What causes "Problem id parent must not be null" in gradle/gradle?

Pass an existing ProblemGroup, e.g. new DefaultProblemId('name', 'display', new DefaultProblemGroup('group', 'Group display'))

gradle/gradle · error · IllegalArgumentException

Problem id parent must not be null

Error message

Problem id parent must not be null

What it means

DefaultProblemId's constructor requires a non-null parent ProblemGroup; every problem ID belongs to a group (the group provides context and grouping in reports). A null parent leaves the ID unattached, so validateFields throws IllegalArgumentException('Problem id parent must not be null').

Source

Thrown at platforms/ide/problems-api/src/main/java/org/gradle/api/problems/internal/DefaultProblemId.java:48

    private final String displayName;
    private final ProblemGroup parent;

    public DefaultProblemId(String name, String displayName, ProblemGroup parent) {
        validateFields(name, displayName, parent);
        this.name = TextUtil.replaceLineSeparatorsOf(name, "");
        this.displayName = TextUtil.replaceLineSeparatorsOf(displayName, "");
        this.parent = parent;
    }

    private static void validateFields(String name, String displayName, ProblemGroup parent) {
        if (TextUtil.isBlank(name)) {
            throw new IllegalArgumentException("Problem id name must not be blank");
        }
        if (TextUtil.isBlank(displayName)) {
            throw new IllegalArgumentException("Problem id displayName must not be blank");
        }
        if (parent == null) {
            throw new IllegalArgumentException("Problem id parent must not be null");
        }
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public String getDisplayName() {
        return displayName;
    }

    @Override
    public ProblemGroup getGroup() {
        return parent;
    }

View on GitHub (pinned to 534f27719b)

Solutions

Pass an existing ProblemGroup, e.g. new DefaultProblemId('name', 'display', new DefaultProblemGroup('group', 'Group display'))
If the group is looked up, fail with a clear message when the lookup returns null instead of passing null through
Use the public problems API where groups are created and attached for you

Example fix

// before
ProblemId id = new DefaultProblemId("parse-error", "Parse error", findGroup(groupId)); // returns null -> throws

// after
ProblemGroup group = findGroup(groupId);
if (group == null) throw new IllegalArgumentException("Unknown problem group: " + groupId);
ProblemId id = new DefaultProblemId("parse-error", "Parse error", group);

Defensive patterns

Strategy: validation

Validate before calling

// Java: null-check the parent before constructing
ProblemGroup group = findGroup(groupId);
if (group == null) {
    throw new IllegalArgumentException("Unknown problem group id: " + groupId);
}
ProblemId id = new DefaultProblemId("name", "display", group);

Prevention

Resolve the parent group first and fail with its identifier if missing
Create the group before the ID in registration code
Avoid APIs where the parent is optional in your own wrappers

When it happens

Trigger: Constructing new DefaultProblemId("name", "displayName", null); passing a group variable that was never assigned; a factory method that forgets the group argument.

Common situations: Copy-pasted ID construction with the group parameter dropped; group lookup (e.g. from a registry) returning null for an unknown key; older code migrated from APIs where parent was optional.

Related errors

AI-assisted analysis of gradle/gradle@534f27719b (2026-08-22). Data as JSON: /api/errors/e6ac4351afd9799e. Report an issue: GitHub.