Allow specifying a replacement value for empty results

This allows distinguishing a non-matching query vs a matched value that is actually empty. Fixed #7
devlooped · Sep 30, 2021 · 2ca7cc1 · 2ca7cc1
1 parent cc949d6
commit 2ca7cc1
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Showing 6 changed files with 107 additions and 3 deletions.
diff --git a/Devlooped.Json.sln b/Devlooped.Json.sln
@@ -12,6 +12,8 @@ EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{58AD3669-734C-4A6F-B622-9F75D7E903C2}"
 	ProjectSection(SolutionItems) = preProject
 		.editorconfig = .editorconfig
+		.netconfig = .netconfig
+		.github\dependabot.yml = .github\dependabot.yml
 		readme.md = readme.md
 	EndProjectSection
 EndProject

diff --git a/readme.md b/readme.md
@@ -27,8 +27,9 @@ Parameters:
 
 | Parameter   | Description                                                                                                    |
 | ----------- | -------------------------------------------------------------------------------------------------------------- |
-| Content     | Optional `string` parameter. Input/Output.<br/>Specifies the JSON input as a string.                           |
+| Content     | Optional `string` parameter.<br/>Specifies the JSON input as a string.                                         |
 | ContentPath | Optional `ITaskItem` parameter.<br/>Specifies the JSON input as a file path.                                   |
+| Empty       | Optional `string` parameter.<br/>Value to use as a replacement for empty values matched in JSON.               |
 | Query       | Required `string` parameter.<br/>Specifies the [JSONPath](https://goessner.net/articles/JsonPath/) expression. |
 | Result      | Output `ITaskItem[]` parameter.<br/>Contains the results that are returned by the task.                        |
 
@@ -86,6 +87,21 @@ These item metadata values could be read as MSBuild properties as follows, for e
 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:
+
+```xml
+<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." />
+```
+
+
 ![JsonPoke Icon](assets/img/jsonpoke.png) JsonPoke
 ============
 

diff --git a/src/JsonPeek/JsonPeek.cs b/src/JsonPeek/JsonPeek.cs
@@ -19,6 +19,14 @@ public class JsonPeek : Task
     /// </summary>
     public ITaskItem? ContentPath { get; set; }
 
+    /// <summary>
+    /// Specifies an optional value to use as a replacement for 
+    /// empty values matched in JSON. This allows distinguishing 
+    /// non-matching queries versus queries that match nodes but 
+    /// contain an empty value.
+    /// </summary>
+    public string? Empty { get; set; }
+
     /// <summary>
     /// Specifies the JSONPath query.
     /// </summary>
@@ -57,6 +65,7 @@ public override bool Execute()
         Result = json.SelectTokens(Query)
             // NOTE: we cannot create items with empty ItemSpec, so skip them entirely.
             // see https://github.com/dotnet/msbuild/issues/3399
+            .Select(x => !string.IsNullOrEmpty(x.ToString()) ? x : Empty)
             .Where(x => !string.IsNullOrEmpty(x.ToString()))
             .SelectMany(x => x.AsItems()).ToArray();
 

diff --git a/src/JsonPeek/readme.md b/src/JsonPeek/readme.md
@@ -1,7 +1,6 @@
 [![Version](https://img.shields.io/nuget/vpre/JsonPeek.svg?color=royalblue)](https://www.nuget.org/packages/JsonPeek)
 [![Downloads](https://img.shields.io/nuget/dt/JsonPeek.svg?color=green)](https://www.nuget.org/packages/JsonPeek)
 [![License](https://img.shields.io/github/license/devlooped/json.svg?color=blue)](https://github.com/devlooped/json/blob/main/license.txt)
-[![Build](https://github.com/devlooped/json/workflows/build/badge.svg?branch=main)](https://github.com/devlooped/json/actions)
 
 Usage:
 
@@ -68,12 +67,27 @@ These item metadata values could be read as MSBuild properties as follows, for e
 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:
+
+```xml
+<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." />
+```
+
 ## Parameters
 
 | Parameter   | Description                                                                                                    |
 | ----------- | -------------------------------------------------------------------------------------------------------------- |
 | Content     | Optional `string` parameter.<br/>Specifies the JSON input as a string.                                         |
 | ContentPath | Optional `ITaskItem` parameter.<br/>Specifies the JSON input as a file path.                                   |
+| Empty       | Optional `string` parameter.<br/>Value to use as a replacement for empty values matched in JSON.               |
 | Query       | Required `string` parameter.<br/>Specifies the [JSONPath](https://goessner.net/articles/JsonPath/) expression. |
 | Result      | Output `ITaskItem[]` parameter.<br/>Contains the results that are returned by the task.                        |
 

diff --git a/src/JsonPoke/readme.md b/src/JsonPoke/readme.md
@@ -1,7 +1,6 @@
 [![Version](https://img.shields.io/nuget/vpre/JsonPoke.svg?color=royalblue)](https://www.nuget.org/packages/JsonPoke)
 [![Downloads](https://img.shields.io/nuget/dt/JsonPoke.svg?color=green)](https://www.nuget.org/packages/JsonPoke)
 [![License](https://img.shields.io/github/license/devlooped/json.svg?color=blue)](https://github.com/devlooped/json/blob/main/license.txt)
-[![Build](https://github.com/devlooped/json/workflows/build/badge.svg?branch=main)](https://github.com/devlooped/json/actions)
 
 Usage:
 

diff --git a/src/Tests/Peek.targets b/src/Tests/Peek.targets
@@ -38,6 +38,70 @@
     <Error Condition="'$(Expected)' != '$(Actual)'" Text="Expected $(Expected) but was $(Actual)" />
   </Target>
 
+  <Target Name="PeekEmptyValue">
+    <PropertyGroup>
+      <Json>
+        {
+          "hello": ""
+        }
+      </Json>
+      <Query>$.hello</Query>
+      <Expected></Expected>
+    </PropertyGroup>
+
+    <JsonPeek Content="$(Json)" Query="$(Query)">
+      <Output TaskParameter="Result" PropertyName="Actual" />
+    </JsonPeek>
+
+    <JsonPeek Content="$(Json)" Query="$(Query)">
+      <Output TaskParameter="Result" ItemName="Actual" />
+    </JsonPeek>
+
+    <Error Condition="'$(Expected)' != '$(Actual)'" Text="Expected $(Expected) but was $(Actual)" />
+    <Error Condition="@(Actual -> Count()) != 0" Text="Expected @(Actual) to be empty" />
+  </Target>
+
+  <Target Name="PeekEmptyNonDefaultValue">
+    <PropertyGroup>
+      <Json>
+        {
+        "hello": ""
+        }
+      </Json>
+      <Query>$.hello</Query>
+      <Expected>$empty</Expected>
+    </PropertyGroup>
+
+    <JsonPeek Content="$(Json)" Empty="$empty" Query="$(Query)">
+      <Output TaskParameter="Result" PropertyName="Actual" />
+    </JsonPeek>
+
+    <JsonPeek Content="$(Json)" Empty="$empty" Query="$(Query)">
+      <Output TaskParameter="Result" ItemName="Actual" />
+    </JsonPeek>
+
+    <Error Condition="'$(Expected)' != '$(Actual)'" Text="Expected $(Expected) but was $(Actual)" />
+    <Error Condition="@(Actual -> Count()) != 1" Text="Expected @(Actual) to have one item" />
+  </Target>
+
+  <Target Name="PeekNotFoundNonDefaultValue">
+    <PropertyGroup>
+      <Json>
+        {
+        "hello": ""
+        }
+      </Json>
+      <Query>$.foo</Query>
+      <Expected></Expected>
+    </PropertyGroup>
+
+    <JsonPeek Content="$(Json)" Empty="$empty" Query="$(Query)">
+      <Output TaskParameter="Result" PropertyName="Actual" />
+    </JsonPeek>
+
+    <Error Condition="'$(Expected)' != '$(Actual)'" Text="Expected $(Expected) but was $(Actual)" />
+  </Target>
+
   <Target Name="PeekFileValues">
     <JsonPeek ContentPath="sample.json" Query="$.immutable">
       <Output TaskParameter="Result" PropertyName="Actual" />