Support two-step method calls and allow retrieving built-in methods using getattr #8931
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using getattr. It's now possible to call methods in two steps `y = x.f; y()`
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Assigning to @vladmos for review and import fyi @alandonovan, this fixes a very long-standing issue |
bazel-io
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Dec 2, 2019
github.com//pull/8931 was an incomplete fix to b/21392896: it allowed 'x.f()' to be expressed as 'y=x.f; y()' in most cases, but not all. In particular, it did not address the to_json and to_proto methods of structs (which we should get rid of, BTW). This change is an ad-hoc fix for those two methods. A more principled fix will have to wait till an integrated clean-up of Info/StructImpl/NativeInfo. This change is a prerequisite for fixing github.com//issues/10339, which is in turn a prerequisite for various simplifications and optimizations to Starlark's function calling mechanism. I audited Google's .bzl corpus for cases where the three-argument getattr(x, name, dflt) was called with either an arbitrary name or a name obtained from dir(x) without filtering, and where subsequent operations might change their behavior if given a bound method instead of 'dflt'. This turned up only two locations, both easily fixed (CL 283224061). PiperOrigin-RevId: 283433923
luca-digrazia
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Sep 4, 2022
github.com/bazelbuild/bazel/pull/8931 was an incomplete fix to b/21392896: it allowed 'x.f()' to be expressed as 'y=x.f; y()' in most cases, but not all. In particular, it did not address the to_json and to_proto methods of structs (which we should get rid of, BTW). This change is an ad-hoc fix for those two methods. A more principled fix will have to wait till an integrated clean-up of Info/StructImpl/NativeInfo. This change is a prerequisite for fixing github.com/bazelbuild/bazel/issues/10339, which is in turn a prerequisite for various simplifications and optimizations to Starlark's function calling mechanism. I audited Google's .bzl corpus for cases where the three-argument getattr(x, name, dflt) was called with either an arbitrary name or a name obtained from dir(x) without filtering, and where subsequent operations might change their behavior if given a bound method instead of 'dflt'. This turned up only two locations, both easily fixed (CL 283224061). PiperOrigin-RevId: 283433923
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Related: bazelbuild/starlark#20 (comment), #5224
It's now possible to call methods in two steps
y = x.f; y()Also,
getattrcan now be used to retrieve built-in methods.