Support disabling import optimization from command line

Summary:
Turns out we did not connecting this to our CLI interface, making it impossible to skip imports.

Slightly awkward naming (i.e. the flag negates), but it gets the job done, and we don't have a real parser for flags no is the dependency on one worth it.

Reviewed By: hick209

Differential Revision: D42105735

fbshipit-source-id: 8ddab2af5310fd59d86e29d6c827b33d47ab10b1

core/src/main/java/com/facebook/ktfmt/cli/Main.kt

@@ -70,7 +70,7 @@ class Main(
   fun run(): Int {
     if (parsedArgs.fileNames.isEmpty()) {
       err.println(
-          "Usage: ktfmt [--dropbox-style | --google-style | --kotlinlang-style] [--dry-run] [--set-exit-if-changed] [--stdin-name=<name>] File1.kt File2.kt ...")
+          "Usage: ktfmt [--dropbox-style | --google-style | --kotlinlang-style] [--dry-run] [--set-exit-if-changed] [--stdin-name=<name>] [--do-not-remove-unused-imports] File1.kt File2.kt ...")
       err.println("Or: ktfmt @file")
       return 1
     }

core/src/main/java/com/facebook/ktfmt/cli/ParsedArgs.kt

@@ -52,6 +52,7 @@ data class ParsedArgs(
       var formattingOptions = FormattingOptions()
       var dryRun = false
       var setExitIfChanged = false
+      var removeUnusedImports = true
       var stdinName: String? = null
 
       for (arg in args) {
@@ -61,14 +62,21 @@ data class ParsedArgs(
           arg == "--kotlinlang-style" -> formattingOptions = Formatter.KOTLINLANG_FORMAT
           arg == "--dry-run" || arg == "-n" -> dryRun = true
           arg == "--set-exit-if-changed" -> setExitIfChanged = true
+          arg == "--do-not-remove-unused-imports" -> removeUnusedImports = false
           arg.startsWith("--stdin-name") -> stdinName = parseKeyValueArg(err, "--stdin-name", arg)
           arg.startsWith("--") -> err.println("Unexpected option: $arg")
           arg.startsWith("@") -> err.println("Unexpected option: $arg")
           else -> fileNames.add(arg)
         }
       }
 
-      return ParsedArgs(fileNames, formattingOptions, dryRun, setExitIfChanged, stdinName)
+      return ParsedArgs(
+          fileNames,
+          formattingOptions.copy(removeUnusedImports = removeUnusedImports),
+          dryRun,
+          setExitIfChanged,
+          stdinName,
+      )
     }
 
     private fun parseKeyValueArg(err: PrintStream, key: String, arg: String): String? {

core/src/test/java/com/facebook/ktfmt/cli/ParsedArgsTest.kt

@@ -107,6 +107,33 @@ class ParsedArgsTest {
     assertThat(parsed.setExitIfChanged).isTrue()
   }
 
+  @Test
+  fun `parseOptions defaults to removing imports`() {
+    val (parsed, _) = parseTestOptions("foo.kt")
+    assertThat(parsed.formattingOptions.removeUnusedImports).isTrue()
+  }
+
+  @Test
+  fun `parseOptions recognizes --do-not-remove-unused-imports to removing imports`() {
+    val (parsed, _) = parseTestOptions("--do-not-remove-unused-imports", "foo.kt")
+    assertThat(parsed.formattingOptions.removeUnusedImports).isFalse()
+  }
+
+  @Test
+  fun `parseOptions handles dropbox style and --do-not-remove-unused-imports`() {
+    val (parsed, _) =
+        parseTestOptions("--do-not-remove-unused-imports", "--dropbox-style", "foo.kt")
+    assertThat(parsed.formattingOptions.removeUnusedImports).isFalse()
+    assertThat(parsed.formattingOptions.style).isEqualTo(FormattingOptions.Style.DROPBOX)
+  }
+
+  @Test
+  fun `parseOptions handles google style and --do-not-remove-unused-imports`() {
+    val (parsed, _) = parseTestOptions("--do-not-remove-unused-imports", "--google-style", "foo.kt")
+    assertThat(parsed.formattingOptions.removeUnusedImports).isFalse()
+    assertThat(parsed.formattingOptions.style).isEqualTo(FormattingOptions.Style.GOOGLE)
+  }
+
   @Test
   fun `parseOptions --stdin-name`() {
     val (parsed, _) = parseTestOptions("--stdin-name=my/foo.kt")