(Deleted my comment since I realized that it can be both an empty set and None.)

Seems like this breaks several other things.

I'm not sure which fix is better, or if there is any other superior solution available. Based on the commit history, there are two potential fixes:

1. alternative fix. The fix produces theexpected outcomeand aligns with the description in thedoc:

If labelOnlyBase is False, these two numbers control the labeling of ticks that are not at integer powers of base; normally these are the minor ticks. The controlling parameter is the log of the axis data range. In the typical case where base is 10 it is the number of decades spanned by the axis, so we can call it 'numdec'. If numdec <= all, all minor ticks will be labeled. If all < numdec <= subset, then only a subset of minor ticks will be labeled, so as to avoid crowding. If numdec > subset then no minor ticks will be labeled.
...
To disable labeling of minor ticks when 'labelOnlyBase' is False, use minor_thresholds=(0, 0). This is the default for the "classic" style.

Note that it assumeslabelOnlyBase isTrue for all the major formatters whileFalse for minor formatters, which could contradict with thedoc stating:

This is normally True for major ticks and False for minor ticks.

What about "abnormally"? Can a major formatter have 'labelOnlyBase' set toFalse? Is there an exceptional case?

2. FIX: LogFormatter minor ticks with minor_thresholds of (0,0) misbehaves. It uses the same minor_thresholds logic for both major and minor formatter, and allows a major formatter withlabelOnlyBase=False or a minor formatter withlabelOnlyBase=True. But it contradicts with the following description in the documentation:

If labelOnlyBase is False, these two numbers control the labeling of ticks that are not at integer powers of base; normally these are the minor ticks. The controlling parameter is the log of the axis data range. In the typical case where base is 10 it is the number of decades spanned by the axis, so we can call it 'numdec'. If numdec <= all, all minor ticks will be labeled. If all < numdec <= subset, then only a subset of minor ticks will be labeled, so as to avoid crowding. If numdec > subset then no minor ticks will be labeled.

Whenminor_thresholds is set to(0, 0), namely,numdec > subset, a formatter labels bases only whetherlabelOnlyBase is True or not. In the example from issue#25896, its outcome is as follows:

importmatplotlib.pyplotaspltimportmatplotlib.tickerasmtickerfig,ax=plt.subplots()ax.set_yscale("log")formatter=mticker.LogFormatter(minor_thresholds=(0,0))ax.yaxis.set_minor_formatter(formatter)ax.set_ylim(10,20)formatter(10)# '10'formatter(11)# ''formatter(12)# ''formatter(13)# ''formatter(14)# ''formatter(15)# ''formatter(16)# ''

Furthermore, what does the term "classic" style refer to in the documentation? Maybe we could provide a more precise description.

Classic is the pre-2.0 default style.

Hi@oscargus, could you review the PR again?