java-topology/defects/maven/unit/MavenLifecycleStandardSetTest.java

package unit;

import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

/**
 * maven-0001 — DefaultLifecycleExecutionPlanCalculator: List.of().contains() rebuilt per mojo
 *
 * Demonstrates CWE-407: O(n) linear list membership inside a hot loop.
 *
 * slow(): models the defective path — List.of(STANDARD_LIFECYCLES).contains() called N times,
 *         allocating a new List and scanning it on every call.
 * fast(): models the fix — a precomputed Set<String> constant, O(1) per lookup.
 *
 * Asserts that slow() performs strictly more element comparisons than fast().
 */
public class MavenLifecycleStandardSetTest {

    static final String[] STANDARD_LIFECYCLES = {"clean", "default", "site"};

    /** Counts how many element comparisons the slow path performs for N lookups. */
    static long slow(String[] lifecycleIds) {
        long ops = 0;
        for (String id : lifecycleIds) {
            // Rebuild list and scan linearly — defective pattern
            List<String> list = Arrays.asList(STANDARD_LIFECYCLES);
            for (int i = 0; i < list.size(); i++) {
                ops++;
                if (list.get(i).equals(id)) break;
            }
        }
        return ops;
    }

    /** Counts how many element comparisons the fast path performs for N lookups. */
    static long fast(String[] lifecycleIds) {
        long ops = 0;
        // Precomputed constant set — the fix
        Set<String> standardSet = Collections.unmodifiableSet(
            new HashSet<>(Arrays.asList(STANDARD_LIFECYCLES)));
        for (String id : lifecycleIds) {
            ops++;  // HashSet.contains = 1 hash + at most 1 comparison
            standardSet.contains(id);
        }
        return ops;
    }

    public static void main(String[] args) {
        // Simulate M=200 modules × N=50 mojos = 10 000 calculateLifecycleMappings calls
        // Mix of matches and misses; worst case is always a miss (scans full list)
        int iterations = 10_000;
        String[] ids = new String[iterations];
        String[] pool = {"clean", "default", "site", "unknown-lifecycle", "custom"};
        for (int i = 0; i < iterations; i++) {
            ids[i] = pool[i % pool.length];
        }

        long sOps = slow(ids);
        long fOps = fast(ids);

        // Expect slow to do at least 2x the comparisons of fast
        int Nx = 2;
        boolean pass = sOps > fOps * Nx;
        System.out.printf("maven-0001: slow=%d ops  fast=%d ops  ratio=%.1fx  %s%n",
            sOps, fOps, (double) sOps / fOps, pass ? "PASS" : "FAIL");
        if (!pass) {
            System.exit(1);
        }
    }
}