Keep file content when the file is virtual (#6519)

Virtual files are not stored on disk and can thus also not be read
from there again. Their content needs to stay in memory and be modified
right there.

CHANGELOG.md

@@ -12,6 +12,10 @@
 
 ### Enhancements
 
+* Print fixed code read from stdin to stdout.  
+  [SimplyDanny](https://github.com/SimplyDanny)
+  [#6501](https://github.com/realm/SwiftLint/issues/6501)
+
 * Add `ignored_literal_argument_functions` option to the `force_unwrapping` rule
   to skip violations for configurable function calls when all arguments are
   literal values (e.g. `URL(string: "https://example.com")!`). Defaults

Source/SwiftLintCore/Extensions/SwiftLintFile+Cache.swift

@@ -182,7 +182,9 @@ extension SwiftLintFile {
 
     /// Invalidates all cached data for this file.
     public func invalidateCache() {
-        file.clearCaches()
+        if !isVirtual {
+            file.clearCaches()
+        }
         responseCache.invalidate(self)
         assertHandlerCache.invalidate(self)
         structureDictionaryCache.invalidate(self)

Source/SwiftLintCore/Extensions/SwiftLintFile+Regex.swift

@@ -134,6 +134,7 @@ extension SwiftLintFile {
         guard string.isNotEmpty else {
             return
         }
+        defer { invalidateCache() }
         file.contents += string
         if isVirtual {
             return
@@ -147,13 +148,13 @@ extension SwiftLintFile {
         _ = fileHandle.seekToEndOfFile()
         fileHandle.write(stringData)
         fileHandle.closeFile()
-        invalidateCache()
     }
 
     public func write<S: StringProtocol>(_ string: S) {
         guard string != contents else {
             return
         }
+        defer { invalidateCache() }
         file.contents = String(string)
         if isVirtual {
             return
@@ -169,7 +170,6 @@ extension SwiftLintFile {
         } catch {
             queuedFatalError("can't write file to \(path)")
         }
-        invalidateCache()
     }
 
     public func ruleEnabled(violatingRanges: [NSRange], for rule: some Rule) -> [NSRange] {