angular/angular-cli · error · Error

Project name already exists.

Error message

Project name already exists.

What it means

WorkspaceDefinition.add() enforces unique project names. Before creating the ProjectDefinition it checks the underlying DefinitionCollection via has(name) and throws if a project with that name is already registered. Duplicate project names make angular.json targets/paths ambiguous, so the collection rejects them eagerly.

Source

Thrown at packages/angular_devkit/core/src/workspace/definitions.ts:150

export class ProjectDefinitionCollection extends DefinitionCollection<ProjectDefinition> {
  constructor(
    initial?: Record<string, ProjectDefinition>,
    listener?: DefinitionCollectionListener<ProjectDefinition>,
  ) {
    super(initial, listener);
  }

  add(definition: {
    name: string;
    root: string;
    sourceRoot?: string;
    prefix?: string;
    targets?: Record<string, TargetDefinition | undefined>;
    [key: string]: unknown;
  }): ProjectDefinition {
    if (this.has(definition.name)) {
      throw new Error('Project name already exists.');
    }
    this._validateName(definition.name);

    const project: ProjectDefinition = {
      root: definition.root,
      prefix: definition.prefix,
      sourceRoot: definition.sourceRoot,
      targets: new TargetDefinitionCollection(),
      extensions: {},
    };

    if (definition.targets) {
      for (const [name, target] of Object.entries(definition.targets)) {
        if (target) {
          project.targets.set(name, target);
        }
      }
    }

View on GitHub (pinned to bb72145f9a)

Solutions

1. Check workspace.has(name) before adding and reuse/update the existing project instead.
2. Generate a unique name (suffix the app name) when adding programmatically.
3. Use set() or remove the existing project first if replacement is intended.

Example fix

// before
const project = workspace.addProject({ name: 'shared-ui', root: 'libs/shared-ui' });
// after
if (!workspace.has('shared-ui')) {
  const project = workspace.addProject({ name: 'shared-ui', root: 'libs/shared-ui' });
}

if (workspace.has(name)) {
  throw new Error(`Project '${name}' already exists in workspace`);
}
const project = workspace.addProject({ name, root });

function canAddProject(ws: WorkspaceDefinition, name: string): boolean {
  return typeof name === 'string' && !ws.has(name);
}

try {
  project = workspace.addProject({ name, root });
} catch (e) {
  if (e.message === 'Project name already exists.') {
    project = workspace.getProject(name); // reuse existing
  } else throw e;
}

When it happens

Trigger: Calling workspace.addProject({ name: 'my-app', root: '...' }) (or similar add) when a project named 'my-app' already exists in the WorkspaceDefinition.

Common situations: Generator/schematic run twice on the same workspace; programmatic script adding projects in a loop without deduplication; case is significant, but identical names from re-running code generation collide.

Related errors

• Target name already exists.
• "${name}" must be a JSON value.
• Project name must be a valid npm package name.
• Target name must be a string.
• Unable to read workspace file.

AI-assisted analysis of angular/angular-cli@bb72145f9a (2026-08-30). Data as JSON: /api/errors/ed59e489f947d8f1. Report an issue: GitHub.