[Paginator] numberOfPages is off by one

[haochi]

Bug, feature request, or proposal:

Bug: numberOfPages is off by one.

Right now numberOfPages() is calculated as

Math.ceil(this.length / this.pageSize) - 1;

Which would work nicely for zero-based calculations, but doesn't work so well for actual display or the mental model of what "number of pages" represent.

For example:

• length=1, pageSize=5 => numberOfPages() returns 0 (there should be 1 page right?)

Consider the example of splitting an array into page chunks (i.e. any[] => any[][]), the resulting array be size of 1.

What is the expected behavior?

Should return the current page count.

What is the current behavior?

As described above.

What is the use-case or motivation for changing an existing behavior?

See above.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

since v5.2.0, also in the v6.0.0-rc.0

Is there anything else we should know?

There doesn't seem to be any tests for numberOfPages, a public method.

[andrewseguin]

Huh...that does seem confusing. I'm surprised it is a public method since it really should be named something like getMaxPageIndex which would be internal only.

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