Make ConvertFrom-Json deserialize an array of objects with multiple lines. (#3823)

* Fixing ConvertFrom-Json on CoreCLR to be able to handle a collection of strings which represent a JSON content.

* Adding test case for ConvertFrom-Json to process an array of PSObjects as a single string.

src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/ConvertFromJsonCommand.cs

@@ -72,8 +72,8 @@ namespace Microsoft.PowerShell.Commands
         protected override void EndProcessing()
         {
             // When Input is provided through pipeline, the input can be represented in the following two ways:
-            // 1. Each input to the buffer is a complete Json content. There can be multiple inputs of this format.
-            // 2. The complete buffer input collectively represent a single JSon format. This is typically the majority of the case.
+            // 1. Each input in the collection is a complete Json content. There can be multiple inputs of this format.
+            // 2. The complete input is a collection which represents a single Json content. This is typically the majority of the case.
             if (_inputObjectBuffer.Count > 0)
             {
                 if (_inputObjectBuffer.Count == 1)
@@ -85,6 +85,7 @@ namespace Microsoft.PowerShell.Commands
                     bool successfullyConverted = false;
                     try
                     {
+                        // Try to deserialize the first element.
                         successfullyConverted = ConvertFromJsonHelper(_inputObjectBuffer[0]);
                     }
                     catch (ArgumentException)
@@ -102,6 +103,7 @@ namespace Microsoft.PowerShell.Commands
                     }
                     else
                     {
+                        // Process the entire input as a single Json content.
                         ConvertFromJsonHelper(string.Join(System.Environment.NewLine, _inputObjectBuffer.ToArray()));
                     }
                 }

src/Microsoft.PowerShell.Commands.Utility/commands/utility/WebCmdlet/JsonObject.cs

@@ -7,6 +7,7 @@ using System.Collections.Generic;
 using System.Globalization;
 using System.Diagnostics.CodeAnalysis;
 using System.Management.Automation;
+using System.Text.RegularExpressions;
 #if CORECLR
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
@@ -42,11 +43,28 @@ namespace Microsoft.PowerShell.Commands
             {
                 throw new ArgumentNullException("input");
             }
+
             error = null;
 #if CORECLR
             object obj = null;
             try
             {
+                // JsonConvert.DeserializeObject does not throw an exception when an invalid Json array is passed.
+                // This issue is being tracked by https://github.com/JamesNK/Newtonsoft.Json/issues/1321.
+                // To work around this, we need to identify when input is a Json array, and then try to parse it via JArray.Parse().
+
+                // If input starts with '[' or ends with ']' (ignoring white spaces).
+                if ((Regex.Match(input, @"(^\s*\[)|(\s*\]$)")).Success)
+                {
+                    // JArray.Parse() will throw a JsonException if the array is invalid.
+                    // This will be caught by the catch block below, and then throw an
+                    // ArgumentException - this is done to have same behavior as the JavaScriptSerializer.
+                    JArray.Parse(input);
+
+                    // Please note that if the Json array is valid, we don't do anything,
+                    // we just continue the deserialization.
+                }
+
                 obj = JsonConvert.DeserializeObject(input, new JsonSerializerSettings() { TypeNameHandling = TypeNameHandling.None, MaxDepth = 1024 });
 
                 // JObject is a IDictionary

test/powershell/Modules/Microsoft.PowerShell.Utility/Pester.Commands.Cmdlets.Json.Tests.ps1

@@ -228,7 +228,6 @@ Describe "Json Tests" -Tags "Feature" {
 
             # add a ScriptProperty called IsOld which returns whether the version is an older version
             $versionObject | Add-Member -MemberType ScriptProperty -Name IsOld -Value { ($this.Major -le 3) }
-
             $jstr = ConvertTo-Json $versionObject
 
             # convert the JSON string to a JSON object
@@ -1455,4 +1454,25 @@ Describe "Json Bug fixes"  -Tags "Feature" {
     {
         RunJsonTest $testCase
     }
+
+    It "ConvertFrom-Json deserializes an array of PSObjects (in multiple lines) as a single string." {
+
+        # Create an array of PSCustomObjects, and serialize it
+        $array = [pscustomobject]@{ objectName = "object1Name"; objectValue = "object1Value" },
+                 [pscustomobject]@{ objectName = "object2Name"; objectValue = "object2Value" }
+
+        # Serialize the array to a text file
+        $filePath = Join-Path $TESTDRIVE test.json
+        $array | ConvertTo-Json | Out-File $filePath -Encoding utf8
+
+        # Read the object as an array of PSObjects and deserialize it.
+        $result = Get-Content $filePath | ConvertFrom-Json
+        $result.Count | Should be 2
+    }
+
+    It "ConvertFrom-Json deserializes an array of strings (in multiple lines) as a single string." {
+
+        $result = "[1,","2,","3]" | ConvertFrom-Json
+        $result.Count | Should be 3
+    }
 }