OSX needs to treated as the same platform as MacOS, everywhere

[buyaa-n]

OSX needs to treated as the same platform as MacOS, everywhere

Somehow the code handling this logic lost 🙅 (i remember had it handled in my first version, I guess it is lost in the design change refactoring result).

The brute force way for treating OSX as MacOS would add additional check for each OS platform check and platform lookup, which don't like to do. So instead:

• Whenever an OSPlatform attribute with OSX found for an API adding it as MacOs in the internal cache, so no need to add OSX specific special handling anymore
• The only issue with this solution can be seen in reporting the incompatible APIs, i.e. when there is OSX specific API used from an incompatible call site then developers would get a warning that the API is supported on MacOS instead of OSX. Handling this issue with reporting the platform as MacOS/OSX - meaning it can be MacOS or OSX

Example:

class Test
{
    public void Api_Usage()
    {
        if (OperatingSystem.IsWindows() ||
            OperatingSystem.IsLinux() ||
            OperatingSystem.IsMacOS())
        {
            Api();
            Api2(); // All supported platforms guarded
        }

        [|Api()|]; // This call site is reachable on all platforms. 'Test.Api()' is only supported on: 'MacOS/OSX', 'Linux', 'windows'.
        [|Api2()|]; // This call site is reachable on all platforms. 'Test.Api2()' is only supported on: 'MacOS/OSX', 'Linux', 'windows'.
    }

    [SupportedOSPlatform("macos")]
    [SupportedOSPlatform("windows")]
    [SupportedOSPlatform("Linux")]
    void Api() { }

    [SupportedOSPlatform("windows")]
    [SupportedOSPlatform("Osx")]
    [SupportedOSPlatform("Linux")]
    void Api2() { }
}

[codecov]

Codecov Report

Merging #5012 (e91175a) into release/6.0.1xx-preview4 (1dcfb32) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@                     Coverage Diff                      @@
##           release/6.0.1xx-preview4    #5012      +/-   ##
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- Coverage                     95.57%   95.54%   -0.04%     
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  Files                          1177     1188      +11     
  Lines                        269979   273151    +3172     
  Branches                      16362    16537     +175     
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+ Hits                         258038   260984    +2946     
- Misses                         9810     9976     +166     
- Partials                       2131     2191      +60