that provides intellisense in the editor:

go to the VS Package Manager console, and install typescript from there:

npm install -g typescript@3.7.5

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[Brian Lewis]

In Visual Studio Package Manager console:

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[Brian Lewis]

A small number of compile errors were found going from 3.4.1 => 3.7.5. All ultimately related to lodash _.find

No other compile errors going from 3.7.5 => 3.9.3

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[Brian Lewis]

Added two small examples of “optional chaining” available from typescript 3.7 ff. Good to be aware of this , can save a bit of awkward code.

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public $onChanges(changes) {
            // isFirstChange() returns true when the bindings are first initialised PRIOR to onInit
            // better to ignore those
            if (changes.dashboard?.isFirstChange()) {
                return;
            }

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[Brian Lewis]

example of typescript optional chaining - now available

Resolves #861

→ <<cset bc7e2a6eca46>>