Add extension namespace functions

[levimatheri]

Description

• Added support for extension namespace functions
  • Enabled extension keyword in bicepparam files
  • Updated external input function emit to work with LanguageExpression. This is because the extension namespace function may define the expression that it should be reduced to which may not necessarily be the same as the function syntax.
  • Updated external input baselines to fix duplicate external input definitions generated by the same syntax.

Example Usage

Namespace function definition:

{
  "$type": "NamespaceFunctionType",
  "name": "config",
  "description": "Reads configuration from external tooling",
  "evaluatedLanguageExpression": "[externalInput('ext.expression', concat('$config(', parameters('configKey'), ')'))]",
  "parameters": [
    {
      "name": "configKey",
      "type": {
        "$ref": "#/0" // StringType
      },
      "description": "The configuration key parameter",
      "flags": 3 // Required | CompileTimeConstant
    }
  ],
  "outputType": {
    "$ref": "#/3" // AnyType
  },
  "visibleInFileKind": 2 // bicepparam
}

Bicepparam:

using none
extension ext
param redisConfig = json(ext.config('redis'))

Compiled json:

{
  "parameters": {
    "redisConfig": {
      "expression": "[json(externalInputs('ext_expression_0'))]"
    }
  },
  "externalInputDefinitions": {
    "ext_expression_0": {
      "kind": "ext.expression",
      "config": "$config(redis)"
    }
  }
}

Checklist

• I have read and adhere to the contribution guide.

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 21645183295)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 21645183295

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 21645183295"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 21645183295

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 21645183295"

[jeskew]

[Nit]: With """ blocks, multiline snippets don't have to be flush with the left margin. I try to keep them bounded by one indentation level past the line they appear in, but opinions on what's most readable vary.

[jeskew]

Is there any way to make this more specific? What exceptions are expected here?

[levimatheri]

Added handling and unit test for ExpressionException if there is a failure running the arm expression evaluator.

[jeskew]

Is NameEquals case insensitive?

[levimatheri]

Yes, it's case-insensitive.

bicep/src/Bicep.Core/Extensions/LanguageExpressionExtensions.cs

Lines 9 to 10 in c378ace

	public static bool NameEquals(this FunctionExpression expression, string name)
	=> StringComparer.OrdinalIgnoreCase.Equals(expression.Function, name);

[jeskew]

Could you add a couple of tests here? I think there should be tests covering:

1. The result of one namespace function being passed as an argument to another.
2. A namespace function where externalInput is part of a function property

[levimatheri]

Added