Backward compatibility for validating JSON files using Test-JSON command (#78)

* Backward compatibility for validating JSON files using Test-JSON command.

    - Skip JSON validation if `Test-Json` command is not available, for backward compatibility (PowerShell 5.1).

    - Update README.md recommending PowerShell 7.0+ for best experience.

    - Throw an error is JSON validation fails

Author: TinaMor

README.md

@@ -32,6 +32,8 @@ You can find documentation for these functions here: [Containers-Toolkit Documen
 
 1. PowerShell: Minimum Version 7
 
+    > NOTE: While this module is developed and tested with PowerShell 7, it may work with PowerShell 5.1, but it is not guaranteed. PowerShell 7 is recommended for the best experience.
+
 1. `HNS` module
 
     To install the HNS module, follow the [instructions here](./docs/FAQs.md#2-new-hnsnetwork-command-does-not-exist)

Tests/CommonToolUtilities.Tests.ps1

@@ -534,6 +534,15 @@ Describe "CommonToolUtilities.psm1" {
                 -ParameterFilter { $Path -eq $Script:ChecksumFile }
         }
 
+        It "should skip JSON validation when Test-Json is not available" {
+            Mock Get-Command -ModuleName "CommonToolUtilities" -MockWith { return $null } -ParameterFilter {
+                $Name -eq 'Test-Json'
+            }
+
+            { & $Script:FunctionToCall } | Should -Not -Throw
+            Should -Invoke Test-Json -Times 0 -Scope It -ModuleName "CommonToolUtilities"
+        }
+
         It "should throw an error if checksum file does not exist" {
             Mock Test-Path -ModuleName "CommonToolUtilities" -MockWith { return $false } -ParameterFilter { $Path -eq $Script:ChecksumFile }
 
@@ -576,14 +585,24 @@ Describe "CommonToolUtilities.psm1" {
             { & $Script:FunctionToCall } | Should -Throw "Invalid schema file: $Script:SchemaFile. Schema file is empty."
         }
 
-        It "should throw an error if the JSON file is not valid" {
+        It "should throw an error if Test-Json fails" {
             Mock Get-Content -ModuleName "CommonToolUtilities" -MockWith { return "Test data" }
 
             # Test-Json returns true if the JSON is valid, otherwise it throws an error
             Mock Test-Json -ModuleName "CommonToolUtilities" -MockWith { Throw "Error" }
 
             # Test the function
-            { & $Script:FunctionToCall } | Should -Throw "Invalid JSON format in checksum file. Error"
+            { & $Script:FunctionToCall } | Should -Throw "Error validating JSON checksum file. Error"
+        }
+
+        It "should throw an error if the JSON file is not valid" {
+            Mock Get-Content -ModuleName "CommonToolUtilities" -MockWith { return "Test data" }
+
+            # Test-Json returns true if the JSON is valid, otherwise it throws an error
+            Mock Test-Json -ModuleName "CommonToolUtilities" -MockWith { return $false }
+
+            # Test the function
+            { & $Script:FunctionToCall } | Should -Throw "Checksum file validation failed for $Script:ChecksumFile. Please check the file format and schema."
         }
 
         It "should throw an error if script block throws an error" {

containers-toolkit/Private/CommonToolUtilities.psm1

@@ -67,8 +67,8 @@ public enum ActionConsent {
 }
 '@
 
-$HASH_FUNCTIONS = @("SHA1", "SHA256", "SHA384", "SHA512", "MD5")
-$HASH_FUNCTIONS_STR = $HASH_FUNCTIONS -join '|' # SHA1|SHA256|SHA384|SHA512|MD5
+$HASH_FUNCTIONS = @("SHA256", "SHA384", "SHA512")
+$HASH_FUNCTIONS_STR = $HASH_FUNCTIONS -join '|' # SHA256|SHA384|SHA512
 $NERDCTL_CHECKSUM_FILE_PATTERN = "(?<hashfunction>(?:^({0})))" -f ($HASH_FUNCTIONS -join '|')
 $NERDCTL_FILTER_SCRIPTBLOCK_STR = { (("{0}" -match "$NERDCTL_CHECKSUM_FILE_PATTERN") -and "{0}" -notmatch ".*.asc$") }.ToString()
 
@@ -579,6 +579,9 @@ function Test-JSONChecksum {
     # Validate the checksum file
     $isJsonValid = ValidateJSONChecksumFile -ChecksumFilePath $checksumFile -SchemaFile $SchemaFile
     Write-Debug "Checksum JSON file validation status. {success: $isJsonValid}"
+    if ($isJsonValid -eq $false) {
+        Throw "Checksum file validation failed for $checksumFile. Please check the file format and schema."
+    }
 
     if ($null -eq $ExtractDigestScriptBlock) {
         Write-Debug "Using default JSON checksum extraction script block"
@@ -650,11 +653,16 @@ function ValidateJSONChecksumFile {
 
     # Test JSON checksum file is valid
     try {
+        # Check if Test-Json cmdlet is available
+        if (-not (Get-Command -Name Test-Json -ErrorAction SilentlyContinue)) {
+            Write-Warning "Couldn't validate JSON checksum file. Test-Json cmdlet is not available. Upgrade to PowerShell 6.1 or later to use this feature."
+            return $null
+        }
         $isValidJSON = Test-Json -Json "$(Get-Content -Path $ChecksumFilePath -Raw)" -Schema "$schemaFileContent"
         return $isValidJSON
     }
     catch {
-        Throw "Invalid JSON format in checksum file. $_"
+        Throw "Error validating JSON checksum file. $($_.Exception.Message)"
     }
 }