[lldb] Implement python __repr__ #5351
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
When using the `script` Python repl, SB objects are printed in a way that gives the user no information. The simplest example is: ``` (lldb) script lldb.debugger <lldb.SBDebugger; proxy of <Swig Object of type 'lldb::SBDebugger *' at 0x1097a5de0> > ``` This output comes from the Python repl printing the `repr()` of an object. None of the SB classes implement `__repr__`, and all print like the above. However, many (most?, all?) SB classes implement `__str__`. Because they implement `__str__`, a more detailed output can be had by `print`ing the object, for example: ``` (lldb) script print(lldb.debugger) Debugger (instance: "debugger_1", id: 1) ``` For convenience, this change switches all SB classes that implement to `__str__` to instead implement `__repr__`. **The result is that `str()` and `repr()` will produce the same output**. This is because `str` calls `__repr__` for classes that have no `__str__` method. The benefit being that when writing a `script` invocation, you don't need to remember to wrap in `print()`. If that isn't enough motivation, consider the case where your Python expression results in a list of SB objects, in that case you'd have to `map` or use a list comprehension like `[str(x) for x in <expr>]` in order to see the details of the objects in the list. For reference, the docs for `repr` say: > repr(object) > Return a string containing a printable representation of an object. For > many types, this function makes an attempt to return a string that would > yield an object with the same value when passed to eval(); otherwise, the > representation is a string enclosed in angle brackets that contains the > name of the type of the object together with additional information often > including the name and address of the object. A class can control what this > function returns for its instances by defining a __repr__() method. and the docs for `__repr__` say: > object.__repr__(self) > Called by the repr() built-in function to compute the “official” string > representation of an object. If at all possible, this should look like a > valid Python expression that could be used to recreate an object with the > same value (given an appropriate environment). If this is not possible, a > string of the form <...some useful description...> should be returned. The > return value must be a string object. If a class defines __repr__() but not > __str__(), then __repr__() is also used when an “informal” string > representation of instances of that class is required. > > This is typically used for debugging, so it is important that the > representation is information-rich and unambiguous. Even if it were convenient to construct Python expressions for SB classes so that they could be `eval`'d, however for typical lldb usage, I can't think of a motivating reason to do so. As it stands, the only action the docs say to do, that this change doesn't do, is wrap the `repr` string in `<>` angle brackets. An alternative implementation is to change lldb's python repl to apply `str()` to the top level result. While this would work well in the case of a single SB object, it doesn't work for a list of SB objects, since `str([x])` uses `repr` to convert each list element to a string. Differential Revision: https://reviews.llvm.org/D127458 (cherry picked from commit c7a56af)
|
@swift-ci test |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Cherry pick D127458 (c7a56af) to define
__repr__instead of__str__.Additionally updates the static copy of the bindings.