[PATCH] D114225: Add JSONScopedPrinter to llvm-readelf

[Jayson Yan via Phabricator via llvm-commits]

Jaysonyan added inline comments.


================
Comment at: llvm/tools/llvm-readobj/llvm-readobj.cpp:340
 
-  if (opts::Output == opts::LLVM || opts::InputFilenames.size() > 1 || A) {
-    Writer.startLine() << "\n";
-    Writer.printString("File", FileStr);
-  }
-  if (opts::Output == opts::LLVM) {
-    Writer.printString("Format", Obj.getFileFormatName());
-    Writer.printString("Arch", Triple::getArchTypeName(Obj.getArch()));
-    Writer.printString(
-        "AddressSize",
-        std::string(formatv("{0}bit", 8 * Obj.getBytesInAddress())));
-    Dumper->printLoadName();
-  }
+  Dumper->printFileSummary(FileStr, Obj, opts::InputFilenames, A);
 
----------------
jhenderson wrote:
> I guess there's a subtle behaviour change as a result of this patch, which wouldn't hurt to be called out in the commit description, but I otherwise think is fine: if a user had exactly one non-ELF object/archive (e.g. a COFF object), and they had previously specified `--elf-output-style=GNU` (or run using llvm-readelf, which has that as the default), they would previously have had no file summary, but now they'd get the default summary, provided by the ObjDumper class. Similarly, if they'd had more than one input, or the objects were in an archive, they'd before have had just the `File` part of the summary, but now they have the full file summary.
I placed the same `opts::InputFilenames.size() > 1 || A` check inside `GNUELFDumper::printFileSummary` method so I think the behaviour is the same.

Before, if the `opts::Output` is `LLVM` both `if(...)` statements would trigger. Now the `ObjDumper::printFileSummary` performs all the work in both if statements and would be called for any `Dumper` that is not `GNUELFDumper` or `JSONELFDumper` which should be any case where `opts::Output` is `LLVM`.

And the `GNUELFDumper::printFileSummary` only prints the `File` part and still does the multiple inputs / archive check. 


================
Comment at: llvm/tools/llvm-readobj/llvm-readobj.cpp:613-615
+  std::unique_ptr<ListScope> D;
+  if (opts::Output == opts::JSON)
+    D = std::make_unique<ListScope>(*Writer.get());
----------------
jhenderson wrote:
> To recap: we only need this scope for JSON, so that there is a top-level object, ensuring we always have valid JSON in the output. What's stopping us making the ListScope a member of the `JSONScopedPrinter` class, so that the scoping is added on construction/destruction of the Writer?
> 
> Taking it from another point of view, if you had another piece of client code using `JSONScopedPrinter`, would they expect the output to be a valid JSON object, without additional changes, or expect to need to provide the outer object wrapping themselves? If the former, the scoping belongs to the `JSCONScopedPrinter`.
I think providing an optional `ListScope`/`DictScope` constructor could be a nice quality-of-life improvement, but I think there should still be a way to construct a `JSONScopedPrinter` without `{}`/`[]` already added. Since technically, `"string"` is still valid json so I wouldn't want to remove the option to output json that don't have an outermost `[]`/`{}`.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D114225/new/

https://reviews.llvm.org/D114225