A security blanket for Xcode project files
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README.md

Xcode Project Linter (xcprojectlint)

Overview

This project provides a security blanket, ensuring neither your co-workers, nor git screw up your Xcode project file. Some of the settings are arguably a matter of personal taste. Fortunately, each option can be enabled separately. xcprojectlint currently supports these checks:

  • build-settings-externalized

    This mode ensures there are no settings configured at the project level, instead encouraging the use of xcconfig files.

  • disk-layout-matches-project

    This mode ensures the project references reflect actual file system locations. There are some occasions where you may not be able to exactly map a folder to disk (Frameworks and Products are common examples). For this, there is an additional parameter you can pass: --skip-folders, followed by a list of folders to ignore.

  • files-exist-on-disk

    This mode finds file references in the project which are not backed by files.

  • empty-groups

    This mode reports groups that contain no additional items.

  • items-in-alpha-order

    This mode ensures the project files and folders are in proper order.

  • all

    For convenience, this mode runs all of the above tests.

When a failing condition is detected, as much useful context as possible is emitted to STDOUT, enabling Xcode to display the errors, in place. Further, it optionally can return EX_SOFTWARE, preventing the build from succeeding until the problem is addressed.

Building the Code

To build xcprojectlint tool, run

$ swift package update
$ make build

Huh? A Makefile?!?

We’re using make to hide several shortcomings of the current state of Swift Package Manager. First off, it has no notion of Resources, which we need for our unit tests.

$ make test

to build the test target, copy in the test fixtures, then run the tests.

Second up, the static linking option is documented to be broken, and indeed, it is.

$ make release

passes the optional arguments that make static linked binaries actually happen.

For completeness, there are also wrappers for clean and build.

Debugging in Xcode

If you want to debug from Xcode, you can run make xcode to generate the project file, and then add a Copy Files build phase, configured like this:

Copy Bundle Resources

Usage Examples

as a build script phase:

bin/xcprojectlint --report error --validations all --project $PROJECT_FILE_PATH

as a shell command:

xcprojectlint --report error --validations files-exist-on-disk items-in-alpha-order
--project /tmp/Example/Example.xcproject

The Nitty Gritty

xcprojectlint is operating on an undocumented file format. Years of looking at broken git merges has given us a reasonable confidence that we know how the parts all work together. That said, it is still a best guess, so there may be oversights. Fortunately, these linting operations are read-only, and will not modify your project file.

Each run starts by parsing the project file into a series of collections, which represent our understanding of how a project file is composed. It uses both the property list structure, and the comments Xcode writes into the project to assemble its data. Afterwards, xcprojectlint applies validity tests to the extracted collections, ensuring that the rules specified are met.

Clues to Fix By

As much as possible, xcprojectlint will attempt to tell you how to locate the problem. It’ll tell you which build configuration has settings, what the expected order of a group is, and whatever else it can squeeze out of the available context. Sometimes, it’ll even tell you the line number in the project file to look at. This is great, but do not attempt to view the project within Xcode. Terrible, terrible things will happen. Instead, use your favorite text editor to peer inside.

The Rules

  • Build Settings Externalized

    We iterate all the BuildConfiguration blobs, and investigate their BuildSettings entry. Empty settings are A-OK. Any found settings are in error.

  • Disk Layout Matches Project

    This test grabs the MainGroup out of the project, then recursively traverses the children. If the child node is a file, we retrieve the FileReference by id, then check for a name value. The presence of a name indicates this file reference does not have a matching file on disk.

  • Files Exist on Disk

    This uses a similar recursion to the Layout test, but instead of investigating the name value, it builds a URL to where the file should appear on disk. This is done by assembling the path that led to the file, then appending that to a path derived from the project’s path on disk, then finally testing for the presence of a file at that location.

  • Empty Groups

    One of the simpler tests. We again recurse the MainGroup, but this time look for entries that have zero children.

  • Items in Alpha Order

    We expect our project nodes to contain alphabetized Folders, followed by alphabetized Files. We check on that by again recursing the groups, and at each level sifting the entries into groupNames, fileNames, and allNames. We sort the groups and files, contatenate them, then compare that to the list of everything.

Contributing

We welcome Your interest in the American Express Open Source Community on Github. Any Contributor to any Open Source Project managed by the American Express Open Source Community must accept and sign an Agreement indicating agreement to the terms below. Except for the rights granted in this Agreement to American Express and to recipients of software distributed by American Express, You reserve all right, title, and interest, if any, in and to Your Contributions. Please fill out the Agreement.

Please feel free to open pull requests and see CONTRIBUTING.md for commit formatting details.

License

Any contributions made under this project will be governed by the Apache License 2.0.

Code of Conduct

This project adheres to the American Express Community Guidelines. By participating, you are expected to honor these guidelines.