Do not merge opening quotes of multiline string template with (single line) function signature (#2609)

Closes #2592

2 files changed, 74 insertions, 8 deletions

diff --git a/ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionSignatureRule.kt b/ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionSignatureRule.kt
index d41b35e5..b8f09641 100644
--- a/ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionSignatureRule.kt
+++ b/ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionSignatureRule.kt
@@ -1,5 +1,6 @@
 package com.pinterest.ktlint.ruleset.standard.rules
 
+import com.pinterest.ktlint.rule.engine.core.api.ElementType
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.ANNOTATED_EXPRESSION
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.ANNOTATION
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.ANNOTATION_ENTRY
@@ -33,6 +34,7 @@ import com.pinterest.ktlint.rule.engine.core.api.editorconfig.INDENT_STYLE_PROPE
 import com.pinterest.ktlint.rule.engine.core.api.editorconfig.MAX_LINE_LENGTH_PROPERTY
 import com.pinterest.ktlint.rule.engine.core.api.editorconfig.MAX_LINE_LENGTH_PROPERTY_OFF
 import com.pinterest.ktlint.rule.engine.core.api.indent
+import com.pinterest.ktlint.rule.engine.core.api.isCodeLeaf
 import com.pinterest.ktlint.rule.engine.core.api.isWhiteSpace
 import com.pinterest.ktlint.rule.engine.core.api.isWhiteSpaceWithNewline
 import com.pinterest.ktlint.rule.engine.core.api.nextCodeLeaf
@@ -563,14 +565,16 @@ public class FunctionSignatureRule :
                             return
                         }
                     val mergeWithFunctionSignature =
-                        if (firstLineOfBodyExpression.length < maxLengthRemainingForFirstLineOfBodyExpression) {
-                            functionBodyExpressionWrapping == default ||
-                                (functionBodyExpressionWrapping == multiline && functionBodyExpressionLines.size == 1) ||
-                                node.isMultilineFunctionSignatureWithoutExplicitReturnType(
-                                    lastNodeOfFunctionSignatureWithBodyExpression,
-                                )
-                        } else {
-                            false
+                        when {
+                            firstLineOfBodyExpression.length < maxLengthRemainingForFirstLineOfBodyExpression -> {
+                                (functionBodyExpressionWrapping == default && !functionBodyExpressionNodes.isMultilineStringTemplate()) ||
+                                    (functionBodyExpressionWrapping == multiline && functionBodyExpressionLines.size == 1) ||
+                                    node.isMultilineFunctionSignatureWithoutExplicitReturnType(
+                                        lastNodeOfFunctionSignatureWithBodyExpression,
+                                    )
+                            }
+
+                            else -> false
                         }
                     if (mergeWithFunctionSignature) {
                         emit(
@@ -621,6 +625,17 @@ public class FunctionSignatureRule :
             }
     }
 
+    private fun List<ASTNode>.isMultilineStringTemplate() =
+        first { it.isCodeLeaf() }
+            .let {
+                it.elementType == ElementType.OPEN_QUOTE &&
+                    it
+                        .nextLeaf()
+                        ?.text
+                        .orEmpty()
+                        .startsWith("\n")
+            }
+
     private fun ASTNode.isMultilineFunctionSignatureWithoutExplicitReturnType(lastNodeOfFunctionSignatureWithBodyExpression: ASTNode?) =
         functionSignatureNodes()
             .childrenBetween(
diff --git a/ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionSignatureRuleTest.kt b/ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionSignatureRuleTest.kt
index 9473d606..0fbf6717 100644
--- a/ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionSignatureRuleTest.kt
+++ b/ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionSignatureRuleTest.kt
@@ -13,6 +13,7 @@ import com.pinterest.ktlint.test.KtLintAssertThat.Companion.EOL_CHAR
 import com.pinterest.ktlint.test.KtLintAssertThat.Companion.MAX_LINE_LENGTH_MARKER
 import com.pinterest.ktlint.test.KtLintAssertThat.Companion.assertThatRuleBuilder
 import com.pinterest.ktlint.test.LintViolation
+import com.pinterest.ktlint.test.MULTILINE_STRING_QUOTE
 import org.assertj.core.api.Assertions.assertThat
 import org.assertj.core.api.Assertions.assertThatExceptionOfType
 import org.junit.jupiter.api.DisplayName
@@ -1313,6 +1314,56 @@ class FunctionSignatureRuleTest {
             .hasNoLintViolations()
     }
 
+    @Test
+    fun `Issue 2592 - Given a function signature with an expression body that is multiline raw string literal then do not join the first leaf with the function signature`() {
+        val code =
+            """
+            // $MAX_LINE_LENGTH_MARKER        $EOL_CHAR
+            fun foo1(): String =
+                $MULTILINE_STRING_QUOTE
+                some text
+                $MULTILINE_STRING_QUOTE.trimIndent()
+            fun foo2() =
+                $MULTILINE_STRING_QUOTE
+                some text
+                $MULTILINE_STRING_QUOTE.trimIndent()
+            """.trimIndent()
+        functionSignatureWrappingRuleAssertThat(code)
+            .setMaxLineLength()
+            .withEditorConfigOverride(FUNCTION_BODY_EXPRESSION_WRAPPING_PROPERTY to default)
+            .hasNoLintViolations()
+    }
+
+    @Test
+    fun `Issue 2592 - Given a multiline function signature with an expression body that is multiline raw string literal then do join the first leaf with the function signature`() {
+        val code =
+            """
+            // $MAX_LINE_LENGTH_MARKER        $EOL_CHAR
+            fun foo(
+                foo: Foo,
+                bar: Bar,
+            ) =
+                $MULTILINE_STRING_QUOTE
+                some text
+                $MULTILINE_STRING_QUOTE.trimIndent()
+            """.trimIndent()
+        val formattedCode =
+            """
+            // $MAX_LINE_LENGTH_MARKER        $EOL_CHAR
+            fun foo(
+                foo: Foo,
+                bar: Bar,
+            ) = $MULTILINE_STRING_QUOTE
+                some text
+                $MULTILINE_STRING_QUOTE.trimIndent()
+            """.trimIndent()
+        functionSignatureWrappingRuleAssertThat(code)
+            .setMaxLineLength()
+            .withEditorConfigOverride(FUNCTION_BODY_EXPRESSION_WRAPPING_PROPERTY to default)
+            .hasLintViolation(5, 4, "First line of body expression fits on same line as function signature")
+            .isFormattedAs(formattedCode)
+    }
+
     private companion object {
         const val UNEXPECTED_SPACES = "  "
         const val NO_SPACE = ""