dexonsmith added inline comments.

================
Comment at: clang/test/ClangScanDeps/modules-inferred-explicit-build.m:13-17
+// RUN: %clang @%t.inferred.rsp -pedantic -Werror
+// RUN: %clang @%t.system.rsp -pedantic -Werror
+// RUN: %clang -x objective-c -fsyntax-only %t.dir/modules_cdb_input.cpp \
+// RUN:   -F%S/Inputs/frameworks -fmodules -fimplicit-module-maps \
+// RUN:   -pedantic -Werror @%t.tu.rsp
----------------
dexonsmith wrote:
> jansvoboda11 wrote:
> > dexonsmith wrote:
> > > jansvoboda11 wrote:
> > > > dexonsmith wrote:
> > > > > I feel like the clang invocations that build/use modules should be in 
> > > > > `clang/test/Modules`. Two independent things:
> > > > > - Can clang build inferred modules explicitly? (tested in 
> > > > > clang/test/Modules)
> > > > > - Can clang-scan-deps generate deps for inferred modules? (tested in 
> > > > > clang/test/ClangScanDeps)
> > > > I agree that we should test explicit build of inferred modules in 
> > > > `clang/test/Modules` (without `clang-scan-deps`). I'll look into it.
> > > > 
> > > > I'm not sure I'd be happy with only checking the dependencies produced 
> > > > by `clang-scan-deps` here. Testing that the generated command-line 
> > > > actually works is as important IMO, and it will be even more so when we 
> > > > start optimizing the command line (stripping out unused header search 
> > > > paths, definitions etc.).
> > > I'm not sure precisely what you mean by "works". I'm not sure just 
> > > checking if it still compiles tells us much. What's important is that the 
> > > modified options have the same semantics, and I think a subtle change 
> > > that still compiles is more likely than preventing compilation entirely.
> > > 
> > > I don't think it would scale to check for semantic problems here -- that 
> > > needs a body of testcases that covers all the things modules support.
> > > 
> > > One option would be to use the testcases (or a selection of them) in 
> > > clang/test/Modules, by adding an extra RUN line that builds 
> > > clang-scan-deps-discovered modules both with and without command-line 
> > > stripping. For most changes, we can arrange the AST block such that 
> > > skipped options won't affect it, and we could compare the hash of just 
> > > that block. If and when we start stripping ignored `-D` options we'll 
> > > need something smarter, but we can solve that problem later. (Ideally, 
> > > this would just be a mode in clang, `clang -Xclang -fmodules-depscan`, 
> > > which does an initial depscan and builds the modules in order. This might 
> > > actually be an improvement on the existing implicit modules.)
> > > 
> > > @Bigcheese, maybe you can weigh in? If you both think `clang -cc1` should 
> > > be tested here, I'm open to it. (In that case, though, this should not be 
> > > invoking `%clang`, but `%clang_cc1`, I think... or does the response file 
> > > create a driver command-line?)
> > > I'm not sure precisely what you mean by "works". I'm not sure just 
> > > checking if it still compiles tells us much. What's important is that the 
> > > modified options have the same semantics, and I think a subtle change 
> > > that still compiles is more likely than preventing compilation entirely.
> > 
> > I see, that's a good point.
> > 
> > > One option would be to use the testcases (or a selection of them) in 
> > > clang/test/Modules, by adding an extra RUN line that builds 
> > > clang-scan-deps-discovered modules both with and without command-line 
> > > stripping. For most changes, we can arrange the AST block such that 
> > > skipped options won't affect it, and we could compare the hash of just 
> > > that block. If and when we start stripping ignored `-D` options we'll 
> > > need something smarter, but we can solve that problem later. 
> > 
> > Using tests from `clang/test/Modules` sounds nice. What are your concerns 
> > regarding stripping `-D` options?
> > 
> > > In that case, though, this should not be invoking `%clang`, but 
> > > `%clang_cc1`, I think... or does the response file create a driver 
> > > command-line?
> > 
> > The `Tooling/DependencyScanning` library already prepends the `"-cc1"` 
> > argument so that build tools using the API don't have to do that on their 
> > own.
> > 
> > Using tests from clang/test/Modules sounds nice. What are your concerns 
> > regarding stripping -D options?
> 
> Oh, it’s a bit mundane, but that’ll affect the identifier info, which will in 
> turn change the AST block and its hash. I think?
> 
> For a truly explicit module, removing “unused” `-D` options from the 
> identifier table might not be correct, since for semantics you might want 
> importers to pick up those definitions (I think? Are they considered 
> exported?). For implicitly-discovered modules, we know all transitive 
> importers have a superset of `-D`s on their command-lines so it’s safe. 
> 
> Maybe what we can do at the time is turn on a flag to avoid writing unused 
> `-D`s to the serialized identifier table so the hashes will match? Anyway, 
> I’m sure there is a solution. 
> > In that case, though, this should not be invoking %clang, but %clang_cc1, I 
> > think... or does the response file create a driver command-line?
> The Tooling/DependencyScanning library already prepends the "-cc1" argument 
> so that build tools using the API don't have to do that on their own.

I suggest adding a `.cc1` extension to the response files to make that clear to 
anyone reading the test. Maybe `t.inferred.cc1.rsp`.

The third clang invocation doesn't have the response file as the first 
argument, though, so I imagine that one doesn't contain a `-cc1`? (Or if it 
did, I'm not sure how it would work... I'm guessing it only adds arguments that 
happen to match between `-cc1` and driver?)


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D100934/new/

https://reviews.llvm.org/D100934

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