NuGet dependency solver doesn't correctly handle a minimum version that doesn't exist.

[brettfo]

Consider the following packages:

Top.Level.Package

• depends on Transitive.Package version >= 1.0.0

Transitive.Package

• versions 1.0.1 and 1.0.2 exist

When asked to update Transitive.Package from 1.0.1 to 1.0.2, ideally only Top.Level.Package would be updated, but its minimum dependent package version is >= 1.0.0, but that package doesn't exist; instead, 1.0.1 would be resolved.

This causes problems in the dependency solver because at certain points Transitive.Package is explicitly set to its minimum version of 1.0.0 to attempt an update, but since that doesn't exist, the packages can't be solved.

The likely solution is to set the minimum version of Transitive.Package to the smallest available version that satisfies the requirements; something like minVersion = allVersions.Where(v => v >= minVersion).First() so that all future calls to set the minimum version arrive at one that specifically exists.

Consider the unit test modified in PR #11151 as a good test scenario. (N.b. The transitive dependency of Buildalyzer Microsoft.CodeAnalysis.* 4.0.0 doesn't exist, but 4.0.1 does.)