Summary

This PR adds the listLibrariesMissingMetadata Gradle task and the native:list-libraries-missing-metadata Maven goal. They scan a project's direct external runtime dependencies, classify each as supported or missing against the configured GraalVM reachability metadata repository, look up existing GitHub issues for the missing ones, and either print a prefilled issue link per library or (with createIssues=true) file the issues directly. Implements #871.

What Changed

New commands

• Gradle task listLibrariesMissingMetadata, registered in NativeImagePlugin and wired against the runtime classpath.
• Maven goal native:list-libraries-missing-metadata (requiresDependencyResolution=RUNTIME).
• Opt-in createIssues=true parameter on both that switches from "print prefilled link" to "file the issue via the GitHub API".
• Both commands always re-run (Gradle task uses upToDateWhen(false); Maven goal has no caching anyway).

Detection

• Shared MissingMetadataCommandSupport in common/graalvm-reachability-metadata is the single source of truth for classification; both plugins feed it DependencyCoordinates and consume a Report.
• A library is "missing" when the configured metadata repository returns no configurations for group:artifact:version, with the existing useLatestConfigWhenVersionIsUntested behavior preserved.
• Excluded modules from the metadata-repo extension are honored on both sides.
• Gradle selection: first-level ResolvedDependencyResults on the runtime classpath whose component is a ModuleComponentIdentifier (project components and unresolved entries are filtered out).
• Maven selection: artifacts with dependencyTrail.size() == 2 and scope compile / runtime / null.

GitHub integration

• Existing issues are looked up via the GitHub Search API filtered by repo:, is:issue is:open, label:library-new-request, and the groupId:artifactId substring; the result is matched by re-extracting coordinates from the issue title and body.
• Token resolution order is now: explicit (-PgithubToken=... / -DgithubToken=...) → GITHUB_TOKEN → GH_TOKEN → gh auth token (5-second subprocess; non-zero exit treated as no token).
• Default issue target repository is oracle/graalvm-reachability-metadata (was a personal fork).
• In default list mode, GitHub lookup failures (rate-limit, network, auth) emit a single throttled warning via the build tool's logger rather than silently producing false negatives. With createIssues=true the failure is fatal.
• The "missing token" validation error names the right argument per build tool (-PgithubToken=... for Gradle, -DgithubToken=... for Maven) and mentions all four token sources.

Console output

• Results are grouped by status: Already requested (existing open issues), Requested support for N libraries (when createIssues=true succeeded), and Or request support manually (the remaining ones). Errors get their own block at the bottom.
• A prominent call-to-action above the manual list shows the exact createIssues=true re-run command tailored to the build tool, plus the token-resolution order on the next line.
• Prefilled issue URLs collapse to numbered footnotes ([1], [E1], [C1]) so library names line up vertically instead of drowning in 200-character URLs.
• Prefilled issue links keep colons readable in the title= value and populate the issue form's maven_coordinates field so GitHub can auto-fill the request.
• All-supported runs collapse to a single sentence.
• A Full report: <path> footer points the user at the JSON report.

JSON report

• Stable schema matching the spec: command, mode, targetRepository, metadataRepositoryUri, scannedAt, project, summary, results[]. Per-result fields: coordinates, scope, status, plus issueStatus / issueUrl / issueNumber for missing entries and error for errors.
• Added versioned schema schemas/list-libraries-missing-metadata-schema-v1.0.0.json; generated reports now include a $schema field pointing to it.
• Default report file: build/reports/native/list-libraries-missing-metadata.json (Gradle), ${project.build.directory}/native/list-libraries-missing-metadata.json (Maven).

Configuration & wiring

• Gradle properties accepted by the task: createIssues, githubToken, targetRepository, githubApiUrl, reportFile (the last one is now actually wired up).
• Maven @Parameters with the same property names.
• getRootComponent() on the Gradle task is @Internal (paired with upToDateWhen(false)) for configuration-cache compatibility.

Tests

• MissingMetadataCommandSupportTest (shared) covers issue-title-and-body coordinate parsing, supported-vs-missing classification with prefilled-link generation, existing-issue reuse with group:artifact-level dedup (verified via an in-process HttpServer), token-resolution priority, the GitHub-CLI fallback, and the per-build-tool "missing token" error message. Tests of the new console layout assert on the headline, the call-to-action command, the token-resolution line, footnote indices, the prefilled issue-form URL, and the $schema report field.
• ListLibrariesMissingMetadataTest (Gradle) covers the dependency-selection contract: only direct external module dependencies survive, project components and unresolved entries are filtered, transitive children are not walked.
• ListLibrariesMissingMetadataMojoTest (Maven) covers isDirectRuntimeDependency across scope (compile/runtime/null/test/provided) and trail length (1/2/3/null).
• All of the above run as plain unit/Spock tests with no GitHub access required.
• An early-stage attempt at plugin-level functional tests was removed during iteration on this branch because it depended on specific libraries remaining unsupported in the live metadata repository; the unit/Spock coverage above replaces it.

Documentation

• gradle-plugin.adoc and maven-plugin.adoc get a "Checking Missing Metadata Support" reference section, including default usage, the createIssues=true opt-in, the report file location, the override properties, and the four-step token-resolution order.
• The end-to-end Gradle and Maven guides mention the command as the first troubleshooting step before tracing-agent workflows.
• The top-level docs intro carries a [TIP] callout pointing at the command.

Console output examples

Default mode (Gradle), all libraries missing, no existing requests

Missing metadata libraries: 3 of 3 scanned.

To request support for all 3 libraries automatically, re-run with createIssues=true:

    ./gradlew listLibrariesMissingMetadata -PcreateIssues=true -PgithubToken=<token>

  Token sources tried in order:
    -PgithubToken=...  ->  $GITHUB_TOKEN  ->  $GH_TOKEN  ->  `gh auth token`

Or request support manually, one library at a time:
  - commons-io:commons-io:2.16.1             -> request support [1]
  - org.apache.commons:commons-lang3:3.14.0  -> request support [2]
  - org.jsoup:jsoup:1.18.3                   -> request support [3]

  [1] https://github.com/oracle/graalvm-reachability-metadata/issues/new?template=01_support_new_library.yml&title=Support+for+commons-io:commons-io:2.16.1
  [2] https://github.com/oracle/graalvm-reachability-metadata/issues/new?template=01_support_new_library.yml&title=Support+for+org.apache.commons:commons-lang3:3.14.0
  [3] https://github.com/oracle/graalvm-reachability-metadata/issues/new?template=01_support_new_library.yml&title=Support+for+org.jsoup:jsoup:1.18.3

Full report: build/reports/native/list-libraries-missing-metadata.json

Default mode (Maven)

Same shape; the call-to-action becomes:

To request support for all 3 libraries automatically, re-run with createIssues=true:

    ./mvnw native:list-libraries-missing-metadata -DcreateIssues=true -DgithubToken=<token>

  Token sources tried in order:
    -DgithubToken=...  ->  $GITHUB_TOKEN  ->  $GH_TOKEN  ->  `gh auth token`

Mixed: some already requested, some still need support

Missing metadata libraries: 3 of 5 scanned (1 already requested).

Already requested (no action needed):
  - org.example:lib-x:1.0.0  -> existing request [E1]

To request support for the remaining 2 libraries automatically, re-run with createIssues=true:

    ./gradlew listLibrariesMissingMetadata -PcreateIssues=true -PgithubToken=<token>

  Token sources tried in order:
    -PgithubToken=...  ->  $GITHUB_TOKEN  ->  $GH_TOKEN  ->  `gh auth token`

Or request support manually, one library at a time:
  - com.acme:client:2.3.4   -> request support [1]
  - org.jsoup:jsoup:1.18.3  -> request support [2]

  [E1] https://github.com/oracle/graalvm-reachability-metadata/issues/4123
  [1]  https://github.com/oracle/graalvm-reachability-metadata/issues/new?template=01_support_new_library.yml&title=Support+for+com.acme:client:2.3.4
  [2]  https://github.com/oracle/graalvm-reachability-metadata/issues/new?template=01_support_new_library.yml&title=Support+for+org.jsoup:jsoup:1.18.3

Full report: build/reports/native/list-libraries-missing-metadata.json

After createIssues=true succeeds

Missing metadata libraries: 3 of 3 scanned.

Requested support for 3 libraries:
  - commons-io:commons-io:2.16.1             -> request created [C1]
  - org.apache.commons:commons-lang3:3.14.0  -> request created [C2]
  - org.jsoup:jsoup:1.18.3                   -> request created [C3]

  [C1] https://github.com/oracle/graalvm-reachability-metadata/issues/4201
  [C2] https://github.com/oracle/graalvm-reachability-metadata/issues/4202
  [C3] https://github.com/oracle/graalvm-reachability-metadata/issues/4203

Full report: build/reports/native/list-libraries-missing-metadata.json

All direct dependencies supported

All 6 direct dependencies are supported by the reachability metadata repository.

Full report: build/reports/native/list-libraries-missing-metadata.json

Verification

• Pushed this branch to origin as jormundur00/gh-871.
• Ran the affected modules' tests under JDK 17: :graalvm-reachability-metadata:test, :native-gradle-plugin:test, :native-maven-plugin:test — all pass, including the new dependency-selection unit tests and the updated console-rendering assertions.

Fixes: #871