[I] maven-resources-plugin NoSuchFileException when copying resources with targetPath [maven]

["gnodet (via GitHub)" <gi...@apache.org>]

gnodet opened a new issue, #12306:
URL: https://github.com/apache/maven/issues/12306

   ## Description
   
   Building `tomcat-taglibs-rdc` with Maven from the `maven-4.0.x` branch causes `maven-resources-plugin:3.3.1` to fail with a `NoSuchFileException` when copying resource files that use `<targetPath>`.
   
   The same build succeeds with Maven 3.x.
   
   ## Error
   
   ```
   [ERROR] Failed to execute goal
     org.apache.maven.plugins:maven-resources-plugin:3.3.1:resources (default-resources)
     on project taglibs-rdc:
     copying .../src/main/resources/org/apache/taglibs/rdc/resources/RDCBundle_en_US.properties
     to /org/apache/taglibs/rdc/resources/RDCBundle_en_US.properties
     failed with NoSuchFileException -> [Help 1]
   ```
   
   Note the target path starts with `/org/apache/...` — this appears to be a `<targetPath>` configuration in the resource definition. Maven 4 may be resolving the target path differently, causing the directory to not exist when the copy is attempted.
   
   ## Reproducer
   
   ```bash
   git clone https://github.com/apache/tomcat-taglibs-rdc.git
   cd tomcat-taglibs-rdc
   mvn -B -e clean package -DskipTests
   ```
   
   ## Environment
   
   - Maven: built from `maven-4.0.x` branch (bootstrapped with 4.0.0-rc-5)
   - JDK: 17 (Temurin)
   
   ## Context
   
   Found during [Maven 4 compatibility testing](https://github.com/gnodet/maven4-testing/issues/20677).
   
   _Claude Code on behalf of Guillaume Nodet_


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Re: [I] maven-resources-plugin NoSuchFileException when copying resources with targetPath [maven]

["gnodet (via GitHub)" <gi...@apache.org>]

gnodet closed issue #12306: maven-resources-plugin NoSuchFileException when copying resources with targetPath
URL: https://github.com/apache/maven/issues/12306


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Re: [I] maven-resources-plugin NoSuchFileException when copying resources with targetPath [maven]

["gnodet (via GitHub)" <gi...@apache.org>]

gnodet commented on issue #12306:
URL: https://github.com/apache/maven/issues/12306#issuecomment-4738562108

   ## Root Cause Analysis: `<targetPath>.</targetPath>` → empty string → absolute path at filesystem root
   
   ### The triggering config in `taglibs-rdc/pom.xml`
   
   ```xml
   <resource>
     <directory>src/main/resources</directory>
     <targetPath>.</targetPath>   <!-- a literal dot -->
   </resource>
   ```
   
   ### The bug chain (Maven 4 only)
   
   1. **`DefaultSourceRoot.java:111`** — constructor normalizes targetPath via Java NIO:
      ```java
      this.targetPathOrNull = (targetPathOrNull != null) ? targetPathOrNull.normalize() : null;
      ```
      `Path.of(".").normalize()` returns an **empty path** (zero name elements, `toString()=""`) because `.` is a redundant element. The result is **not null**, so it gets stored as a non-null empty Path.
   
   2. **`ConnectedResource.java:46`** — converts it to an empty string for the legacy plugin:
      ```java
      .targetPath(sourceRoot.targetPath().map(Path::toString).orElse(null))
      // → ""   (empty string, NOT null)
      ```
   
   3. **`DefaultMavenResourcesFiltering.getDestinationFile()`** — the plugin concatenates:
      ```java
      destination = "" + "/" + "org/apache/taglibs/rdc/resources/RDCBundle_en_US.properties"
                  = "/org/apache/taglibs/rdc/resources/RDCBundle_en_US.properties"  // absolute!
      ```
      Java's `File("/org/...").isAbsolute() == true`, so `outputDirectory` (`/project/target/classes`) is **completely bypassed**. Maven tries to write to the filesystem root → `NoSuchFileException`.
   
   ### Why Maven 3 worked
   
   Maven 3 passed the original `"."` string to the plugin without NIO normalization. The plugin computed `"." + "/" + filename = "./filename"` (relative), which was correctly resolved against the output directory.
   
   ### Fix location
   
   **`DefaultSourceRoot.java:111`** — treat empty normalized paths as null (same semantics as no targetPath):
   ```java
   if (targetPathOrNull != null) {
       Path normalized = targetPathOrNull.normalize();
       // "." normalizes to empty path = "copy to output root" = same as null
       this.targetPathOrNull = (normalized.getNameCount() == 0) ? null : normalized;
   } else {
       this.targetPathOrNull = null;
   }
   ```
   
   The existing test `testHandlesEmptyTargetPathFromResource` tests explicit `""` (handled by `nonBlank()` → null, never reaches the normalization path), but **there's no test for `"."` which takes a completely different code path**. A test for `targetPath="."` would have caught this.
   
   _Claude Code on behalf of Guillaume Nodet_


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