Preserve trailing commas in single-item SCSS lists (#19928)

Co-authored-by: fisker Cheung <lionkay@gmail.com>

changelog_unreleased/scss/19928.md

@@ -0,0 +1,13 @@
+#### Preserve trailing commas in single-item lists (#19928 by @kovsu)
+
+<!-- prettier-ignore -->
+```scss
+// Input
+$list: ("a",);
+
+// Prettier stable
+$list: ("a");
+
+// Prettier main
+$list: ("a",);
+```

src/language-css/print/parenthesized-value-group.js

@@ -15,9 +15,10 @@ import {
   lineSuffixBoundary,
   softline,
 } from "../../document/index.js";
+import getNextNonSpaceNonCommentCharacter from "../../utilities/get-next-non-space-non-comment-character.js";
 import isNextLineEmpty from "../../utilities/is-next-line-empty.js";
 import isNonEmptyArray from "../../utilities/is-non-empty-array.js";
-import { locEnd, locStart } from "../loc.js";
+import { locEnd } from "../loc.js";
 import {
   isConfigurationNode,
   isKeyInValuePairNode,
@@ -28,18 +29,34 @@ import {
 } from "../utilities/index.js";
 import { shouldPrintTrailingComma } from "./misc.js";
 
-function hasComma({ node, parent }, options) {
-  return Boolean(
-    node.source &&
-    options.originalText
-      .slice(locStart(node), locStart(parent.close))
-      .trimEnd()
-      .endsWith(","),
+function hasTrailingComma({ node, parent }, options) {
+  if (parent.type !== "value-paren_group") {
+    return false;
+  }
+
+  const nodes = node.type === "value-comma_group" ? node.groups : [node];
+  const lastValue = nodes.findLast((child) => child.type !== "value-comment");
+
+  if (!lastValue) {
+    return false;
+  }
+
+  const nextCharacter = getNextNonSpaceNonCommentCharacter(
+    options.originalText,
+    locEnd(lastValue),
   );
+  return nextCharacter === ",";
 }
 
 function printTrailingComma(path, options) {
-  if (isVarFunctionNode(path.grandparent) && hasComma(path, options)) {
+  if (
+    (isVarFunctionNode(path.grandparent) ||
+      (options.parser === "scss" &&
+        path.grandparent?.type !== "value-func" &&
+        path.parent.groups.length === 1 &&
+        !isKeyValuePairNode(path.parent.groups[0]))) &&
+    hasTrailingComma(path, options)
+  ) {
     return ",";
   }
 

tests/format/scss/trailing-comma/__snapshots__/format.test.js.snap

@@ -179,7 +179,7 @@ $z-indexes: (
 =====================================output=====================================
 .simplification {
   foo: (
-    calc() // It is a comment
+    calc(), // It is a comment
   );
 }
 
@@ -230,7 +230,7 @@ $z-indexes: (
 =====================================output=====================================
 .simplification {
   foo: (
-    calc() // It is a comment
+    calc(), // It is a comment
   );
 }
 
@@ -288,6 +288,110 @@ a {
 ================================================================================
 `;
 
+exports[`issue-6356.scss - {"trailingComma":"es5"} format 1`] = `
+====================================options=====================================
+parsers: ["scss"]
+trailingComma: "es5"
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+$single-string: ("a",);
+$single-space-list: (1 2 3,);
+$single-nested-list: ((1, 2),);
+@include assert-equal(daff-string-split(".a", "."), ("a",));
+
+$multiple-items: (1, 2,);
+$single-argument: foo(1,);
+
+$single-entry-map: (a: 1,);
+
+$comment-after-comma: ("a",
+  // ,
+);
+$comment-without-comma: ("a"
+  // ,
+);
+$empty-comment-after-comma: ("a",
+  //
+);
+
+=====================================output=====================================
+$single-string: ("a",);
+$single-space-list: (1 2 3,);
+$single-nested-list: ((1, 2),);
+@include assert-equal(daff-string-split(".a", "."), ("a",));
+
+$multiple-items: (1, 2);
+$single-argument: foo(1);
+
+$single-entry-map: (
+  a: 1,
+);
+
+$comment-after-comma: (
+  "a", // ,
+);
+$comment-without-comma: (
+  "a" // ,
+);
+$empty-comment-after-comma: (
+  "a", //
+);
+
+================================================================================
+`;
+
+exports[`issue-6356.scss - {"trailingComma":"none"} format 1`] = `
+====================================options=====================================
+parsers: ["scss"]
+trailingComma: "none"
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+$single-string: ("a",);
+$single-space-list: (1 2 3,);
+$single-nested-list: ((1, 2),);
+@include assert-equal(daff-string-split(".a", "."), ("a",));
+
+$multiple-items: (1, 2,);
+$single-argument: foo(1,);
+
+$single-entry-map: (a: 1,);
+
+$comment-after-comma: ("a",
+  // ,
+);
+$comment-without-comma: ("a"
+  // ,
+);
+$empty-comment-after-comma: ("a",
+  //
+);
+
+=====================================output=====================================
+$single-string: ("a",);
+$single-space-list: (1 2 3,);
+$single-nested-list: ((1, 2),);
+@include assert-equal(daff-string-split(".a", "."), ("a",));
+
+$multiple-items: (1, 2);
+$single-argument: foo(1);
+
+$single-entry-map: (
+  a: 1
+);
+
+$comment-after-comma: (
+  "a", // ,
+);
+$comment-without-comma: (
+  "a" // ,
+);
+$empty-comment-after-comma: (
+  "a", //
+);
+
+================================================================================
+`;
+
 exports[`issue-6920.scss - {"trailingComma":"es5"} format 1`] = `
 ====================================options=====================================
 parsers: ["scss"]
@@ -387,7 +491,7 @@ $breakpoint-map: (
 
 =====================================output=====================================
 $colors: hotpink deepskyblue firebrick;
-$list: (a);
+$list: (a,);
 $list: ("Helvetica", "Arial", sans-serif);
 $colors: ("red", "blue");
 $config: (
@@ -492,7 +596,7 @@ $breakpoint-map: (
 
 =====================================output=====================================
 $colors: hotpink deepskyblue firebrick;
-$list: (a);
+$list: (a,);
 $list: ("Helvetica", "Arial", sans-serif);
 $colors: ("red", "blue");
 $config: (

tests/format/scss/trailing-comma/issue-6356.scss

@@ -0,0 +1,19 @@
+$single-string: ("a",);
+$single-space-list: (1 2 3,);
+$single-nested-list: ((1, 2),);
+@include assert-equal(daff-string-split(".a", "."), ("a",));
+
+$multiple-items: (1, 2,);
+$single-argument: foo(1,);
+
+$single-entry-map: (a: 1,);
+
+$comment-after-comma: ("a",
+  // ,
+);
+$comment-without-comma: ("a"
+  // ,
+);
+$empty-comment-after-comma: ("a",
+  //
+);