FIDL Cross-Petal Change Tests

These are tests to validate source-compatibility through various changes to FIDL libraries. They do not test binary-compatibility. Tests for compiled languages are only meant to be built, not executed, since source-compatibility issues show up at compile time.

Transitions

Soft transitioning a FIDL library involves an initial state (before), an intermediate state (during), and a final state (after). Depending on the bindings used and the kind of change made to the FIDL library, the transition is either FIDL-assisted or source-assisted.

FIDL-assisted

In a FIDL-assisted transition, you change source code while the FIDL library is held in a transitional state (e.g., using the Transitional attribute). For these transitions, we test four states:

Source-assisted

In a source-assisted transition, you change the FIDL library while source code held is in a transitional state (e.g., using default: in switch statements). This would lead to testing four states:

However, certain FIDL changes require a FIDL-assisted transition in some bindings and a source-assisted transition in others. Suppose we make a change in FIDL library L requiring a FIDL-assisted transition in bindings A and source-assisted in bindings B. We would take the following steps:

1. Initially, L, A, and B are before.
2. Change B to during.
3. Change L to during.
4. Change A to after.
5. Change L to after.
6. Change B to after.

All correct ways of interleaving the steps will have L and B both in the during state at some point. Therefore, although a FIDL during state is unnecessary for a pure source-assisted transition, we must include it in tests. Thus, we actually test 5 states for source-assisted transitions:

Libraries

Under fidl/ there are three libraries:

• fidl.test.before, before the change has begun;
• fidl.test.during, during the transition;
• fidl.test.after, after the transition is complete.

Tests

C++

Under cpp/ there are four binary targets testing FIDL-assisted transitions:

• cpp_before compiles cpp/before.cc against fidl.test.before
• cpp_during_1 compiles cpp/before.cc against fidl.test.during
• cpp_during_2 compiles cpp/after.cc against fidl.test.during
• cpp_after compiles cpp/after.cc against fidl.test.after

There are currently no tests for C++ source-assisted transitions.

Go

Under go/ there is a single package testing FIDL-assisted transitions. The package has client code:

• client_1_before.go tests client code against fidl.test.before.
• client_2_before_during.go is generated by update-during.sh.
• client_3_after_during.go is generated by update-during.sh.
• client_4_after.go tests client code against fidl.test.after.

And server code:

• server_1_before.go tests server code against fidl.test.before.
• server_2_before_during.go is generated by update-during.sh.
• server_3_after_during.go is generated by update-during.sh.
• server_4_after.go tests server code against fidl.test.after.

There are currently no tests for Go source-assisted transitions.

Rust

Under rust/ there is a single library testing both FIDL-assisted transitions:

• fidl_assisted/main.rs executes macros from the other two modules.
• fidl_assisted/before.rs defines the macro before_impl.
• fidl_assisted/after.rs defines the macro after_impl.

And source-assisted transitions:

• source_assisted/main.rs executes macros from the other three modules.
• source_assisted/before.rs defines the macro before_impl.
• source_assisted/during.rs defines the macro during_impl.
• source_assisted/after.rs defines the macro after_impl.

The macros allow for building the same code against different FIDL libraries without repetition.