fix: Package json hash difference between linux and windows (#24321)

Windows and Linux generated a different
hash for the package json content
as jackson default indenter
used system line separator.

Fixes #24305

Author: caalador

flow-build-tools/src/test/java/com/vaadin/flow/server/frontend/TaskUpdatePackagesNpmTest.java

@@ -31,6 +31,7 @@
 
 import net.jcip.annotations.NotThreadSafe;
 import org.apache.commons.io.FileUtils;
+import org.junit.Assert;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
@@ -1589,6 +1590,72 @@ void pnpmIsInUse_pwaOfflineDisabledAfterEnabled_flattenedOverridesRemoved()
         }
     }
 
+    /**
+     * This tests that other systems generate the same hash as we get for a
+     * Windows machine. There was an issue in the jackson indenter that used
+     * different line separators on windows (\r\n) and linux (\n).
+     */
+    @Test
+    void windowsHashedPackageJson_otherSystemsGetSameHash() {
+        var json = """
+                {
+                  "name": "no-name",
+                  "license": "UNLICENSED",
+                  "type": "module",
+                  "dependencies": {
+                    "@vaadin/common-frontend": "0.0.22",
+                    "@vaadin/react-components": "25.1.2",
+                    "@vaadin/vaadin-development-mode-detector": "2.0.7",
+                    "adaptivecards": "1.2.6",
+                    "brace": "0.11.1",
+                    "date-fns": "4.1.0",
+                    "lit": "3.3.2",
+                    "react": "19.2.4",
+                    "react-dom": "19.2.4",
+                    "react-router": "7.13.1"
+                  },
+                  "devDependencies": {
+                    "@babel/plugin-proposal-object-rest-spread": "7.20.7",
+                    "@types/node": "25.5.0",
+                    "@types/react": "19.2.14",
+                    "@types/react-dom": "19.2.3",
+                    "typescript": "5.9.3",
+                    "vite": "7.3.2",
+                    "vite-plugin-checker": "0.12.0"
+                  },
+                  "vaadin": {
+                    "dependencies": {
+                        "@vaadin/common-frontend": "0.0.22",
+                        "@vaadin/react-components": "25.1.2",
+                        "@vaadin/vaadin-development-mode-detector": "2.0.7",
+                        "adaptivecards": "1.2.6",
+                        "brace": "0.11.1",
+                        "date-fns": "4.1.0",
+                        "lit": "3.3.2",
+                        "react": "19.2.4",
+                        "react-dom": "19.2.4",
+                        "react-router": "7.13.1"
+                    },
+                    "devDependencies": {
+                        "@babel/plugin-proposal-object-rest-spread": "7.20.7",
+                        "@types/node": "25.5.0",
+                        "@types/react": "19.2.14",
+                        "@types/react-dom": "19.2.3",
+                        "typescript": "5.9.3",
+                        "vite": "7.3.2",
+                        "vite-plugin-checker": "0.12.0"
+                    },
+                    "hash": "a4b492aecb32fe13902befbcc4ad0efbe6417273e8ca60346c4839973ae8242c"
+                  }
+                }
+                """;
+
+        var packageJson = JacksonUtils.readTree(json);
+        var hash = TaskUpdatePackages.generatePackageJsonHash(packageJson);
+        Assert.assertEquals(packageJson.get("vaadin").get("hash").asString(),
+                hash);
+    }
+
     @Test
     void generatePackageJsonHash_pnpmOverrides_includedInHash()
             throws IOException {

flow-server/src/main/java/com/vaadin/flow/internal/JacksonUtils.java

@@ -36,6 +36,7 @@
 import tools.jackson.core.JsonGenerator;
 import tools.jackson.core.json.JsonReadFeature;
 import tools.jackson.core.type.TypeReference;
+import tools.jackson.core.util.DefaultIndenter;
 import tools.jackson.core.util.DefaultPrettyPrinter;
 import tools.jackson.core.util.Separators;
 import tools.jackson.core.util.Separators.Spacing;
@@ -574,6 +575,10 @@ public static String toFileJson(JsonNode node) throws JacksonException {
         DefaultPrettyPrinter filePrinter = new DefaultPrettyPrinter(
                 Separators.createDefaultInstance()
                         .withObjectNameValueSpacing(Spacing.AFTER));
+        // Force LF line endings so output (and any hash derived from it) is
+        // identical across platforms; Jackson's default object indenter uses
+        // the system line separator (\r\n on Windows, \n elsewhere).
+        filePrinter.indentObjectsWith(new DefaultIndenter("  ", "\n"));
         return objectMapper.writer().with(filePrinter).writeValueAsString(node);
     }
 

flow-server/src/test/java/com/vaadin/flow/internal/JacksonUtilsTest.java

@@ -497,7 +497,7 @@ public void toFileJson() throws JacksonException {
                     "childValue": "child"
                   },
                   "parentValue": "parent"
-                }""", JacksonUtils.toFileJson(json).replace("\r\n", "\n"));
+                }""", JacksonUtils.toFileJson(json));
 
     }