fix(maven): bumpVersion update SNAPSHOT versions

lib/modules/manager/maven/__fixtures__/minimum_snapshot.pom.xml

@@ -0,0 +1,6 @@
+<project>
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>com.mycompany.app</groupId>
+  <artifactId>my-app</artifactId>
+  <version>0.0.1-SNAPSHOT</version>
+</project>

lib/modules/manager/maven/extract.spec.ts

@@ -243,6 +243,20 @@ describe('modules/manager/maven/extract', () => {
         packageFileVersion: '1',
       });
     });
+
+    it('tries minimum snapshot manifests', () => {
+      const res = extractPackage(
+        Fixtures.get(`minimum_snapshot.pom.xml`),
+        'some-file',
+      );
+      expect(res).toEqual({
+        datasource: 'maven',
+        deps: [],
+        mavenProps: {},
+        packageFile: 'some-file',
+        packageFileVersion: '0.0.1-SNAPSHOT',
+      });
+    });
   });
 
   describe('resolveParents', () => {

lib/modules/manager/maven/update.spec.ts

@@ -5,6 +5,7 @@ import { bumpPackageVersion, updateDependency } from './update';
 
 const simpleContent = Fixtures.get(`simple.pom.xml`);
 const minimumContent = Fixtures.get(`minimum.pom.xml`);
+const minimumSnapshotContent = Fixtures.get(`minimum_snapshot.pom.xml`);
 const prereleaseContent = Fixtures.get(`prerelease.pom.xml`);
 
 describe('modules/manager/maven/update', () => {
@@ -30,6 +31,53 @@ describe('modules/manager/maven/update', () => {
       expect(project.valueWithPath('version')).toBe('0.0.2');
     });
 
+    it('bumps pom.xml version keeping SNAPSHOT', () => {
+      const { bumpedContent } = bumpPackageVersion(
+        minimumSnapshotContent,
+        '0.0.1-SNAPSHOT',
+        'patch',
+      );
+
+      const project = new XmlDocument(bumpedContent!);
+      expect(project.valueWithPath('version')).toBe('0.0.2-SNAPSHOT');
+    });
+
+    it('bumps pom.xml minor version keeping SNAPSHOT', () => {
+      const { bumpedContent } = bumpPackageVersion(
+        minimumSnapshotContent,
+        '0.0.1-SNAPSHOT',
+        'minor',
+      );
+
+      const project = new XmlDocument(bumpedContent!);
+      expect(project.valueWithPath('version')).toBe('0.1.0-SNAPSHOT');
+    });
+
+    it('bumps pom.xml major version keeping SNAPSHOT', () => {
+      const { bumpedContent } = bumpPackageVersion(
+        minimumSnapshotContent,
+        '0.0.1-SNAPSHOT',
+        'major',
+      );
+
+      const project = new XmlDocument(bumpedContent!);
+      expect(project.valueWithPath('version')).toBe('1.0.0-SNAPSHOT');
+    });
+
+    it('bumps pom.xml version keeping qualifier with -SNAPSHOT', () => {
+      const { bumpedContent } = bumpPackageVersion(
+        minimumSnapshotContent.replace(
+          '0.0.1-SNAPSHOT',
+          '0.0.1-qualified-SNAPSHOT',
+        ),
+        '0.0.1-qualified-SNAPSHOT',
+        'patch',
+      );
+
+      const project = new XmlDocument(bumpedContent!);
+      expect(project.valueWithPath('version')).toBe('0.0.2-qualified-SNAPSHOT');
+    });
+
     it('does not bump version twice', () => {
       const { bumpedContent } = bumpPackageVersion(
         simpleContent,
@@ -71,6 +119,17 @@ describe('modules/manager/maven/update', () => {
       expect(bumpedContent).toEqual(simpleContent);
     });
 
+    it('bumps pom.xml version to SNAPSHOT with prerelease', () => {
+      const { bumpedContent } = bumpPackageVersion(
+        simpleContent,
+        '0.0.1',
+        'prerelease',
+      );
+
+      const project = new XmlDocument(bumpedContent!);
+      expect(project.valueWithPath('version')).toBe('0.0.2-SNAPSHOT');
+    });
+
     it('bumps pom.xml version with prerelease semver level', () => {
       const { bumpedContent } = bumpPackageVersion(
         prereleaseContent,

lib/modules/manager/maven/update.ts

@@ -1,3 +1,4 @@
+import is from '@sindresorhus/is';
 import semver, { ReleaseType } from 'semver';
 import { XmlDocument } from 'xmldoc';
 import { logger } from '../../../logger';
@@ -78,7 +79,31 @@ export function bumpPackageVersion(
     const startTagPosition = versionNode.startTagPosition;
     const versionPosition = content.indexOf(versionNode.val, startTagPosition);
 
-    const newPomVersion = semver.inc(currentValue, bumpVersion);
+    let newPomVersion: string | null = null;
+    const currentPrereleaseValue = semver.prerelease(currentValue);
+    if (isSnapshot(currentPrereleaseValue)) {
+      // It is already a SNAPSHOT version.
+      // Therefore the same qualifier (prerelease) will be used as before.
+      let releaseType = bumpVersion;
+      if (!bumpVersion.startsWith('pre')) {
+        releaseType = `pre${bumpVersion}` as ReleaseType;
+      }
+      newPomVersion = semver.inc(
+        currentValue,
+        releaseType,
+        currentPrereleaseValue!.join('.'),
+        false,
+      );
+    } else if (currentPrereleaseValue) {
+      // Some qualifier which is not a SNAPSHOT is present.
+      // The expected behaviour in this case is unclear and the standard increase will be used.
+      newPomVersion = semver.inc(currentValue, bumpVersion);
+    } else {
+      // A release version without any qualifier is present.
+      // Therefore the SNAPSHOT qualifier will be added if a prerelease is requested.
+      // This will do a normal increment, ignoring SNAPSHOT, if a non-prerelease bumpVersion is configured
+      newPomVersion = semver.inc(currentValue, bumpVersion, 'SNAPSHOT', false);
+    }
     if (!newPomVersion) {
       throw new Error('semver inc failed');
     }
@@ -108,3 +133,10 @@ export function bumpPackageVersion(
   }
   return { bumpedContent };
 }
+
+function isSnapshot(
+  prerelease: ReadonlyArray<string | number> | null,
+): boolean {
+  const lastPart = prerelease?.at(-1);
+  return is.string(lastPart) && lastPart.endsWith('SNAPSHOT');
+}