tests/test-module-imports.t

import-checker: make imported_modules yield absolute dotted_name_of_path

This patch makes `imported_modules()` always yield absolute
`dotted_name_of_path()`-ed name by strict detection with
`fromlocal()`.

This change improves circular detection in some points:

  - locally defined modules, of which name collides against one of
    standard library, can be examined correctly

    For example, circular import related to `commands` is overlooked
    before this patch.

  - names not useful for circular detection are ignored

    Names below are also yielded before this patch:

      - module names of standard library (= not locally defined one)
      - non-module names (e.g. `node.nullid` of `from node import nullid`)

    These redundant names decrease performance of circular detection.

    For example, with files at 1ef96a3b8b89, average loops per file in
    `checkmod()` is reduced from 165 to 109.

  - `__init__` can be handled correctly in `checkmod()`

    For example, current implementation has problems below:

      - `from xxx import yyy` doesn't recognize `xxx.__init__` as imported

      - `xxx.__init__` imported via `import xxx` is treated as `xxx`,
        and circular detection is aborted, because `key` of such
        module name is not `xxx` but `xxx.__init__`

  - it is easy to enhance for `from . import xxx` style or so (in the
    future)

    Module name detection in `imported_modules()` can use information
    in `ast.ImportFrom` fully.

It is assumed that all locally defined modules are correctly specified
to `import-checker.py` at once.

Strictly speaking, when `from foo.bar.baz import module1` imports
`foo.bar.baz.module1` module, current `imported_modules()` yields only
`foo.bar.baz.__init__`, even though also `foo.__init__` and
`foo.bar.__init__` should be yielded to detect circular import
exactly.

But this limitation is reasonable one for improvement in this patch,
because current `__init__` files in Mercurial seems to be implemented
carefully.

#require test-repo

This code uses the ast module, which was new in 2.6, so we'll skip
this test on anything earlier.
  $ $PYTHON -c 'import sys ; assert sys.version_info >= (2, 6)' || exit 80

  $ import_checker="$TESTDIR"/../contrib/import-checker.py

Run the doctests from the import checker, and make sure
it's working correctly.
  $ TERM=dumb
  $ export TERM
  $ python -m doctest $import_checker

  $ cd "$TESTDIR"/..

There are a handful of cases here that require renaming a module so it
doesn't overlap with a stdlib module name. There are also some cycles
here that we should still endeavor to fix, and some cycles will be
hidden by deduplication algorithm in the cycle detector, so fixing
these may expose other cycles.

  $ hg locate 'mercurial/**.py' | sed 's-\\-/-g' | python "$import_checker" -
  mercurial/dispatch.py mixed imports
     stdlib:    commands
     relative:  error, extensions, fancyopts, hg, hook, util
  mercurial/fileset.py mixed imports
     stdlib:    parser
     relative:  error, merge, util
  mercurial/revset.py mixed imports
     stdlib:    parser
     relative:  error, hbisect, phases, util
  mercurial/templater.py mixed imports
     stdlib:    parser
     relative:  config, error, templatefilters, templatekw, util
  mercurial/ui.py mixed imports
     stdlib:    formatter
     relative:  config, error, scmutil, util
  Import cycle: mercurial.cmdutil -> mercurial.context -> mercurial.subrepo -> mercurial.cmdutil
  Import cycle: mercurial.commands -> mercurial.commandserver -> mercurial.dispatch -> mercurial.commands