fix(cli): harden tht installer replacement

scripts/install-tht.ps1

@@ -37,6 +37,40 @@ function Add-InstallDirectoryToUserPath([string]$InstallDirectory) {
     return $true
 }
 
+function Replace-InstalledBinary([string]$StagedBinary, [string]$TargetBinary) {
+    $backupBinary = $null
+    $replacedExistingBinary = $false
+    try {
+        if (Test-Path -LiteralPath $TargetBinary -PathType Leaf) {
+            $backupBinary = Join-Path (Split-Path -Parent $TargetBinary) ('.tht-previous-' + [guid]::NewGuid() + '.exe')
+            [System.IO.File]::Replace($StagedBinary, $TargetBinary, $backupBinary, $true)
+            $replacedExistingBinary = $true
+        } else {
+            [System.IO.File]::Move($StagedBinary, $TargetBinary)
+        }
+
+        & $TargetBinary --help | Out-Null
+        if ($LASTEXITCODE -ne 0) { throw 'installed tht did not pass its help check' }
+
+        if ($backupBinary -and (Test-Path -LiteralPath $backupBinary -PathType Leaf)) {
+            Remove-Item -LiteralPath $backupBinary -Force -ErrorAction Stop
+        }
+    } catch {
+        $installFailure = $_
+        if ($replacedExistingBinary -and $backupBinary -and (Test-Path -LiteralPath $backupBinary -PathType Leaf)) {
+            try {
+                [System.IO.File]::Replace($backupBinary, $TargetBinary, $null, $true)
+                $backupBinary = $null
+            } catch {
+                throw "tht replacement failed; the previous executable remains at $backupBinary. Original failure: $installFailure. Restore failure: $_"
+            }
+        }
+        throw $installFailure
+    } finally {
+        Remove-Item -LiteralPath $StagedBinary -Force -ErrorAction SilentlyContinue
+    }
+}
+
 $repositoryRoot = Split-Path -Parent $PSScriptRoot
 $buildOutput = $null
 $sourceArtifactForInstall = $null
@@ -86,9 +120,8 @@ try {
     Copy-Item -LiteralPath $sourceArtifactForInstall -Destination $stagedBinary -Force
     & $stagedBinary --help | Out-Null
     if ($LASTEXITCODE -ne 0) { throw 'native artifact did not pass its help check' }
-    Move-Item -LiteralPath $stagedBinary -Destination (Join-Path $installDirectory 'tht.exe') -Force
+    Replace-InstalledBinary $stagedBinary (Join-Path $installDirectory 'tht.exe')
 } finally {
-    Remove-Item -LiteralPath $stagedBinary -Force -ErrorAction SilentlyContinue
     if ($buildOutput) { Remove-Item -LiteralPath $buildOutput -Recurse -Force -ErrorAction SilentlyContinue }
 }
 

scripts/install-tht.sh

@@ -43,7 +43,9 @@ validate_packaged_artifact() {
   expected=${THT_BUILD_ARTIFACT_SHA256:-}
   [[ "$expected" =~ ^[[:xdigit:]]{64}$ ]] || fail "THT_BUILD_ARTIFACT_SHA256 must be a 64-character SHA-256 digest"
   actual=$(sha256 "$artifact")
-  [[ "${actual,,}" == "${expected,,}" ]] || fail "packaged tht artifact checksum does not match"
+  actual=$(printf '%s' "$actual" | tr '[:upper:]' '[:lower:]')
+  expected=$(printf '%s' "$expected" | tr '[:upper:]' '[:lower:]')
+  [[ "$actual" == "$expected" ]] || fail "packaged tht artifact checksum does not match"
 }
 
 build_artifact() {

scripts/test-install-tht.ps1

@@ -9,7 +9,7 @@ if (-not (Test-Path -LiteralPath $installer)) {
 $isWindowsHost = $env:OS -eq 'Windows_NT'
 if (-not $isWindowsHost) {
     $installerText = Get-Content -LiteralPath $installer -Raw
-    foreach ($requiredText in @('THT_INSTALL_DIRECTORY', 'LOCALAPPDATA', 'SetEnvironmentVariable', 'build-tht.sh', 'Move-Item')) {
+    foreach ($requiredText in @('THT_INSTALL_DIRECTORY', 'LOCALAPPDATA', 'SetEnvironmentVariable', 'build-tht.sh', 'File]::Replace')) {
         if (-not $installerText.Contains($requiredText)) {
             throw "Windows installer is missing required behavior: $requiredText"
         }
@@ -20,37 +20,57 @@ if (-not $isWindowsHost) {
 
 $temporaryRoot = Join-Path ([System.IO.Path]::GetTempPath()) ("tht installer test {0}" -f [guid]::NewGuid())
 $installDirectory = Join-Path $temporaryRoot 'command directory'
-$artifact = Join-Path $temporaryRoot 'tht.exe'
+$artifactOne = Join-Path $temporaryRoot 'tht-one.exe'
+$artifactTwo = Join-Path $temporaryRoot 'tht-two.exe'
+$brokenArtifact = Join-Path $temporaryRoot 'tht-broken.exe'
 $userPathStore = Join-Path $temporaryRoot 'user-path.txt'
 New-Item -ItemType Directory -Path $temporaryRoot -Force | Out-Null
 try {
-    $program = @'
+    $programOne = @'
 using System;
-public static class Program {
+public static class ProgramOne {
     public static void Main(string[] args) {
         if (args.Length == 1 && args[0] == "--help") { Console.WriteLine("Usage: tht"); return; }
-        if (args.Length == 1 && args[0] == "version") { Console.WriteLine("tht test version"); return; }
+        if (args.Length == 1 && args[0] == "version") { Console.WriteLine("tht test version one"); return; }
         Environment.Exit(2);
     }
 }
 '@
-    Add-Type -TypeDefinition $program -OutputAssembly $artifact -OutputType ConsoleApplication
+    $programTwo = $programOne.Replace('ProgramOne', 'ProgramTwo').Replace('tht test version one', 'tht test version two')
+    $brokenProgram = $programOne.Replace('ProgramOne', 'BrokenProgram').Replace('Console.WriteLine("Usage: tht"); return;', 'Environment.Exit(9);')
+    Add-Type -TypeDefinition $programOne -OutputAssembly $artifactOne -OutputType ConsoleApplication
+    Add-Type -TypeDefinition $programTwo -OutputAssembly $artifactTwo -OutputType ConsoleApplication
+    Add-Type -TypeDefinition $brokenProgram -OutputAssembly $brokenArtifact -OutputType ConsoleApplication
     [System.IO.File]::WriteAllText($userPathStore, 'C:\Existing Bin')
 
     $env:THT_INSTALL_DIRECTORY = $installDirectory
-    $env:THT_BUILD_ARTIFACT = $artifact
+    $env:THT_BUILD_ARTIFACT = $artifactOne
-    $env:THT_BUILD_ARTIFACT_SHA256 = (Get-FileHash -Algorithm SHA256 -LiteralPath $artifact).Hash.ToLowerInvariant()
+    $env:THT_BUILD_ARTIFACT_SHA256 = (Get-FileHash -Algorithm SHA256 -LiteralPath $artifactOne).Hash.ToLowerInvariant()
     $env:THT_USER_PATH_FILE = $userPathStore
     & $installer
 
     $installed = Join-Path $installDirectory 'tht.exe'
     if (-not (Test-Path -LiteralPath $installed)) { throw 'installer did not create tht.exe' }
-    if ((& $installed version) -ne 'tht test version') { throw 'installed tht.exe did not return version' }
+    if ((& $installed version) -ne 'tht test version one') { throw 'installed tht.exe did not return version one' }
-    $firstBytes = [System.IO.File]::ReadAllBytes($installed)
+
+    $env:THT_BUILD_ARTIFACT = $brokenArtifact
+    $env:THT_BUILD_ARTIFACT_SHA256 = (Get-FileHash -Algorithm SHA256 -LiteralPath $brokenArtifact).Hash.ToLowerInvariant()
+    $brokenInstallFailed = $false
+    try {
+        & $installer
+    } catch {
+        $brokenInstallFailed = $true
+    }
+    if (-not $brokenInstallFailed) { throw 'installer accepted an invalid staged executable' }
+    if ((& $installed version) -ne 'tht test version one') { throw 'invalid staged executable replaced the existing command' }
+
+    $env:THT_BUILD_ARTIFACT = $artifactTwo
+    $env:THT_BUILD_ARTIFACT_SHA256 = (Get-FileHash -Algorithm SHA256 -LiteralPath $artifactTwo).Hash.ToLowerInvariant()
+    & $installer
+    if ((& $installed version) -ne 'tht test version two') { throw 'installer did not replace the existing command' }
 
     & $installer
-    if ((& $installed version) -ne 'tht test version') { throw 'installer was not idempotent' }
+    if ((& $installed version) -ne 'tht test version two') { throw 'installer was not idempotent' }
-    if (-not ([System.IO.File]::ReadAllBytes($installed).Length -eq $firstBytes.Length)) { throw 'replacement changed the unexpected binary' }
 
     $storedPath = [System.IO.File]::ReadAllText($userPathStore)
     $segments = $storedPath -split ';' | Where-Object { $_ -ne '' }

scripts/test-install-tht.sh

@@ -41,13 +41,15 @@ write_artifact "$artifact_one" "tht test version one"
 write_artifact "$artifact_two" "tht test version two"
 
 system_path=$PATH
+installer_bash=${THT_TEST_BASH:-/bin/bash}
+test -x "$installer_bash" || fail "THT_TEST_BASH must name an executable Bash interpreter"
 run_installer() {
   local artifact=$1
   THT_INSTALL_DIRECTORY="$test_directory" \
     THT_BUILD_ARTIFACT="$artifact" \
     THT_BUILD_ARTIFACT_SHA256="$(sha256 "$artifact")" \
     PATH="$test_directory:$system_path" \
-    bash "$installer"
+    "$installer_bash" "$installer"
 }
 
 run_installer "$artifact_one"