# Migrate a Deprecated API Across Every Callsite in Angular with Atlas in 2026

> Atlas provides Angular developers with a systematic workflow to migrate deprecated APIs across an entire codebase, ensuring every callsite is updated and validated using `lsp`, `todowrite`

Migrating a deprecated API across an entire Angular codebase in 2026 requires a robust, systematic approach to ensure every callsite is updated and validated, a task Atlas excels at by integrating directly with your Angular toolchain. Atlas leverages its `lsp` tool to enumerate all usages, creates trackable `todowrite` entries for each, and applies changes with `apply_patch`, all while validating with `ng test` and formatting with `prettier` through `bash` commands, ensuring a complete and correct migration without manual oversight.

## Key takeaways

- Atlas uses `lsp findReferences` and `grep` to comprehensively enumerate all deprecated API calls in Angular projects.
- Every migration task is tracked with `todowrite`, providing granular progress visibility across your Angular codebase.
- Changes are applied safely with `apply_patch`, which validates context and prevents misapplication to drifted Angular files.
- Atlas integrates `ng test` via `bash` to validate each file migration, ensuring functional correctness in your Angular application.
- Unified diffs and git patch snapshots provide robust review and rollback capabilities for all Angular code modifications.

## How does Atlas find all deprecated API calls in an Angular project?

In 2026, Atlas precisely identifies every callsite of a deprecated Angular API by combining advanced code indexing with language server capabilities. It uses the `lsp` tool's `findReferences` operation, which queries the Angular Language Service to yield a complete and accurate list of all symbol usages across your `src/app` modules and components.

Atlas begins a deprecated API migration by thoroughly enumerating all existing callsites within your Angular project. It achieves this by leveraging its `lsp` tool, which connects to the underlying language server (like the Angular Language Service) to perform a `findReferences` operation on the deprecated symbol. This method is superior to simple text searches because it understands the code's structure, including imports, exports, and dependency injection, ensuring that all semantic usages are captured, even those in dynamically loaded modules or template files. After the initial `lsp` scan, Atlas cross-checks with its `grep` tool for any dynamic or string-based usages that might not be caught by the language server, providing a comprehensive enumeration. This dual approach guarantees that no callsite in your `src/app` directory, `environments` folder, or any other Angular-specific file is overlooked, setting a solid foundation for the migration.

## How does Atlas track migration progress across hundreds of Angular files?

Atlas manages the migration of hundreds of Angular files by creating a `todowrite` entry for each identified callsite, providing granular visibility into progress. This ensures that partial work is always visible and no individual migration step is silently skipped, offering a clear roadmap for the entire refactoring process in 2026.

Once Atlas has enumerated all callsites of the deprecated Angular API, it transforms this list into a series of trackable tasks using the `todowrite` tool. For every unique callsite identified by `lsp findReferences`, Atlas generates a distinct `todowrite` entry. This approach is crucial for large Angular codebases, where a single deprecated function might be used across dozens or even hundreds of components, services, and modules within `src/app`. Each `todowrite` entry represents a specific migration task, allowing developers to see exactly which files and lines still require attention. As Atlas processes each callsite, it updates the status of the corresponding `todowrite` entry, providing real-time progress updates. This visibility prevents 'silent skips' and ensures that even if the process is interrupted, the exact state of the migration is preserved, making it easy to resume work without losing context or missing any Angular-specific file like `my-component.ts` or `my-service.spec.ts`.

## How does Atlas safely apply changes and validate them with `ng test` in Angular?

Atlas applies changes to Angular files using context-anchored patches via `apply_patch`, ensuring edits are precise and fail safely if the file drifts. After each file modification, Atlas immediately runs `ng test` through its `bash` tool to validate the changes, marking the `todowrite` entry complete only upon successful test execution in 2026.

Atlas prioritizes safety and correctness when migrating deprecated APIs in Angular. For each callsite, it generates a specific patch that is applied using the `apply_patch` tool. This tool is designed to be robust: it seeks the hunk's context and `old_lines` within the target file (e.g., `src/app/feature/my-component.ts`). If the expected lines or context have drifted due to other concurrent changes, `apply_patch` will throw a 'Failed to find expected lines' error rather than guessing or misapplying the patch. This prevents silent corruption of your Angular codebase. Immediately after a patch is successfully applied to a file, Atlas executes the relevant tests using its `bash` tool, specifically `ng test --watch=false --include='src/app/path/to/affected.spec.ts'`. Only when these Angular tests pass does Atlas mark the corresponding `todowrite` entry as completed. This tight feedback loop ensures that each migration step is validated against your existing test suite, maintaining code quality and preventing regressions in your Angular application.

## What are Atlas's safety and review mechanisms for Angular code changes?

Atlas incorporates multiple safety and review mechanisms for Angular code changes, including permission-gated tool calls and a read-only planning agent. Every proposed edit generates a unified diff for approval, and changes are snapshotted as git patches, allowing easy rollback if issues arise during a 2026 migration.

Atlas is built with a strong emphasis on safety and developer control, crucial for large-scale Angular refactorings. Before any tool call, such as `lsp`, `grep`, or `apply_patch`, Atlas consults permission-gated `allow`, `ask`, and `deny` rules, ensuring that operations are only performed with explicit consent. The agent first drafts a comprehensive plan in a read-only plan agent, which you review and approve before it switches to a build agent to execute changes. For every file edit, Atlas computes a unified diff, which is presented to you for explicit approval before it's written to disk. This allows you to inspect every line change in `src/app/my-service.ts` or `angular.json` before it becomes permanent. Furthermore, Atlas reads git branches, status, and diffs, and can stage and create commits on your behalf. It also snapshots file changes as git patches, providing a robust rollback mechanism. If a change introduces an unexpected issue, you can easily revert to a previous state, ensuring confidence during complex Angular migrations.

## How does Atlas integrate with standard Angular development tools like `prettier` and `pnpm`?

Atlas direct integrates with standard Angular development tools like `prettier` for formatting and `pnpm` for package management. By leveraging its `bash` tool, Atlas can execute any command-line utility, ensuring that code changes adhere to your project's `prettier` configuration and that `pnpm` dependencies are correctly managed throughout the migration process in 2026.

Atlas is designed to fit into your existing Angular development workflow without requiring you to abandon your preferred tools. Through its `bash` tool, Atlas can execute any command-line utility, including `prettier` for code formatting and `pnpm` for managing project dependencies. For instance, after applying a patch to an Angular component file (e.g., `src/app/shared/button/button.component.ts`), Atlas can automatically run `pnpm exec prettier --write src/app/shared/button/button.component.ts` to ensure the new code adheres to your project's formatting standards defined in `.prettierrc.json`. Similarly, if the migration involves updating a dependency or installing a new package, Atlas can execute `pnpm install` or `pnpm add <package>` as part of its workflow. This deep integration means that Atlas not only performs the core migration but also ensures that the resulting codebase remains consistent, correctly formatted, and has its dependencies properly managed, just as you would expect from any Angular developer in 2026.

## Steps

1. 1. Initialize Atlas in your Angular workspace by running `atlas` in the directory containing your `angular.json` file, allowing it to read your modules, components, and dependency injection setup.
2. 2. Use Atlas's `lsp` tool to `findReferences` for the deprecated symbol (e.g., `atlas lsp findReferences --symbol 'DeprecatedService.oldMethod'`) to enumerate all callsites in your Angular project.
3. 3. Cross-check the `lsp` results with `atlas grep 'DeprecatedService.oldMethod'` to catch any dynamic or string-based usages within your Angular files.
4. 4. Create a `todowrite` entry for each identified callsite using Atlas, ensuring every migration task is tracked and visible (e.g., `atlas todowrite add 'Migrate callsite in src/app/my-component/my-component.ts'`).
5. 5. For each `todowrite` entry, use Atlas's `apply_patch` tool to migrate the callsite, ensuring the patch is context-anchored and fails if the file has drifted.
6. 6. After each file migration, run `atlas bash 'ng test --watch=false --include="src/app/path/to/affected.spec.ts"'` to validate the changes with your Angular test runner.
7. 7. Once tests pass, run `atlas bash 'pnpm exec prettier --write src/app/path/to/affected.ts'` to format the modified Angular file according to your project's `prettier` configuration.
8. 8. Mark the `todowrite` entry as complete and repeat for all remaining callsites. Finally, `atlas grep 'DeprecatedSymbol'` to confirm zero remaining hits, then delete the old implementation.

## FAQ

### How does Atlas ensure it doesn't miss any deprecated API calls in my Angular project?

Atlas combines the `lsp` tool's `findReferences` operation, which leverages the Angular Language Service for semantic understanding, with a `grep` search for dynamic or string-based usages. This dual approach ensures comprehensive enumeration across all your Angular components, services, and modules.

### Can Atlas automatically run `ng test` after making changes to an Angular file?

Yes, Atlas can execute `ng test` using its `bash` tool. After applying a patch to an Angular file, Atlas runs `ng test --watch=false --include='src/app/path/to/affected.spec.ts'` to validate the changes, only marking the task complete if tests pass.

### What happens if Atlas tries to apply a patch to an Angular file that has changed since enumeration?

Atlas's `apply_patch` tool is designed for safety. It uses context-anchored patches that require the `old_lines` to match the current file content. If the target Angular file (e.g., `src/app/my-component.ts`) has drifted, `apply_patch` will fail rather than misapplying the change, preventing silent code corruption.

### How does Atlas integrate with `prettier` for code formatting in Angular projects?

Atlas integrates with `prettier` through its `bash` tool. After a code change, Atlas can execute `pnpm exec prettier --write <file_path>` to automatically format the modified Angular file according to your project's `.prettierrc.json` configuration, maintaining code style consistency.

### Does Atlas provide a way to review and approve changes before they are written to my Angular codebase?

Absolutely. Atlas operates with a read-only plan agent for initial planning and computes a unified diff for every proposed file edit. You must explicitly approve this diff before Atlas writes any changes to your Angular files, giving you full control over the migration.

### Can Atlas help manage `pnpm` dependencies during an Angular API migration?

Yes, Atlas can manage `pnpm` dependencies. Its `bash` tool allows it to execute any `pnpm` command, such as `pnpm install` or `pnpm add <package>`, if the API migration requires updating or adding new dependencies to your Angular project.

### What Angular-specific files and configurations does Atlas understand?

Atlas is designed to work within an Angular workspace containing an `angular.json` file. It reads your modules, components, and dependency injection setup, understanding the structure of your `src/app` directory, `environments`, and other Angular-specific configurations.

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Canonical HTML: https://runatlas.sh/resources/stacks/migrate-a-deprecated-api-across-callsites-in-angular
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Licence: Atlas is proprietary with a free core. It is not open source and there is no public source repository.