JsonPeek 1.2.0

Read values from JSON using JSONPath.

Usage:

  <JsonPeek ContentPath="[JSON_FILE]" Query="[JSONPath]">
    <Output TaskParameter="Result" PropertyName="Value" />
  </JsonPeek>
  <JsonPeek Content="[JSON]" Query="[JSONPath]">
    <Output TaskParameter="Result" ItemName="Values" />
  </JsonPeek>

Parameters:

You can either provide the path to a JSON file via ContentPath or provide the straight JSON content to Content. The Query is a JSONPath expression that is evaluated and returned via the Result task parameter. You can assign the resulting value to either a property (i.e. for a single value) or an item name (i.e. for multiple results).

JSON object properties are automatically projected as item metadata when assigning the resulting value to an item. For example, given the following JSON:

{
    "http": {
        "host": "localhost",
        "port": 80,
        "ssl": true
    }
}

You can read the entire http value as an item with each property as a metadata value with:

<JsonPeek ContentPath="host.json" Query="$.http">
    <Output TaskParameter="Result" ItemName="Http" />
</JsonPeek>

The Http item will have the following values (if it were declared in MSBuild):

<ItemGroup>
    <Http Include="[item raw json]">
        <host>localhost</host>
        <port>80</port>
        <ssl>true</ssl>
    </Http>
</ItemGroup>

These item metadata values could be read as MSBuild properties as follows, for example:

<PropertyGroup>
    <Host>@(Http -> '%(host)')</Host>
    <Port>@(Http -> '%(port)')</Port>
    <Ssl>@(Http -> '%(ssl)')</Ssl>
</PropertyGroup>

In addition to the explicitly opted in object properties, the entire node is available as raw JSON via the special _ (single underscore) metadata item.

If the matched value is empty, no items (because items cannot be constructed with empty identity) or property value will be returned. This makes it difficult to distinguish a successfully matched empty value from no value matched at all. For these cases, it's possible to specify an Empty value to stand-in for an empty (but successful) matched result instead, which allow to distinguish both scenarios:

<JsonPeek Content="$(Json)" Empty="$empty" Query="$(Query)">
  <Output TaskParameter="Result" PropertyName="Value" />
</JsonPeek>

<Error Condition="'$(Value)' == '$empty'" Text="The element $(Query) cannot have an empty value." />

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