Add support for 'files' configuration (#20272)

Co-authored-by: Daniel Jurek <djurek@microsoft.com>

eng/common/pipelines/templates/steps/check-spelling.yml

@@ -24,4 +24,5 @@ steps:
           -TargetBranch "origin/$("${{ parameters.TargetBranch }}" -replace "refs/heads/")"
           -SourceBranch ${{ parameters.SourceBranch }}
           -CspellConfigPath ${{ parameters.CspellConfigPath }}
+          -ExitWithError:(!$${{ parameters.ContinueOnError }})
         pwsh: true

eng/common/scripts/check-spelling-in-changed-files.ps1

@@ -7,7 +7,10 @@ Param (
     [string] $SourceBranch,
 
     [Parameter()]
-    [string] $CspellConfigPath = "./.vscode/cspell.json"
+    [string] $CspellConfigPath = "./.vscode/cspell.json",
+
+    [Parameter()]
+    [switch] $ExitWithError
 )
 
 $ErrorActionPreference = "Continue"
@@ -19,7 +22,7 @@ if ((Get-Command git | Measure-Object).Count -eq 0) {
 }
 
 if ((Get-Command npx | Measure-Object).Count -eq 0) { 
-    LogError "Could not locate npx. Install NodeJS (includes npm and npx) https://nodejs.org/en/download/"
+    LogError "Could not locate npx. Install NodeJS (includes npx and npx) https://nodejs.org/en/download/"
     exit 1
 }
 
@@ -43,16 +46,60 @@ if ($changedFilesCount -eq 0) {
     exit 0
 }
 
-$changedFilesString = $changedFiles -join ' '
+$changedFilePaths = @()
+foreach ($file in $changedFiles) {
+    $changedFilePaths += $file.Path
+}
 
-Write-Host "npx cspell --config $CspellConfigPath $changedFilesString"
-$spellingErrors = Invoke-Expression "npx cspell --config $CspellConfigPath $changedFilesString"
+# Using GetTempPath because it works on linux and windows. Setting .json
+# extension because cspell requires the file have a .json or .jsonc extension
+$cspellConfigTemporaryPath = Join-Path `
+    ([System.IO.Path]::GetTempPath()) `
+    "$([System.IO.Path]::GetRandomFileName()).json"
+
+$cspellConfigContent = Get-Content $CspellConfigPath -Raw
+$cspellConfig = ConvertFrom-Json $cspellConfigContent
+
+# If the config has no "files" property this adds it. If the config has a
+# "files" property this sets the value, overwriting the existing value. In this
+# case, spell checking is only intended to check files from $changedFiles so
+# preexisting entries in "files" will be overwritten.
+Add-Member `
+    -MemberType NoteProperty `
+    -InputObject $cspellConfig `
+    -Name "files" `
+    -Value $changedFilePaths `
+    -Force
+
+# Set the temporary config file with the mutated configuration. The temporary
+# location is used to configure the command and the original file remains
+# unchanged.
+Write-Host "Setting config in: $cspellConfigTemporaryPath"
+Set-Content `
+    -Path $cspellConfigTemporaryPath `
+    -Value (ConvertTo-Json $cspellConfig -Depth 100)
+
+# Use the mutated configuration file when calling cspell
+Write-Host "npx cspell lint --config $cspellConfigTemporaryPath"
+$spellingErrors = npx cspell lint --config $cspellConfigTemporaryPath
 
 if ($spellingErrors) {
+    $errorLoggingFunction = Get-Item 'Function:LogWarning'
+    if ($ExitWithError) {
+        $errorLoggingFunction = Get-Item 'Function:LogError'
+    }
+
     foreach ($spellingError in $spellingErrors) { 
-        LogWarning $spellingError
+        &$errorLoggingFunction $spellingError
+    }
+    &$errorLoggingFunction "Spelling errors detected. To correct false positives or learn about spell checking see: https://aka.ms/azsdk/engsys/spellcheck"
+
+    if ($ExitWithError) {
+        exit 1
     }
-    LogWarning "Spelling errors detected. To correct false positives or learn about spell checking see: https://aka.ms/azsdk/engsys/spellcheck"
+} else {
+    Write-Host "No spelling errors detected. Removing temporary config file."
+    Remove-Item -Path $cspellConfigTemporaryPath -Force
 }
 
 exit 0
@@ -66,22 +113,26 @@ This script checks files that have changed relative to a base branch (default
 branch) for spelling errors. Dictionaries and spelling configurations reside 
 in a configurable `cspell.json` location.
 
-This script uses `npx` and assumes that NodeJS (and by extension `npm` and `npx`
-) are installed on the machine. If it does not detect `npx` it will warn the 
-user and exit with an error. 
+This script uses `npx` and assumes that NodeJS (and by extension `npm` and
+`npx`) are installed on the machine. If it does not detect `npx` it will warn
+the user and exit with an error.
 
 The entire file is scanned, not just changed sections. Spelling errors in parts 
 of the file not touched will still be shown.
 
-Running this on the local machine will trigger tests 
+This script copies the config file supplied in CspellConfigPath to a temporary
+location, mutates the config file to include only the files that have changed,
+and then uses the mutated config file to call cspell. In the case of success
+the temporary file is deleted. In the case of failure the temporary file, whose
+location was logged to the console, remains on disk.
 
 .PARAMETER TargetBranch
 Git ref to compare changes. This is usually the "base" (GitHub) or "target" 
 (DevOps) branch for which a pull request would be opened.
 
-.PARAMETER SouceBranch
+.PARAMETER SourceBranch
 Git ref to use instead of changes in current repo state. Use `HEAD` here to 
-check spelling of files that have been committed and exlcude any new files or
+check spelling of files that have been committed and exclude any new files or
 modified files that are not committed. This is most useful in CI scenarios where
 builds may have modified the state of the repo. Leaving this parameter blank  
 includes files for whom changes have not been committed. 
@@ -90,6 +141,9 @@ includes files for whom changes have not been committed.
 Optional location to use for cspell.json path. Default value is 
 `./.vscode/cspell.json`
 
+.PARAMETER ExitWithError
+Exit with error code 1 if spelling errors are detected.
+
 .EXAMPLE
 ./eng/common/scripts/check-spelling-in-changed-files.ps1 -TargetBranch 'target_branch_name'