ioeric added inline comments.
================
Comment at: clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp:353
+ const FileEntry *Entry = FileAndReplacements.first;
+ ReplacementsToAtomicChanges DeduplicatedChanges(SM, Entry);
+ for (const auto &R : FileAndReplacements.second)
----------------
jdemeule wrote:
> ioeric wrote:
> > jdemeule wrote:
> > > ioeric wrote:
> > > > Sorry that I didn't make myself clear... what you had in the previous
> > > > revision was correct (for the current use case of
> > > > apply-all-replacements) i.e. store all replacements in one
> > > > `AtomicChange`, which allows you to detect conflicts on the fly. So the
> > > > code here can be simplified as:
> > > >
> > > > ```
> > > > ...
> > > > Entry = ...;
> > > > AtomicChange FileChange;
> > > > for (const auto &R : FileAndReplacements.second) {
> > > > auto Err = FileChange.replace( <args from R> );
> > > > if (Err)
> > > > reportConflict(Entry, std::move(Err)); // reportConflict as we go
> > > > }
> > > > FileChanges.emplace(Entry, {FileChange});
> > > > ...
> > > > ```
> > > >
> > > > I think with this set up, you wouldn't need
> > > > `ReplacementsToAtomicChanges`, `ConflictError` and `reportConflicts`.
> > > I think I have over-interpreting your previous comment :-)
> > > However, I am still confused about error reporting.
> > > Currently, clang-apply-replacements reports conflicting replacement per
> > > file and per conflict.
> > > For example:
> > > ```
> > > There are conflicting changes to XXX:
> > > The following changes conflict:
> > > Replace 8:8-8:33 with "AAA"
> > > Replace 8:8-8:33 with "BBB"
> > > Remove 8:10-8:15
> > > Insert at 8:14 CCC
> > > ```
> > >
> > > With this patch, conflict are reported by pair (first
> > > replacement/conflicted one) and I am able to print the corresponding file
> > > only once (thanks to the defered reporting).
> > > ```
> > > There are conflicting changes to XXX:
> > > The following changes conflict:
> > > Replace 8:8-8:33 with "AAA"
> > > Replace 8:8-8:33 with "BBB"
> > > The following changes conflict:
> > > Replace 8:8-8:33 with "AAA"
> > > Remove 8:10-8:15
> > > The following changes conflict:
> > > Replace 8:8-8:33 with "AAA"
> > > Insert at 8:14 CCC
> > > ```
> > >
> > > I prefer the way you suggest to report conflict but we will loose or
> > > print conflicting file at each conflict detected.
> > > I even more prefer to use `llvm::toString(std::move(Err))` but this will
> > > fully change the reporting and will also be reported by pair.
> > > ```
> > > The new replacement overlaps with an existing replacement.
> > > New replacement: XXX: 106:+26:"AAA"
> > > Existing replacement: XXX: 106:+26:"BBB"
> > > The new replacement overlaps with an existing replacement.
> > > New replacement: XXX: 106:+26:"AAA"
> > > Existing replacement: XXX: 112:+0:"CCC"
> > > The new replacement overlaps with an existing replacement.
> > > New replacement: XXX: 106:+26:"AAA"
> > > Existing replacement: XXX: 108:+12:""
> > > ```
> > I am inclined to changing the current behavior and reporting by pairs
> > because
> > 1) this would simplify the code a lot.because we could basically reuse the
> > conflict detection from replacement library.
> > 2) IMO, pairs are easier to read than grouping multiple conflicts - users
> > would still need to interpret the conflicts and figure out how all
> > replacements conflict in a group, while reporting as pairs already gives
> > you this information.
> > 3) in practice, it's uncommon to see more than two conflicting replacements
> > at the same code location.
> >
> > I would vote for the last approach (with `llvm::toString(std::move(Err))`)
> > which is easy to implement and doesn't really regress the `UI` that much.
> > WDYT?
> I think if we can use `llvm::toString(std::move(Err))` for this patch, it
> will simplify the code and reuse already existing error message. Even if I
> found file+offset conflict location less readable than file+line+column.
>
> I have made some prototype to "enhance" error reporting but I think they
> should be put in dedicated patches and need further discutions.
> During my "research" I found we can use:
> * Conflict marker format.
> ```
> /src/basic.h
> @@ 12:23-12:23 @@
> <<<<<<< Existing replacement
> virtual void func() noexcept {}
> =======
> virtual void func() override {}
> >>>>>>> New replacement
> ```
> * A unified diff like.
> ```
> /src/basic.h
> @@ 12:23-12:23 @@
> - virtual void func() {}
> + virtual void func() noexcept {}
> + virtual void func() override {}
> ```
> * A clang like diagnostic message.
> ```
> /src/basic.h
> @@ 12:23-12:23 @@
> virtual void func() {}
> ^
> noexcept
> virtual void func() {}
> ^
> override
> ```
>
The conflict marker format looks promising!
You are right regarding offset vs line+column location. I agree offset is less
readable. I think we could probably build offset -> line+column translation
into `ReplacementError` if necessary. For example, we could add a pretty-print
method/helper that takes in source code and outputs readable error messages
with offset translated to line+columns according to the source code, which is
basically what the current `replaceConflict` function does. Ideally, that would
also handle/consume the underlying errors so that we could switch to use that
instead of `llvm::toString`.
https://reviews.llvm.org/D43764
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