A single leading space (such as in the copyright header) should not override an otherwise 100% tab-indented file. (fixes #506)

Author: nedtwigg

jvm/CHANGELOG.md

@@ -11,6 +11,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Fixed
+- A single leading space (such as in the copyright header) should not override an otherwise 100% tab-indented file. ([#506](https://github.com/diffplug/selfie/issues/506))
 
 ## [2.4.1] - 2024-10-07
 ### Fixed

jvm/selfie-lib/src/commonMain/kotlin/com/diffplug/selfie/guts/EscapeLeadingWhitespace.kt

@@ -35,7 +35,7 @@ internal enum class EscapeLeadingWhitespace {
               .lineSequence()
               .mapNotNull { line ->
                 val whitespace = line.takeWhile { it.isWhitespace() }
-                if (whitespace.isEmpty()) null
+                if (whitespace.isEmpty() || whitespace == " ") null
                 else if (whitespace.all { it == ' ' }) ' '
                 else if (whitespace.all { it == '\t' }) '\t' else MIXED
               }

jvm/selfie-lib/src/commonTest/kotlin/com/diffplug/selfie/guts/EscapeLeadingWhitespaceTest.kt

@@ -29,16 +29,28 @@ class EscapeLeadingWhitespaceTest {
     appropriateFor("abc\nabc") shouldBe ALWAYS
 
     // all spaces -> only tabs need escape
-    appropriateFor(" ") shouldBe ONLY_ON_TAB
+    appropriateFor(" ") shouldBe ALWAYS
     appropriateFor("  ") shouldBe ONLY_ON_TAB
-    appropriateFor(" \n ") shouldBe ONLY_ON_TAB
+    appropriateFor("  \n  ") shouldBe ONLY_ON_TAB
 
     // all tabs -> only space needs escape
     appropriateFor("\t") shouldBe ONLY_ON_SPACE
     appropriateFor("\t\t") shouldBe ONLY_ON_SPACE
     appropriateFor("\t\n\t") shouldBe ONLY_ON_SPACE
 
     // it's a mess -> everything needs escape
-    appropriateFor("\t\n ") shouldBe ALWAYS
+    appropriateFor("\t\n  ") shouldBe ALWAYS
+
+    // single spaces and tabs -> only tabs need escape
+    appropriateFor(
+        """
+/*
+${' '}* Copyright
+${' '}*/
+interface Foo {
+${'\t'}fun bar()
+}
+""") shouldBe
+        ONLY_ON_SPACE
   }
 }