[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:
> > 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