Monorepo?

[Walter Bright]

On 2/6/2023 8:48 AM, Mathias LANG wrote:
> On Monday, 6 February 2023 at 10:22:32 UTC, Atila Neves wrote:
>> Now that dmd/druntime is in one repo, is there a good reason to not include 
>> Phobos?
> 
> Because it will inevitably lead to circular dependencies, something Walter is 
> already complaining about.

More specifically, I complained about the order in which things were built and 
tested.

There is a test suite designed to test the compiler. There are many hundreds of 
these tests. Each is standalone, only a few lines long. I.e. they are already 
reduced and isolated. (The source of most of these were bugs that were fixed.) 
When something in that test suite fails, one can usually go directly to the problem.

But what happens with the way the test suite is run is:

1. the compiler gets built

2. then the compiler is used to compile druntime. Boom, the compiler crashes. 
Now you've got hours of work to reduce the problem.

3. or the compiler is used to build checkwhitespace. Boom, the compiler crashes, 
or checkwhitespace crashes. Hours of work ahead.

4. or the compiler is used to bootstrap itself. Boom, it creates a compiler that 
crashes, or the created compiler compiles code badly. Hours of work ahead.

5. or the compiler is used to build build.d. build itself then crashes. Hours of 
work ahead.

6. or the compiler is used to build Phobos. It crashes building Phobos, or the 
Phobos unittests fail. Hours of work ahead.

--- OR ---

the freshly built compiler is used to run the compiler test suite. test1234.d 
fails. A few minutes of work identifying what went wrong, because you've only 
got 6 lines of code to look at rather than 100,000 lines.

2,3,4,5,6 have all routinely happened.

At least (mostly) the compiler test suite does not depend on a functioning 
Phobos. Myself (and others) have removed nearly all of those dependencies.

Another advantage of running the compiler test suite first is it is relatively 
small and runs fast. Hence, you get quick turnaround.