view tests/test-diff-binary-file.t @ 29375:fcaf20175b1b

demandimport: delay loading for "from a import b" with absolute_import

Before this patch, "from a import b" doesn't delay loading module "b",
if absolute_import is enabled, even though "from . import b" does.

For example:

  - it is assumed that extension X has "from P import M" for module M
    under package P with absolute_import feature

  - if importing module M is already delayed before loading extension
    X, loading module M in extension X is delayed until actually
    referring

    util, cmdutil, scmutil or so of Mercurial itself should be
    imported by "from . import M" style before loading extension X

  - otherwise, module M is loaded immediately at loading extension X,
    even if extension X itself isn't used at that "hg" command invocation

    Some minor modules (e.g. filemerge or so) of Mercurial itself
    aren't imported by "from . import M" style before loading
    extension X. And of course, external libraries aren't, too.

This might cause startup performance problem of hg command, because
many bundled extensions already enable absolute_import feature.

To delay loading module for "from a import b" with absolute_import
feature, this patch does below in "from a (or .a) import b" with
absolute_import case:

  1. import root module of "name" by system built-in __import__
     (referred as _origimport)

  2. recurse down the module chain for hierarchical "name"

     This logic can be shared with non absolute_import
     case. Therefore, this patch also centralizes it into chainmodules().

  3. and fall through to process elements in "fromlist" for the leaf
     module of "name"

     Processing elements in "fromlist" is executed in the code path
     after "if _pypy: .... else: ..." clause. Therefore, this patch
     replaces "if _pypy:" with "elif _pypy:" to share it.

At 4f1144c3c72b introducing original "work around" for "from a import
b" case, elements in "fromlist" were imported with "level=level". But
"level" might be grater than 1 (e.g. level=2 in "from .. import b"
case) at demandimport() invocation, and importing direct sub-module in
"fromlist" with level grater than 1 causes unexpected result.

IMHO, this seems main reason of "errors for unknown reason" described
in 4f1144c3c72b, and we don't have to worry about it, because this
issue was already fixed by 78d05778907b.

This is reason why this patch removes "errors for unknown reasons"
comment.

  $ hg init a
  $ cd a
  $ cp "$TESTDIR/binfile.bin" .
  $ hg add binfile.bin
  $ hg ci -m 'add binfile.bin'

  $ echo >> binfile.bin
  $ hg ci -m 'change binfile.bin'

  $ hg revert -r 0 binfile.bin
  $ hg ci -m 'revert binfile.bin'
  $ hg cp binfile.bin nonbinfile
  $ echo text > nonbinfile
  $ hg ci -m 'make non-binary copy of binary file'

  $ hg diff --nodates -r 0 -r 1
  diff -r 48b371597640 -r acea2ab458c8 binfile.bin
  Binary file binfile.bin has changed

  $ hg diff --nodates -r 0 -r 2

  $ hg diff --git -r 0 -r 1
  diff --git a/binfile.bin b/binfile.bin
  index 37ba3d1c6f17137d9c5f5776fa040caf5fe73ff9..58dc31a9e2f40f74ff3b45903f7d620b8e5b7356
  GIT binary patch
  literal 594
  zc$@)J0<HatP)<h;3K|Lk000e1NJLTq000mG000mO0ssI2kdbIM00009a7bBm000XU
  z000XU0RWnu7ytkO2XskIMF-Uh9TW;VpMjwv0005-Nkl<ZD9@FWPs=e;7{<>W$NUkd
  zX$nnYLt$-$V!?uy+1V%`z&Eh=ah|duER<4|QWhju3gb^nF*8iYobxWG-qqXl=2~5M
  z*IoDB)sG^CfNuoBmqLTVU^<;@nwHP!1wrWd`{(mHo6VNXWtyh{alzqmsH*yYzpvLT
  zLdY<T=ks|woh-`&01!ej#(xbV1f|pI*=%;d-%F*E*X#ZH`4I%6SS+$EJDE&ct=8po
  ziN#{?_j|kD%Cd|oiqds`xm@;oJ-^?NG3Gdqrs?5u*zI;{nogxsx~^|Fn^Y?Gdc6<;
  zfMJ+iF1J`LMx&A2?dEwNW8ClebzPTbIh{@$hS6*`kH@1d%Lo7fA#}N1)oN7`gm$~V
  z+wDx#)OFqMcE{s!JN0-xhG8ItAjVkJwEcb`3WWlJfU2r?;Pd%dmR+q@mSri5q9_W-
  zaR2~ECX?B2w+zELozC0s*6Z~|QG^f{3I#<`?)Q7U-JZ|q5W;9Q8i_=pBuSzunx=U;
  z9C)5jBoYw9^?EHyQl(M}1OlQcCX>lXB*ODN003Z&P17_@)3Pi=i0wb04<W?v-u}7K
  zXmmQA+wDgE!qR9o8jr`%=ab_&uh(l?R=r;Tjiqon91I2-hIu?57~@*4h7h9uORK#=
  gQItJW-{SoTm)8|5##k|m00000NkvXXu0mjf3JwksH2?qr
  

  $ hg diff --git -r 0 -r 2

  $ hg diff --config diff.nobinary=True --git -r 0 -r 1
  diff --git a/binfile.bin b/binfile.bin
  Binary file binfile.bin has changed

  $ HGPLAIN=1 hg diff --config diff.nobinary=True --git -r 0 -r 1
  diff --git a/binfile.bin b/binfile.bin
  index 37ba3d1c6f17137d9c5f5776fa040caf5fe73ff9..58dc31a9e2f40f74ff3b45903f7d620b8e5b7356
  GIT binary patch
  literal 594
  zc$@)J0<HatP)<h;3K|Lk000e1NJLTq000mG000mO0ssI2kdbIM00009a7bBm000XU
  z000XU0RWnu7ytkO2XskIMF-Uh9TW;VpMjwv0005-Nkl<ZD9@FWPs=e;7{<>W$NUkd
  zX$nnYLt$-$V!?uy+1V%`z&Eh=ah|duER<4|QWhju3gb^nF*8iYobxWG-qqXl=2~5M
  z*IoDB)sG^CfNuoBmqLTVU^<;@nwHP!1wrWd`{(mHo6VNXWtyh{alzqmsH*yYzpvLT
  zLdY<T=ks|woh-`&01!ej#(xbV1f|pI*=%;d-%F*E*X#ZH`4I%6SS+$EJDE&ct=8po
  ziN#{?_j|kD%Cd|oiqds`xm@;oJ-^?NG3Gdqrs?5u*zI;{nogxsx~^|Fn^Y?Gdc6<;
  zfMJ+iF1J`LMx&A2?dEwNW8ClebzPTbIh{@$hS6*`kH@1d%Lo7fA#}N1)oN7`gm$~V
  z+wDx#)OFqMcE{s!JN0-xhG8ItAjVkJwEcb`3WWlJfU2r?;Pd%dmR+q@mSri5q9_W-
  zaR2~ECX?B2w+zELozC0s*6Z~|QG^f{3I#<`?)Q7U-JZ|q5W;9Q8i_=pBuSzunx=U;
  z9C)5jBoYw9^?EHyQl(M}1OlQcCX>lXB*ODN003Z&P17_@)3Pi=i0wb04<W?v-u}7K
  zXmmQA+wDgE!qR9o8jr`%=ab_&uh(l?R=r;Tjiqon91I2-hIu?57~@*4h7h9uORK#=
  gQItJW-{SoTm)8|5##k|m00000NkvXXu0mjf3JwksH2?qr
  


  $ hg diff --git -r 2 -r 3
  diff --git a/binfile.bin b/nonbinfile
  copy from binfile.bin
  copy to nonbinfile
  index 37ba3d1c6f17137d9c5f5776fa040caf5fe73ff9..8e27be7d6154a1f68ea9160ef0e18691d20560dc
  GIT binary patch
  literal 5
  Mc$_OqttjCF00uV!&;S4c
  

  $ cd ..