From 6c9abfa9789608f9b1ec0129fe08f51b91aa3b2b Mon Sep 17 00:00:00 2001
From: Heath Stewart <heaths@microsoft.com>
Date: Tue, 14 Mar 2017 16:30:51 -0700
Subject: [PATCH] Correctly sort legacy instances if no setup helper

Fixes issue #40 and adds tests to make sure we lexigraphically sort installationVersion when the ISetupHelper is not available (since as no VS2017 or newer instances available).
---
 docker/Tests/legacy.tests.ps1        | 35 ++++++++++++++++++++++++++++
 src/vswhere.lib/InstanceSelector.cpp |  7 +++++-
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/docker/Tests/legacy.tests.ps1 b/docker/Tests/legacy.tests.ps1
index 038513f..1a0de2f 100644
--- a/docker/Tests/legacy.tests.ps1
+++ b/docker/Tests/legacy.tests.ps1
@@ -51,4 +51,39 @@ Describe 'vswhere -legacy' {
             $instances.Count | Should Be 2
         }
     }
+
+    Context 'no instances' {
+        BeforeEach {
+             New-Item HKLM:\Software\WOW6432Node\Microsoft\VisualStudio\SxS\VS7 -Force | ForEach-Object {
+                 foreach ($version in '10.0', '14.0') {
+                     $_ | New-ItemProperty -Name $version -Value "C:\VisualStudio\$version" -Force
+                 }
+             }
+
+             Start-Process -Wait -FilePath C:\Windows\SysWOW64\regsvr32.exe -ArgumentList @(
+                 '/s',
+                 '/u',
+                 'C:\Downloads\Microsoft.VisualStudio.Setup.Configuration.Native\tools\x86\Microsoft.VisualStudio.Setup.Configuration.Native.dll'
+             )
+        }
+
+        AfterEach {
+             Start-Process -Wait -FilePath C:\Windows\SysWOW64\regsvr32.exe -ArgumentList @(
+                 '/s',
+                 'C:\Downloads\Microsoft.VisualStudio.Setup.Configuration.Native\tools\x86\Microsoft.VisualStudio.Setup.Configuration.Native.dll'
+             )
+        }
+
+        It 'returns 2 instances' {
+            $instances = C:\bin\vswhere.exe -legacy -format json | ConvertFrom-Json
+            $instances.Count | Should Be 2
+        }
+
+        It '-latest returns latest instance' {
+            $instances = C:\bin\vswhere.exe -legacy -latest -format json | ConvertFrom-Json
+            $instances.Count | Should Be 1
+            $instances[0].instanceId | Should Be 'VisualStudio.14.0'
+            $instances[0].installationPath | Should Be 'C:\VisualStudio\14.0'
+        }
+    }
 }
diff --git a/src/vswhere.lib/InstanceSelector.cpp b/src/vswhere.lib/InstanceSelector.cpp
index 0719cb8..450ebf1 100644
--- a/src/vswhere.lib/InstanceSelector.cpp
+++ b/src/vswhere.lib/InstanceSelector.cpp
@@ -33,7 +33,6 @@ InstanceSelector::InstanceSelector(_In_ const CommandArgs& args, _In_ ILegacyPro
 
 bool InstanceSelector::Less(const ISetupInstancePtr& a, const ISetupInstancePtr&  b) const
 {
-    static ci_equal equal;
     static ci_less less;
 
     bstr_t bstrVersionA, bstrVersionB;
@@ -62,6 +61,12 @@ bool InstanceSelector::Less(const ISetupInstancePtr& a, const ISetupInstancePtr&
                 return SUCCEEDED(hrB);
             }
         }
+        else
+        {
+            // If ISetupHelper is not available we have only legacy products, or very early pre-releases of VS2017.
+            // For version 10.0 and newer either should lexigraphically sort correctly.
+            return less(wstring(bstrVersionA), wstring(bstrVersionB));
+        }
     }
     else
     {