Various fixes to lazy imports

[jdemeyer]

Assorted fixes to lazy imports:

1. Drop support for lazy_import(overwrite=False) which was used only in one place in a dubious way to implement a 2-level lazy import (a lazy import being lazily imported).

2. More optimal code for binary operations like __add__ by avoiding the operator module.

3. Move the code to replace a lazy import in a class namespace from _get_object() to __get__.

4. Partially inline _get_object() with a new cdef inline function for the case that the object has been initialized.

5. A lazy import without at_startup being imported at startup is now an error (it used to just print a message, which is less useful than an error traceback).

6. Implement ​__matmul__ (pointless in Python 2, but useful for Python 3).

7. Clean up the function lazy_import a bit.

[jdemeyer]

New commits:

​94302ca	Do not declare functions/methods as "cdef inline"
​9e5715e	Various improvements to lazy imports
​d2bb491	Whitespace fix

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​8aac18a

Various improvements to lazy imports

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​f3ede00

Use exact type check in obj()

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​7bf2ce8

Partially inline LazyImport._get_object()

[vdelecroix]

You expect the following traceback to be accepted by doctests?

Traceback (most recent call last):
  File "/usr/local/src/sage-config/local/lib/python2.7/site-packages/sage/doctest/forker.py", line 498, in _run
    self.compile_and_execute(example, compiler, test.globs)
  File "/usr/local/src/sage-config/local/lib/python2.7/site-packages/sage/doctest/forker.py", line 861, in compile_and_execute
    exec(compiled, globs)
  File "<doctest sage.misc.lazy_import.test_fake_startup[3]>", line 1, in <module>
    my_ZZ(Integer(123))
  File "sage/misc/lazy_import.pyx", line 346, in sage.misc.lazy_import.LazyImport.__call__ (build/cythonized/sage/misc/lazy_import.c:3495)
    return self._get_object()(*args, **kwds)
  File "sage/misc/lazy_import.pyx", line 210, in sage.misc.lazy_import.LazyImport._get_object (build/cythonized/sage/misc/lazy_import.c:2139)
    raise RuntimeError(f"resolving lazy import {self._name} during startup")
RuntimeError: resolving lazy import ZZ during startup

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​4dda1ae

Fix traceback

[jdemeyer]

Replying to vdelecroix:

You expect the following traceback to be accepted by doctests?

Apparently yes (see patchbot) :-)

Anyway, I fixed it.

[vdelecroix]

Weird patchbot failure on quasar! Do you think it is related to your ticket?

[jdemeyer]

Replying to vdelecroix:

Weird patchbot failure on quasar! Do you think it is related to your ticket?

Almost certainly not.

[vdelecroix]

Replying to jdemeyer:

Replying to vdelecroix:

Weird patchbot failure on quasar! Do you think it is related to your ticket?

Almost certainly not.

Note that all tests pass on some other tickets. I will relaunch it.

[jdemeyer]

The most recent patchbot run passes all tests.

[vdelecroix]

The documentation of the overwrite argument in lazy_import disappeard.

NOTE: though it is deprecated

[vdelecroix]

Why stuff from sage.dynamics.interval_exchanges and sage.dynamics.flat_surfaces not lazily imported anymore?

[jdemeyer]

As I tried to explain in the ticket description, it was lazily importing a lazy import.

[jdemeyer]

Ping?

[vdelecroix]

done!