[9.3.0] Don't crash on a constraint value repeated via an alias (https://github.com/bazelbuild/bazel/pull/30488) - #30534
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…0488) ### Description `ConstraintCollection.validateConstraints` explicitly permits multiple instances of the *same* constraint value and only rejects different values for the same constraint setting. `ConstraintCollection.Builder#build` then collected the values into an `ImmutableMap` keyed by constraint setting without a merge function, so any repetition crashed Bazel with Multiple entries with same key: ConstraintSettingInfo(...)=ConstraintValueInfo(...) This is easy to hit accidentally when a constraint value is referenced both directly and through an `alias`, e.g. `@bazel_tools//tools/cpp:mingw` and `@rules_cc//cc/private/toolchain:mingw` in a `toolchain`'s `target_compatible_with`. Since validation guarantees that all values for a given setting are equal at this point, keep the first one. ### Motivation Fixes bazel-contrib/rules_go#4665 ### Build API Changes No ### Checklist - [x] I have added tests for the new use cases (if any). - [x] I have updated the documentation (if applicable). ### Release Notes RELNOTES: None Closes bazelbuild#30488. PiperOrigin-RevId: 956129840 Change-Id: Ic5771803e104d1e3550527a11e6403dcb3cfe535
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Description
ConstraintCollection.validateConstraintsexplicitly permits multiple instances of the same constraint value and only rejects different values for the same constraint setting.ConstraintCollection.Builder#buildthen collected the values into anImmutableMapkeyed by constraint setting without a merge function, so any repetition crashed Bazel withThis is easy to hit accidentally when a constraint value is referenced both directly and through an
alias, e.g.@bazel_tools//tools/cpp:mingwand@rules_cc//cc/private/toolchain:mingwin atoolchain'starget_compatible_with.Since validation guarantees that all values for a given setting are equal at this point, keep the first one.
Motivation
Fixes bazel-contrib/rules_go#4665
Build API Changes
No
Checklist
Release Notes
RELNOTES: None
Closes #30488.
PiperOrigin-RevId: 956129840
Change-Id: Ic5771803e104d1e3550527a11e6403dcb3cfe535
Commit afd06ce