In 2026, F# developers leverage Atlas to efficiently upgrade dependencies and resolve breaking changes. Atlas drives NuGet via `dotnet add package`, interprets `dotnet build` output, and fixes code with `edit`, ensuring `Expecto` tests pass and `fantomas` maintains code style.
How does Atlas upgrade F# NuGet packages?
In 2026, Atlas streamlines F# dependency upgrades by directly interacting with `NuGet` through `dotnet add package`. This process begins with Atlas executing the upgrade command via its `bash` tool, capturing all output, even if it exceeds terminal limits, to ensure no detail is missed.
Atlas initiates a dependency upgrade in an F# project by using its `bash` tool to run `dotnet add package` with the specified package and version. For instance, to upgrade a package like `FSharp.Core` or `Giraffe`, Atlas would execute a command such as `dotnet add package Giraffe --version 7.0.0`. Atlas is designed to operate within a solution containing an `.fsproj` file, which is crucial for F# as it compiles files in order. The `bash` tool captures the complete output of this command, including any warnings or initial errors, saving it to a file if it is too large for immediate display. This ensures that Atlas has a comprehensive record of the package manager's response, forming the first step in understanding the scope of the required fixes.
How does Atlas identify F# compile errors after a dependency upgrade?
Atlas identifies F# compile errors by directly invoking `dotnet build` via its `bash` tool, rather than guessing potential breakage. This approach, fundamental in 2026, ensures Atlas reads the real compiler output, enumerating every failure caused by the upgraded dependency.
After upgrading a `NuGet` package, Atlas uses its `bash` tool to run `dotnet build` on the F# project. This command triggers the F# compiler, which then enumerates all compile-time errors. Atlas reads this output directly, understanding the specific error messages, file paths (for example, `src/MyProject/Domain.fs`), and line numbers. This direct interaction with the F# toolchain means Atlas does not rely on predefined patterns but reacts to actual compiler feedback. Furthermore, if the upgrade involves a major version bump, Atlas can use `webfetch` to retrieve the library's release notes or changelog. This provides crucial context about breaking changes, allowing Atlas to formulate fixes that align with the library's actual migration guide, rather than making assumptions. Atlas also respects F# specific constructs like discriminated unions and computation expressions when analyzing the code.
How does Atlas fix F# code for breaking changes?
Atlas fixes F# code by employing its `edit` tool, guided by the `lsp` tool's `goToDefinition` operation to inspect new signatures in the upgraded package. This precise method, available in 2026, ensures fixes for F# constructs like discriminated unions or Option pipelines are accurate and context-aware.
When `dotnet build` reports an F# compile error, Atlas uses its `edit` tool to modify the problematic code. For each error, Atlas can leverage the `lsp` (Language Server Protocol) tool's `goToDefinition` operation. This allows Atlas to jump directly to the definition of the changed function or type within the newly upgraded `NuGet` package, inspecting its new signature or structure. For example, if a function signature in `Giraffe` has changed, Atlas can see the updated parameters and adjust the F# call site in files like `src/Web/Server.fs` accordingly. Atlas is specifically designed to understand F# idioms, such as replacing null checks with `Option` pipelines or correctly handling discriminated unions, ensuring that fixes are idiomatic and maintain F#’s functional style. Atlas also considers the file order specified in the `.fsproj` when making edits, which is critical for F# compilation.
How does Atlas ensure F# code quality and correctness during upgrades?
Atlas ensures F# code quality and correctness by iteratively running `dotnet build` and `dotnet test (Expecto)` until all failures are resolved. This rigorous process, a core Atlas capability in 2026, guarantees that every compile error and `Expecto` test failure is addressed before any changes are proposed.
After making edits to fix compile errors, Atlas re-runs `dotnet build` using its `bash` tool. This iterative process continues until the F# project compiles cleanly. Once compilation is successful, Atlas proceeds to run the tests using `dotnet test (Expecto)`. If any `Expecto` tests fail, Atlas analyzes the test output, identifies the root cause, and uses its `edit` tool to apply further fixes. This cycle of edit, build, and test repeats until both `dotnet build` and `dotnet test (Expecto)` report success. Finally, before presenting the changes for approval, Atlas runs `fantomas` over all modified `.fs` files. This ensures that the F# code adheres to the project's formatting standards, maintaining consistency and readability across the codebase.
What safety and review mechanisms does Atlas provide for F# dependency upgrades?
Atlas incorporates robust safety and review mechanisms for F# dependency upgrades, ensuring developer control in 2026. Every Atlas tool call, including `bash` commands for `NuGet` or `dotnet test (Expecto)`, is permission-gated, and all file edits are presented as a unified diff for explicit approval before writing.
Atlas prioritizes developer control and safety throughout the F# dependency upgrade process. Every tool call, whether it is `bash` for `dotnet add package` or `dotnet test (Expecto)`, `webfetch` for changelogs, or `edit` for code modifications, is permission-gated. This means Atlas will `ask` for permission before executing, or can be configured to `allow` or `deny` specific actions. Before any changes are written to disk, Atlas computes a unified diff for every modified F# file (for example, `src/Library.fs`, `tests/Library.Tests.fs`). This comprehensive diff is surfaced for the developer's approval, allowing a thorough review of all proposed changes. Atlas also reads `git` branches and status, and can stage and create commits on the developer's behalf, ensuring that the entire upgrade process is transparent and fully auditable. File changes are snapshotted as `git` patches, enabling easy rollback if needed.
Step by step
- 01Run `NuGet` upgrade: Atlas uses `bash` to execute `dotnet add package YourPackage --version X.Y.Z` and captures the full output.
- 02Fetch release notes: Atlas uses `webfetch` to retrieve the library's changelog or release notes for context on breaking changes.
- 03Build and identify F# errors: Atlas runs `bash` with `dotnet build` to compile the F# project and reads the specific compiler output for breakage.
- 04Fix F# code: Atlas uses `edit` and `lsp`'s `goToDefinition` to inspect new signatures and repair F# call sites in `.fs` files.
- 05Re-run build and tests: Atlas iteratively runs `bash` with `dotnet build` and `dotnet test (Expecto)` until all F# compile errors and test failures are resolved.
- 06Format F# code: Atlas runs `fantomas` over all changed `.fs` files to ensure consistent F# code style.
- 07Review and commit: Atlas presents a unified diff of all F# file changes for approval and can stage/commit the changes via `git`.
Frequently asked questions
- How does Atlas handle F# specific language features during upgrades?
- Atlas is designed to respect F# specific constructs like file order in `.fsproj`, discriminated unions, computation expressions, and `Option` pipelines, ensuring fixes are idiomatic.
- Can Atlas upgrade F# packages like `Giraffe` or `Fable`?
- Yes, Atlas can upgrade any `NuGet` package, including popular F# libraries like `Giraffe` or `Fable`, by driving `dotnet add package` and fixing resulting breakage.
- How does Atlas ensure my F# code style is maintained after fixes?
- After applying fixes, Atlas runs `fantomas` over all modified `.fs` files to automatically format the F# code according to your project's standards.
- What if an F# dependency upgrade requires a complex migration strategy?
- Atlas uses `webfetch` to retrieve release notes and changelogs, providing context for complex migrations. It then iteratively fixes errors, guided by the F# compiler and test runner, allowing for step-by-step resolution.
- Is Atlas safe to use for critical F# production codebases?
- Yes, Atlas operates with robust safety features. All tool calls are permission-gated, and every proposed change to F# files is presented as a unified diff for your explicit approval before being written.
- Does Atlas support F# test frameworks other than Expecto?
- While the context specifically mentions `Expecto` with `dotnet test`, Atlas interacts with the `bash` tool to run any command. If your F# project uses a different test runner, Atlas can execute its commands and interpret the output.
- How does Atlas know the file order for F# compilation?
- Atlas builds its code index by parsing the `.fsproj` file, which explicitly defines the file order for F# compilation. This ensures Atlas understands the project structure correctly.
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