Implement the spread ... operator, other new functions, and indices on lambdas

[anthony-c-martin]

Adds the spread operator ... as well as various new functions + indexes on lambdas:

1. Spread operator - usage is as follows:
   • In an object:

     var objA = { bar: 'bar' }
     var objB = { foo: 'foo', ...objA } // equivalent to { foo: 'foo', bar: 'bar' }

   • In an array:

     var arrA = [ 2, 3 ]
     var arrB = [ 1, ...arrA, 4 ] // equivalent to [ 1, 2, 3, 4 ]

2. New functions + usage:
   • objectKeys: Returns the keys of an object parameter:

     var example = objectKeys({ a: 1, b: 2 }) // returns [ 'a', 'b' ]

   • mapValues: Create an object from an input object, using a custom lambda to map values:

     var example = mapValues({ foo: 'foo' }, val => toUpper(val)) // returns { foo: 'FOO' }

   • groupBy: Create an object with array values from an array, using a grouping condition:

     var example = groupBy(['foo', 'bar', 'baz'], x => substring(x, 0, 1)) // returns { f: [ 'foo' ], b: [ 'bar', 'baz' ]

   • shallowMerge: Perform a shallow merge of input object parameters:

     var example = shallowMerge([{ foo: 'foo' }, { bar: 'bar' }]) // returns { foo: 'foo', bar: 'bar' }

3. Optional indices on lambdas + usage:
   • map:

     var example = map(['a', 'b'], (x, i) => { index: i, val: x }) // returns [ { index: 0, val: 'a' }, { index: 1 val: 'b' } ]

   • reduce:

     var example = reduce([ 2, 3, 7 ], 0, (cur, next, i) => (i % 2 == 0) ? cur + next : cur) // returns 9

   • filter:

     var example = filter([ 'foo', 'bar', 'baz' ], (val, i) => i < 2 && substring(val, 0, 1) == 'b') // returns [ 'bar' ]

Closes #13560
Closes #9244
Closes #1560
Addresses some of the issues described under the following: #2082, #1853, #387

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 8808567201)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 8808567201

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 8808567201"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 8808567201

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 8808567201"

[github-actions]

Test Results

    66 files   -     33      66 suites   - 33   23m 20s ⏱️ - 15m 18s
10 868 tests  -      5  10 867 ✅  -      5  1 💤 ±0  0 ❌ ±0 
25 632 runs   - 12 767  25 630 ✅  - 12 766  2 💤  - 1  0 ❌ ±0 

Results for commit 880e364. ± Comparison against base commit 959dbbb.

♻️ This comment has been updated with latest results.

[shenglol]

[BernieWhite]

@anthony-c-martin Is the syntax example of reduce above correct?

var example = reduce([ 2, 3, 7 ], (cur, next, i) => (i % 2 == 0) ? cur + next : cur) // returns 9

When testing this locally, I'm getting a syntax issue with the required initialValue argument missing.

[anthony-c-martin]

@anthony-c-martin Is the syntax example of reduce above correct?

var example = reduce([ 2, 3, 7 ], (cur, next, i) => (i % 2 == 0) ? cur + next : cur) // returns 9

When testing this locally, I'm getting a syntax issue with the required initialValue argument missing.

Oops, this should be:

var example = reduce([ 2, 3, 7 ], 0, (cur, next, i) => (i % 2 == 0) ? cur + next : cur) // returns 9

I've updated the original comment.

[slavizh]

@anthony-c-martin I could not find the documentation for the new function features published yet but there are examples here in this PR. However for one of the main reasons to have index for lambda functions was to be able to access resource arrays and I have found out that this is not possible. Any idea why this was not done? It seems only half of the job was done.

properties: {
      actionGroups: map(eventSubscription.destination.actionGroups, (actionGroup, i) => actionGroups[i].id)
    }

shows error:

Using lambda variables inside resource or module array access is not currently supported. Found the following lambda variable(s) being accessed: "i".bicep(BCP247)

[anthony-c-martin]

@slavizh I've raised #14106 - will explain more there.