feats: extend ValuePool by new fields : files, and maxMutations #1033

oetr · 2026-01-21T12:37:45Z

The users can now supply glob patterns to the @ValuePool annotation by using the new field String[] files---files matching the patterns will be loaded as byte []. The field uses the glob: syntax of java.nio.file.PathMatcher.

Example:

@ValuePool(files={"src/test/resources/**", "/home/user/fuzzing-corpus/compression/zip/**"})

In addition, by setting the new field maxMutations, the users can now control up to how many times (by default 1) values selected from @ValuePool will be mutated by the underlying mutator in one mutation operation.

Copilot

Pull request overview

This PR extends the @ValuePool annotation to support two new capabilities: (1) loading files as byte arrays using glob patterns via a new files field, and (2) controlling mutation iterations via a new maxMutations field.

Changes:

Added files field to @ValuePool annotation for glob-based file loading
Added maxMutations field to control mutation iterations on pool values
Implemented file pattern matching and path resolution in ValuePoolRegistry
Updated mutation logic to apply multiple mutations based on maxMutations
Added caching for ArgumentsMutator instances and file reads
Comprehensive test coverage for file loading feature
Extensive documentation updates

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 16 comments.

Show a summary per file

File	Description
src/main/java/com/code_intelligence/jazzer/mutation/annotation/ValuePool.java	Added `files` and `maxMutations` fields to annotation with documentation
src/main/java/com/code_intelligence/jazzer/mutation/support/ValuePoolRegistry.java	Implemented glob pattern matching, file loading, and maxMutations extraction with path resolution logic
src/main/java/com/code_intelligence/jazzer/mutation/mutator/lang/ValuePoolMutatorFactory.java	Updated mutate/crossOver to apply multiple mutations based on maxMutations
src/test/java/com/code_intelligence/jazzer/mutation/support/ValuePoolsTest.java	Added comprehensive tests for file loading patterns and updated test helpers
src/main/java/com/code_intelligence/jazzer/mutation/ArgumentsMutator.java	Added caching for ArgumentsMutator instances to improve performance
src/main/java/com/code_intelligence/jazzer/junit/FuzzTestExecutor.java	Set system property for baseDir to enable ValuePoolRegistry file resolution
docs/mutation-framework.md	Added extensive documentation for ValuePool features including examples and usage patterns

Comments suppressed due to low confidence (1)

src/test/java/com/code_intelligence/jazzer/mutation/support/ValuePoolsTest.java:415

The test helper withValuePoolImplementation is missing the maxMutations() method implementation. Since maxMutations() is now part of the @valuepool annotation interface, this anonymous implementation must override it. Without this method, using this test helper will result in runtime errors when the annotation's maxMutations() method is called.

    return new ValuePool() {
      @Override
      public String[] value() {
        return value;
      }

      @Override
      public String[] files() {
        return files;
      }

      @Override
      public double p() {
        return p;
      }

      @Override
      public String constraint() {
        return constraint;
      }

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docs/mutation-framework.md

src/main/java/com/code_intelligence/jazzer/mutation/support/ValuePoolRegistry.java

src/main/java/com/code_intelligence/jazzer/mutation/annotation/ValuePool.java

src/main/java/com/code_intelligence/jazzer/mutation/support/ValuePoolRegistry.java

src/test/java/com/code_intelligence/jazzer/mutation/support/ValuePoolsTest.java

src/main/java/com/code_intelligence/jazzer/mutation/mutator/lang/ValuePoolMutatorFactory.java

docs/mutation-framework.md

src/main/java/com/code_intelligence/jazzer/mutation/support/ValuePoolRegistry.java

src/main/java/com/code_intelligence/jazzer/mutation/mutator/lang/ValuePoolMutatorFactory.java

Copilot

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 9 comments.

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src/test/java/com/code_intelligence/jazzer/mutation/support/ValuePoolsTest.java

src/main/java/com/code_intelligence/jazzer/mutation/support/ValuePoolRegistry.java

docs/mutation-framework.md

src/test/java/com/code_intelligence/jazzer/mutation/support/ValuePoolsTest.java

src/main/java/com/code_intelligence/jazzer/mutation/mutator/lang/ValuePoolMutatorFactory.java

src/main/java/com/code_intelligence/jazzer/junit/FuzzTestExecutor.java

The number of fields in ValuePool is getting large, so that construction using positional args is becoming confusing. Using a builder simplifies the tests.

Don't generate the same mutator for the same fuzz test method multiple times. Before this change, a mutator was generated for each crash file in fuzzing mode.

Marcono1234

Hopefully these comments are useful. Feel free to consider them only as suggestions or ignore them completely.

Please let me know if these comments are not useful or if you consider them disruptive.

Marcono1234 · 2026-01-22T18:28:48Z

docs/mutation-framework.md

+    // - Integer mutator for Map values in 'foo'
+}
+
+static Stream mySupplier() {


To avoid raw types?

Suggested change

static Stream mySupplier() {

static Stream<?> mySupplier() {

Marcono1234 · 2026-01-22T18:29:09Z

docs/mutation-framework.md

+### Complete Example
+```java
+class MyFuzzTest {
+    static Stream edgeCases() {


To avoid raw types?

Suggested change

static Stream edgeCases() {

static Stream<?> edgeCases() {

Marcono1234 · 2026-01-22T18:30:16Z

docs/mutation-framework.md

+        return Stream.of(
+            "", "null", "alert('xss')",  // Strings
+            0, -1, Integer.MAX_VALUE,    // Integers
+            new byte[]{0x00, 0xFF},      // A byte array


Causes a compilation error because 0xFF is an int literal > Byte.MAX_VALUE. Maybe choose something else for simplicity (avoiding a (byte) cast)?

Suggested change

new byte[]{0x00, 0xFF}, // A byte array

new byte[]{0x00, 0x7F}, // A byte array

Marcono1234 · 2026-01-22T18:32:18Z

src/main/java/com/code_intelligence/jazzer/mutation/annotation/ValuePool.java

 public @interface ValuePool {
  /**
   * Specifies supplier methods that generate values for fuzzing the annotated method or type. The
   * specified supplier methods must be static and return a {@code Stream <?>} of values. The values


Suggested change

* specified supplier methods must be static and return a {@code Stream<?>} of values. The values

(redundant space between Stream and <?>)

Marcono1234 · 2026-01-22T18:34:22Z

src/main/java/com/code_intelligence/jazzer/mutation/annotation/ValuePool.java

+  String[] value() default {};
+
+  /**
+   * Specifies glob patterns matching files that should be provided as {@code byte []} to the


Redundant space? (or is that intentional?)

Suggested change

* Specifies glob patterns matching files that should be provided as {@code byte []} to the

* Specifies glob patterns matching files that should be provided as {@code byte[]} to the

Marcono1234 · 2026-01-22T18:46:23Z

src/main/java/com/code_intelligence/jazzer/mutation/support/ValuePoolRegistry.java

+      start = baseDir.toAbsolutePath().normalize();
+    } else { // absolute
+      if (Paths.get(prefix).isAbsolute()) {
+        start = Paths.get(prefix);


Shouldn't this consider lastSeparator here as well?

Suggested change

start = Paths.get(prefix);

start = Paths.get(prefix.substring(0, lastSeparator));

Or define a local variable for this to avoid duplicating this code, respectively just reassign prefix as prefix = prefix.substring(0, lastSeparator)?

I think the reason why this is not detected by the new unit tests is that they all create glob patterns where / is immediately followed by *, e.g. .../**.json. Maybe they should also do something like .../f*.json, that would probably trigger this bug.

Marcono1234 · 2026-01-22T18:48:08Z

src/main/java/com/code_intelligence/jazzer/mutation/support/ValuePoolRegistry.java

+      Path path = Paths.get(glob);
+      Path absolutePath =
+          path.isAbsolute() ? path : baseDir.toAbsolutePath().normalize().resolve(path);
+      return Files.isRegularFile(absolutePath) ? Stream.of(absolutePath) : Stream.empty();


General question for here and below: In case no matching files were found (or an IO error occurs), would it be better to report that as error? That would make troubleshooting for users easier, and they would notice sooner when they renamed / deleted a value pool folder without adjusting the corresponding paths in the fuzz test.

Marcono1234 · 2026-01-22T18:55:48Z

src/main/java/com/code_intelligence/jazzer/mutation/support/ValuePoolRegistry.java

+    } else {
+      lastSeparator = prefix.lastIndexOf('/');
+    }
+


FileSystem#getPathMatcher performs unescaping of \\. For consistency, would it therefore make sense to manually unescape it in prefix.substring(0, lastSeparator)? Otherwise it might be a bit inconsistent that in one part of the glob \ has to be escaped whereas in the other part it does not.

Note: It seems any character can be escaped, e.g. glob:a\b matches ab.

Marcono1234 · 2026-01-22T19:05:15Z

src/test/java/com/code_intelligence/jazzer/mutation/support/ValuePoolsTest.java

+    assertThat(
+            assertThrows(
+                    IllegalArgumentException.class, () -> valuePools.extractFirstMaxMutations(type))
+                .getMessage())
+        .contains("@ValuePool maxMutations must be >= 0");


Might be more idiomatic to use assertThat(...).hasMessageThat()..., instead of calling getMessage() manually?

Marcono1234 · 2026-01-22T19:07:00Z

src/test/java/com/code_intelligence/jazzer/mutation/support/ValuePoolsTest.java

-    assertThat(elements).isPresent();
-    assertThat(elements.get()).containsExactly("value1", "value2", "value3");
+    List<?> elements = valuePools.extractUserValues(type).collect(Collectors.toList());
+    assertThat(elements).isNotEmpty();


Maybe the isNotEmpty() followed by containsExactly(...) is redundant? Same also for the other test methods below.

(previously for Optional the isPresent() check made sense to avoid an exception when calling get())

Copilot AI review requested due to automatic review settings January 21, 2026 12:37

Copilot started reviewing on behalf of oetr January 21, 2026 12:38 View session

Copilot AI reviewed Jan 21, 2026

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oetr force-pushed the CIF-1907-add-glob-pattern-to-value-pool branch 4 times, most recently from ed09c59 to e2cc773 Compare January 21, 2026 19:08

oetr marked this pull request as draft January 21, 2026 19:08

oetr force-pushed the CIF-1907-add-glob-pattern-to-value-pool branch 2 times, most recently from 42a3a15 to 6d874ba Compare January 21, 2026 20:37

chore: increase test timeout for the selffuzz test

de56692

oetr force-pushed the CIF-1907-add-glob-pattern-to-value-pool branch from 6d874ba to 112ab04 Compare January 22, 2026 07:16

oetr marked this pull request as ready for review January 22, 2026 07:48

oetr requested review from a team and Copilot January 22, 2026 07:49

Copilot started reviewing on behalf of oetr January 22, 2026 07:49 View session

Copilot AI reviewed Jan 22, 2026

View reviewed changes

oetr added 5 commits January 22, 2026 12:06

chore: build ValuePool using a builder in tests

bbe5f01

The number of fields in ValuePool is getting large, so that construction using positional args is becoming confusing. Using a builder simplifies the tests.

feat: cache mutators and value pools for each method

3da5408

Don't generate the same mutator for the same fuzz test method multiple times. Before this change, a mutator was generated for each crash file in fuzzing mode.

feat: ValuePool can load files that match directory patterns

31c022e

feat: add configurable max number of mutations for ValuePools

581c515

feat: document @valuepool

49403fd

oetr force-pushed the CIF-1907-add-glob-pattern-to-value-pool branch from 112ab04 to 49403fd Compare January 22, 2026 14:38

Marcono1234 reviewed Jan 22, 2026

View reviewed changes

	new byte[]{0x00, 0xFF}, // A byte array
	new byte[]{0x00, 0x7F}, // A byte array


	* specified supplier methods must be static and return a {@code Stream<?>} of values. The values

	* Specifies glob patterns matching files that should be provided as {@code byte []} to the
	* Specifies glob patterns matching files that should be provided as {@code byte[]} to the

	start = Paths.get(prefix);
	start = Paths.get(prefix.substring(0, lastSeparator));

feats: extend ValuePool by new fields : files, and maxMutations #1033

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feats: extend ValuePool by new fields : files, and maxMutations #1033

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oetr commented Jan 21, 2026 •

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