[PATCH] D43764: [clang-apply-replacements] Convert tooling::Replacements to tooling::AtomicChange for conflict resolving of changes, code cleanup, and code formatting.

[Eric Liu via Phabricator via cfe-commits]

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:
> > 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?


https://reviews.llvm.org/D43764