Keep empty import attributes and assertions (prettier#15757)

changelog_unreleased/javascript/15757.md

@@ -0,0 +1,16 @@
+#### Keep empty import attributes and assertions (#15757 by @fisker)
+
+<!-- prettier-ignore -->
+```js
+// Input
+import foo from "foo" with {};
+import bar from "bar" assert {};
+
+// Prettier stable
+import foo from "foo";
+import bar from "bar";
+
+// Prettier main
+import foo from "foo" with {};
+import bar from "bar" assert {};
+```

src/language-js/print/module.js

@@ -249,6 +249,24 @@ function shouldPrintSpecifiers(node, options) {
   return text.trimEnd().endsWith("from");
 }
 
+function shouldPrintAttributes(node, options) {
+  if (!node.source) {
+    return false;
+  }
+
+  if (isNonEmptyArray(node.attributes) || isNonEmptyArray(node.assertions)) {
+    return true;
+  }
+
+  const text = getTextWithoutComments(
+    options,
+    locEnd(node.source),
+    locEnd(node),
+  ).trimStart();
+
+  return text.startsWith("with") || text.startsWith("assert");
+}
+
 function getTextWithoutComments(options, start, end) {
   let text = options.originalText.slice(start, end);
 
@@ -282,15 +300,20 @@ function getImportAttributesOrAssertionsKeyword(node, options) {
   if (
     // Babel parser add this property to indicate the keyword is `assert`
     node.extra?.deprecatedAssertSyntax ||
-    !isNonEmptyArray(node.attributes)
+    (isNonEmptyArray(node.assertions) && !isNonEmptyArray(node.attributes))
   ) {
     return "assert";
   }
 
+  if (!isNonEmptyArray(node.assertions) && isNonEmptyArray(node.attributes)) {
+    return "with";
+  }
+
+  const firstAttribute = node.attributes?.[0] ?? node.assertions?.[0];
   const textBetweenSourceAndAttributes = getTextWithoutComments(
     options,
     locEnd(node.source),
-    locStart(node.attributes[0]),
+    firstAttribute ? locStart(firstAttribute) : locEnd(node),
   );
 
   if (textBetweenSourceAndAttributes.trimStart().startsWith("assert")) {
@@ -307,24 +330,33 @@ function getImportAttributesOrAssertionsKeyword(node, options) {
 function printImportAttributes(path, options, print) {
   const { node } = path;
 
+  if (!shouldPrintAttributes(node, options)) {
+    return "";
+  }
+
+  const keyword = getImportAttributesOrAssertionsKeyword(node, options);
+  /** @type{Doc[]} */
+  const parts = [` ${keyword} {`];
+
   const property = isNonEmptyArray(node.attributes)
     ? "attributes"
     : isNonEmptyArray(node.assertions)
       ? "assertions"
       : undefined;
+  if (property) {
+    if (options.bracketSpacing) {
+      parts.push(" ");
+    }
 
-  if (!property) {
-    return "";
+    parts.push(join(", ", path.map(print, property)));
+
+    if (options.bracketSpacing) {
+      parts.push(" ");
+    }
   }
+  parts.push("}");
 
-  const keyword = getImportAttributesOrAssertionsKeyword(node, options);
-  return [
-    ` ${keyword} {`,
-    options.bracketSpacing ? " " : "",
-    join(", ", path.map(print, property)),
-    options.bracketSpacing ? " " : "",
-    "}",
-  ];
+  return parts;
 }
 
 function printModuleSpecifier(path, options, print) {

tests/format/js/import-assertions/__snapshots__/jsfmt.spec.js.snap

@@ -86,12 +86,12 @@ import * as bar from "bar.json" assert { }
 import * as baz from "baz.json" assert { /* comment */ }
 =====================================output=====================================
 export * as foo from "foo.json";
-export * as bar from "bar.json";
-export * as baz from "baz.json" /* comment */;
+export * as bar from "bar.json" assert {};
+export * as baz from "baz.json" /* comment */ assert {};
 
 import * as foo from "foo.json";
-import * as bar from "bar.json";
-import * as baz from "baz.json" /* comment */;
+import * as bar from "bar.json" assert {};
+import * as baz from "baz.json" /* comment */ assert {};
 
 ================================================================================
 `;

tests/format/js/import-assertions/bracket-spacing/__snapshots__/jsfmt.spec.js.snap

@@ -69,7 +69,7 @@ printWidth: 80
 =====================================input======================================
 export * as bar from "bar.json" assert { }
 =====================================output=====================================
-export * as bar from "bar.json";
+export * as bar from "bar.json" assert {};
 
 ================================================================================
 `;

tests/format/js/import-attributes/__snapshots__/jsfmt.spec.js.snap

@@ -87,12 +87,12 @@ import * as baz from "baz.json" with { /* comment */ }
 
 =====================================output=====================================
 export * as foo from "foo.json";
-export * as bar from "bar.json";
-export * as baz from "baz.json" /* comment */;
+export * as bar from "bar.json" with {};
+export * as baz from "baz.json" /* comment */ with {};
 
 import * as foo from "foo.json";
-import * as bar from "bar.json";
-import * as baz from "baz.json" /* comment */;
+import * as bar from "bar.json" with {};
+import * as baz from "baz.json" /* comment */ with {};
 
 ================================================================================
 `;

tests/format/js/import-attributes/bracket-spacing/__snapshots__/jsfmt.spec.js.snap

@@ -69,7 +69,7 @@ printWidth: 80
 =====================================input======================================
 export * as bar from "bar.json" with { }
 =====================================output=====================================
-export * as bar from "bar.json";
+export * as bar from "bar.json" with {};
 
 ================================================================================
 `;