fix incorrect corrupted size message

src/dotnet-install.ps1

@@ -911,23 +911,32 @@ function DownloadFile($Source, [string]$OutPath) {
 function ValidateRemoteLocalFileSizes([string]$LocalFileOutPath, $SourceUri) {
     try {
         $remoteFileSize = Get-Remote-File-Size -zipUri $SourceUri
-        $fileSize = [long](Get-Item $LocalFileOutPath).Length
-        Say "Downloaded file $SourceUri size is $fileSize bytes."
-
-        if ((![string]::IsNullOrEmpty($remoteFileSize)) -and !([string]::IsNullOrEmpty($fileSize)) ) {
-            if ($remoteFileSize -ne $fileSize) {
-                Say "The remote and local file sizes are not equal. Remote file size is $remoteFileSize bytes and local size is $fileSize bytes. The local package may be corrupted."
-            }
-            else {
-                Say "The remote and local file sizes are equal."
-            }   
+        $localFileSize = $null
+
+        if (Test-Path $LocalFileOutPath) {
+            $localFileSize = [long](Get-Item $LocalFileOutPath).Length
+            Say "Downloaded file $SourceUri size is $localFileSize bytes."
+        }
+
+        if ($null -eq $localFileSize -or $localFileSize -le 0) {
+            Say "Local file size could not be measured. The package may be corrupted or missing."
+            return
+        }
+
+        if ([string]::IsNullOrEmpty($remoteFileSize)) {
+            Say-Verbose "Remote file size could not be determined. Skipping file size validation."
+            return
+        }
+
+        if ($remoteFileSize -ne $localFileSize) {
+            Say "The remote and local file sizes are not equal. Remote file size is $remoteFileSize bytes and local size is $localFileSize bytes. The local package may be corrupted."
         }
         else {
-            Say "Either downloaded or local package size can not be measured. One of them may be corrupted."
+            Say "The remote and local file sizes are equal."
         }
     }
     catch {
-        Say "Either downloaded or local package size can not be measured. One of them may be corrupted."
+        Say-Verbose "Unable to validate remote and local file sizes."
     }
 }
 

src/dotnet-install.sh

@@ -609,17 +609,16 @@ validate_remote_local_file_sizes()
     if [ -n "$file_size" ]; then
         say "Downloaded file size is $file_size bytes."
 
-        if [ -n "$remote_file_size" ] && [ -n "$file_size" ]; then
-            if [ "$remote_file_size" -ne "$file_size" ]; then
-                say "The remote and local file sizes are not equal. The remote file size is $remote_file_size bytes and the local size is $file_size bytes. The local package may be corrupted."
-            else
-                say "The remote and local file sizes are equal."
-            fi
+        if [ -z "$remote_file_size" ]; then
+            say_verbose "Remote file size could not be determined. Skipping file size validation."
+        elif [ "$remote_file_size" -ne "$file_size" ]; then
+            say "The remote and local file sizes are not equal. The remote file size is $remote_file_size bytes and the local size is $file_size bytes. The local package may be corrupted."
+        else
+            say "The remote and local file sizes are equal."
         fi
-
     else
-        say "Either downloaded or local package size can not be measured. One of them may be corrupted."      
-    fi 
+        say "Local file size could not be measured. The package may be corrupted or missing."
+    fi
 }
 
 # args:

tests/Install-Scripts.Test/ValidateFileSizeTests.cs

@@ -0,0 +1,189 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Diagnostics;
+using System.IO;
+using System.Runtime.InteropServices;
+using FluentAssertions;
+using Xunit;
+
+namespace Microsoft.DotNet.InstallationScript.Tests
+{
+    public class ValidateFileSizeTests : IDisposable
+    {
+        private readonly string _tempDir;
+
+        public ValidateFileSizeTests()
+        {
+            _tempDir = Path.Combine(Path.GetTempPath(), "InstallScript-FileSizeTests", Path.GetRandomFileName());
+            Directory.CreateDirectory(_tempDir);
+        }
+
+        public void Dispose()
+        {
+            try { Directory.Delete(_tempDir, true); }
+            catch (DirectoryNotFoundException) { }
+        }
+
+        [Fact]
+        public void WhenRemoteSizeIsUnavailable_ShouldNotWarnAboutCorruption()
+        {
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return;
+
+            var tempFile = CreateTempFileWithSize(1024);
+            var result = RunPowerShellValidation(tempFile, remoteFileSize: null);
+
+            result.StdOut.Should().Contain("Downloaded file");
+            result.StdOut.Should().Contain("1024 bytes");
+            result.StdOut.Should().NotContain("corrupted");
+            result.StdOut.Should().Contain("Skipping file size validation");
+        }
+
+        [Fact]
+        public void WhenFileSizesMatch_ShouldReportEqual()
+        {
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return;
+
+            var tempFile = CreateTempFileWithSize(2048);
+            var result = RunPowerShellValidation(tempFile, remoteFileSize: "2048");
+
+            result.StdOut.Should().Contain("remote and local file sizes are equal");
+            result.StdOut.Should().NotContain("corrupted");
+        }
+
+        [Fact]
+        public void WhenFileSizesDontMatch_ShouldWarnAboutCorruption()
+        {
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return;
+
+            var tempFile = CreateTempFileWithSize(1024);
+            var result = RunPowerShellValidation(tempFile, remoteFileSize: "9999");
+
+            result.StdOut.Should().Contain("remote and local file sizes are not equal");
+            result.StdOut.Should().Contain("may be corrupted");
+        }
+
+        [Fact]
+        public void WhenLocalFileIsMissing_ShouldWarnAboutCorruptionOrMissing()
+        {
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return;
+
+            var missingFile = Path.Combine(_tempDir, "does-not-exist.zip");
+            var result = RunPowerShellValidation(missingFile, remoteFileSize: "1024");
+
+            result.StdOut.Should().Contain("corrupted or missing");
+        }
+
+        [Fact]
+        public void WhenExceptionOccurs_ShouldNotWarnAboutCorruption()
+        {
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return;
+
+            // Inject a Get-Remote-File-Size that throws to exercise the catch block.
+            var tempFile = CreateTempFileWithSize(512);
+            string escapedPath = tempFile.Replace("'", "''");
+            string script = $@"
+function Say($str) {{ Write-Host ""dotnet-install: $str"" }}
+function Say-Verbose($str) {{ Write-Host ""dotnet-install: $str"" }}
+function Get-Remote-File-Size($zipUri) {{ throw 'Simulated network error' }}
+
+{GetValidateFunctionSource()}
+
+ValidateRemoteLocalFileSizes -LocalFileOutPath '{escapedPath}' -SourceUri 'https://example.com/test.zip'
+";
+
+            var result = RunPowerShellScript(script);
+
+            result.StdOut.Should().NotContain("One of them may be corrupted");
+            result.StdOut.Should().Contain("Unable to validate");
+        }
+
+        private string CreateTempFileWithSize(int sizeInBytes)
+        {
+            var filePath = Path.Combine(_tempDir, Path.GetRandomFileName());
+            File.WriteAllBytes(filePath, new byte[sizeInBytes]);
+            return filePath;
+        }
+
+        private (string StdOut, string StdErr, int ExitCode) RunPowerShellValidation(
+            string localFilePath,
+            string? remoteFileSize)
+        {
+            string mockRemoteReturn = remoteFileSize != null
+                ? $"return '{remoteFileSize}'"
+                : "return $null";
+
+            string escapedPath = localFilePath.Replace("'", "''");
+
+            string script = $@"
+function Say($str) {{ Write-Host ""dotnet-install: $str"" }}
+function Say-Verbose($str) {{ Write-Host ""dotnet-install: $str"" }}
+function Get-Remote-File-Size($zipUri) {{ {mockRemoteReturn} }}
+
+{GetValidateFunctionSource()}
+
+ValidateRemoteLocalFileSizes -LocalFileOutPath '{escapedPath}' -SourceUri 'https://example.com/test.zip'
+";
+            return RunPowerShellScript(script);
+        }
+
+        private static string GetValidateFunctionSource() => @"
+function ValidateRemoteLocalFileSizes([string]$LocalFileOutPath, $SourceUri) {
+    try {
+        $remoteFileSize = Get-Remote-File-Size -zipUri $SourceUri
+        $localFileSize = $null
+
+        if (Test-Path $LocalFileOutPath) {
+            $localFileSize = [long](Get-Item $LocalFileOutPath).Length
+            Say ""Downloaded file $SourceUri size is $localFileSize bytes.""
+        }
+
+        if ($null -eq $localFileSize -or $localFileSize -le 0) {
+            Say ""Local file size could not be measured. The package may be corrupted or missing.""
+            return
+        }
+
+        if ([string]::IsNullOrEmpty($remoteFileSize)) {
+            Say-Verbose ""Remote file size could not be determined. Skipping file size validation.""
+            return
+        }
+
+        if ($remoteFileSize -ne $localFileSize) {
+            Say ""The remote and local file sizes are not equal. Remote file size is $remoteFileSize bytes and local size is $localFileSize bytes. The local package may be corrupted.""
+        }
+        else {
+            Say ""The remote and local file sizes are equal.""
+        }
+    }
+    catch {
+        Say-Verbose ""Unable to validate remote and local file sizes.""
+    }
+}
+";
+
+        private static (string StdOut, string StdErr, int ExitCode) RunPowerShellScript(string script)
+        {
+            var startInfo = new ProcessStartInfo
+            {
+                FileName = "powershell.exe",
+                Arguments = "-ExecutionPolicy Bypass -NoProfile -NoLogo -Command -",
+                RedirectStandardInput = true,
+                RedirectStandardOutput = true,
+                RedirectStandardError = true,
+                UseShellExecute = false,
+                CreateNoWindow = true
+            };
+
+            using var process = new Process { StartInfo = startInfo };
+            process.Start();
+            process.StandardInput.Write(script);
+            process.StandardInput.Close();
+
+            string stdOut = process.StandardOutput.ReadToEnd();
+            string stdErr = process.StandardError.ReadToEnd();
+            process.WaitForExit();
+
+            return (stdOut, stdErr, process.ExitCode);
+        }
+    }
+}