new Rule: No line break before assignment

ktlint-ruleset-standard/src/main/kotlin/com/github/shyiko/ktlint/ruleset/standard/NoLineBreakBeforeAssignmentRule.kt

@@ -0,0 +1,23 @@
+package com.github.shyiko.ktlint.ruleset.standard
+
+import com.github.shyiko.ktlint.core.Rule
+import org.jetbrains.kotlin.com.intellij.lang.ASTNode
+import org.jetbrains.kotlin.com.intellij.psi.PsiWhiteSpace
+import org.jetbrains.kotlin.com.intellij.psi.impl.source.tree.LeafPsiElement
+import org.jetbrains.kotlin.lexer.KtTokens
+
+class NoLineBreakBeforeAssignmentRule : Rule("no-line-break-before-assignment") {
+
+ override fun visit(node: ASTNode, autoCorrect: Boolean, emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit) {
+ if (node.elementType == KtTokens.EQ) {
+ val prevElement = node.treePrev?.psi
+ if (prevElement is PsiWhiteSpace && prevElement.text.contains("\n")) {
+ emit(node.startOffset, "Line break before assignment is not allowed", true)
+ if (autoCorrect) {
+ (node.treeNext?.psi as LeafPsiElement).replaceWithText(prevElement.text)
+ (prevElement as LeafPsiElement).replaceWithText(" ")
+ }
+ }
+ }
+ }
+}

ktlint-ruleset-standard/src/main/kotlin/com/github/shyiko/ktlint/ruleset/standard/StandardRuleSetProvider.kt

@@ -28,6 +28,7 @@ class StandardRuleSetProvider : RuleSetProvider {
  SpacingAroundCurlyRule(),
  SpacingAroundKeywordRule(),
  SpacingAroundOperatorsRule(),
- StringTemplateRule()
+ StringTemplateRule(),
+ NoLineBreakBeforeAssignmentRule()
  )
 }

ktlint-ruleset-standard/src/test/kotlin/com/github/shyiko/ktlint/ruleset/standard/NoLineBreakBeforeAssignmentRuleTest.kt

@@ -0,0 +1,69 @@
+package com.github.shyiko.ktlint.ruleset.standard
+
+import com.github.shyiko.ktlint.core.LintError
+import com.github.shyiko.ktlint.test.format
+import com.github.shyiko.ktlint.test.lint
+import org.assertj.core.api.Assertions.assertThat
+import org.testng.annotations.Test
+
+const val ruleId = "no-line-break-before-assignment"
+
+class NoLineBreakBeforeAssignmentRuleTest {
+ @Test
+ fun testAllPartsOnSameLineIsValid() {
+ assertThat(NoLineBreakBeforeAssignmentRule().lint(
+ """
+ val valA = ""
+ """.trimIndent()
+ )).isEmpty()
+ }
+
+ @Test
+ fun testLineBreakAfterAssignmentIsValid() {
+ assertThat(NoLineBreakBeforeAssignmentRule().lint(
+ """
+ val valA =
+ ""
+ """.trimIndent()
+ )).isEmpty()
+ }
+
+ @Test
+ fun testLineBreakBeforeAssignmentIsViolation() {
+ assertThat(NoLineBreakBeforeAssignmentRule().lint(
+ """
+ val valA
+ = ""
+ """.trimIndent()
+ )).isEqualTo(listOf(
+ LintError(2, 7, ruleId, "Line break before assignment is not allowed")
+ ))
+ }
+
+ @Test
+ fun testViolationInFunction() {
+ assertThat(NoLineBreakBeforeAssignmentRule().lint(
+ """
+ fun funA()
+ = ""
+ """.trimIndent()
+ )).isEqualTo(listOf(
+ LintError(2, 7, ruleId, "Line break before assignment is not allowed")
+ ))
+ }
+
+ @Test
+ fun testFixViolationByRemovingLineBreakFromLeftAndPutItOnRightSide() {
+ assertThat(NoLineBreakBeforeAssignmentRule().format(
+ """
+ fun funA()
+ = ""
+ """.trimIndent()
+ )).isEqualTo(
+ """
+ fun funA() =
+ ""
+ """.trimIndent()
+ )
+ }
+}