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digitalmars.D.learn - std.path.buildPath

reply Russel Winder via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> writes:
=46rom the manual page on std.path.buildPath:

    writeln(buildPath("foo", "bar", "baz")); // "foo/bar/baz"
    writeln(buildPath("/foo/", "bar/baz")); // "/foo/bar/baz"
    writeln(buildPath("/foo", "/bar")); // "/bar"

I have no idea what drugs the person who chose that last one to be
correct semantics was on at the time, but it was some seriously bad
stuff.

"If any of the path segments are absolute (as defined by isAbsolute),
the preceding segments will be dropped."

I cannot find any excuse for this to be even remotely reasonable.

--=20
Russel.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
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=3D=3D
Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.winder ekiga.n=
et
41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel winder.org.uk
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder
Jun 03 2017
next sibling parent Jacob Carlborg <doob me.com> writes:
On 2017-06-03 16:12, Russel Winder via Digitalmars-d-learn wrote:

 From the manual page on std.path.buildPath:

     writeln(buildPath("foo", "bar", "baz")); // "foo/bar/baz"
     writeln(buildPath("/foo/", "bar/baz")); // "/foo/bar/baz"
     writeln(buildPath("/foo", "/bar")); // "/bar"

 I have no idea what drugs the person who chose that last one to be
 correct semantics was on at the time, but it was some seriously bad
 stuff.

 "If any of the path segments are absolute (as defined by isAbsolute),
 the preceding segments will be dropped."

 I cannot find any excuse for this to be even remotely reasonable.


Unfortunately it's been like this since forever. I mean, I checked the 
git history, it's been like this for as long as we have history, 
including when it was called "join".

-- 
/Jacob Carlborg
Jun 03 2017
prev sibling next sibling parent David Nadlinger <code klickverbot.at> writes:
On Saturday, 3 June 2017 at 14:12:03 UTC, Russel Winder wrote:

 I have no idea what drugs the person who chose that last one to 
 be correct semantics was on at the time, but it was some 
 seriously bad stuff.


Of all people, I certainly didn't expect you to stray so far from 
the tone appropriate here. Please keep it civil.


 I cannot find any excuse for this to be even remotely 
 reasonable.


I suspect the original author had applications in mind where you 
want to resolve user-specified file system paths that might be 
relative or absolute. One could just use buildPath to prepend the 
root path if necessary. (Whether this is useful or just 
unnecessarily error-prone is another question, of course.)

  — David
Jun 03 2017
prev sibling parent reply Jesse Phillips <Jesse.K.Phillips+D gmail.com> writes:
On Saturday, 3 June 2017 at 14:12:03 UTC, Russel Winder wrote:

 From the manual page on std.path.buildPath:

     writeln(buildPath("foo", "bar", "baz")); // "foo/bar/baz"
     writeln(buildPath("/foo/", "bar/baz")); // "/foo/bar/baz"
     writeln(buildPath("/foo", "/bar")); // "/bar"

 I have no idea what drugs the person who chose that last one to 
 be correct semantics was on at the time, but it was some 
 seriously bad stuff.

 "If any of the path segments are absolute (as defined by 
 isAbsolute), the preceding segments will be dropped."

 I cannot find any excuse for this to be even remotely 
 reasonable.


What is your expected behavior? Throw an exception? You can't 
really append an absolute path to another.
Jun 03 2017
parent reply Jacob Carlborg <doob me.com> writes:
On 2017-06-04 07:44, Jesse Phillips wrote:


 What is your expected behavior? Throw an exception? You can't really
 append an absolute path to another.


Of course you can. I expect buildPath("/foo", "/bar") to result in 
"/foo/bar". That's how Ruby behaves.

-- 
/Jacob Carlborg
Jun 04 2017
next sibling parent reply Patrick Schluter <Patrick.Schluter bbox.fr> writes:
On Sunday, 4 June 2017 at 15:56:58 UTC, Jacob Carlborg wrote:

 On 2017-06-04 07:44, Jesse Phillips wrote:


 What is your expected behavior? Throw an exception? You can't 
 really
 append an absolute path to another.


 Of course you can. I expect buildPath("/foo", "/bar") to result 
 in "/foo/bar". That's how Ruby behaves.


buildPath("/usr/bin", "/usr/bin/gcc")

/usr/bin/usr/bin/gcc is obviously wrong. I think the semantic is 
not as illogical as it seem at first glance.
Jun 04 2017
parent reply Jacob Carlborg <doob me.com> writes:
On 2017-06-04 19:05, Patrick Schluter wrote:


 buildPath("/usr/bin", "/usr/bin/gcc")

 /usr/bin/usr/bin/gcc is obviously wrong.


Says who? It might be exactly what I want. The case that came up is 
inside DStep. The user provides a set of files C header to be translated 
to D modules. The user also provides a flag to indicate where to place 
the resulting files. I wanted to be able to keep the existing directory 
structure of the header files in the new target location. Example:

dstep -o result /usr/include/libxml2/libxml/*.h

The internals of DStep will do something like:

buildPath("result", "/usr/include/libxml2/libxml");

Which currently results in "/usr/include/libxml2/libxml". The end result 
is that DStep will try to write a file to "/usr/include/libxml2/libxml", 
which the user most likely will not have access to (without using sudo). 
I expected the result of buildPath to be 
"result/usr/include/libxml2/libxml".

-- 
/Jacob Carlborg
Jun 04 2017
parent Russel Winder via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> writes:
On Sun, 2017-06-04 at 21:32 +0200, Jacob Carlborg via Digitalmars-d-
learn wrote:

 On 2017-06-04 19:05, Patrick Schluter wrote:
=20

 buildPath("/usr/bin", "/usr/bin/gcc")
=20
 /usr/bin/usr/bin/gcc is obviously wrong.


=20
 Says who? It might be exactly what I want. The case that came up is=20
 inside DStep. The user provides a set of files C header to be
 translated=20
 to D modules. The user also provides a flag to indicate where to
 place=20
 the resulting files. I wanted to be able to keep the existing
 directory=20
 structure of the header files in the new target location. Example:


Says Guido et al. it seems, Python has in os.path and pathlib exactly
this behaviour.


 dstep -o result /usr/include/libxml2/libxml/*.h
=20
 The internals of DStep will do something like:
=20
 buildPath("result", "/usr/include/libxml2/libxml");
=20
 Which currently results in "/usr/include/libxml2/libxml". The end
 result=20
 is that DStep will try to write a file to
 "/usr/include/libxml2/libxml",=20
 which the user most likely will not have access to (without using
 sudo).=20
 I expected the result of buildPath to be=20
 "result/usr/include/libxml2/libxml".


Sadly Python tells us otherwise just as D does.

It is perhaps worth noting in passing that D path support seems very
like os.path and Python folk are giving that up in favour of pathlib.
Java/Kotlin/Groovy have also gone the same way. The implication is that
D needs better path support than it currently has to keep up with the
evolutions in other languages.

--=20
Russel.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
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=3D=3D
Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.winder ekiga.n=
et
41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel winder.org.uk
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder
Jun 12 2017
prev sibling parent reply Russel Winder via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> writes:
On Sun, 2017-06-04 at 17:56 +0200, Jacob Carlborg via Digitalmars-d-
learn wrote:

 On 2017-06-04 07:44, Jesse Phillips wrote:
=20

 What is your expected behavior? Throw an exception? You can't
 really
 append an absolute path to another.


=20
 Of course you can. I expect buildPath("/foo", "/bar") to result in=C2=A0
 "/foo/bar". That's how Ruby behaves.


And Python, Groovy, Java, Kotlin, Ceylon, C++, =E2=80=A6

--=20
Russel.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
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=3D=3D
Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.winder ekiga.n=
et
41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel winder.org.uk
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder
Jun 04 2017
parent reply Ryan Frame <dlang ryanjframe.com> writes:
On Sunday, 4 June 2017 at 18:15:36 UTC, Russel Winder wrote:

 On Sun, 2017-06-04 at 17:56 +0200, Jacob Carlborg via 
 Digitalmars-d- learn wrote:

 On 2017-06-04 07:44, Jesse Phillips wrote:
 

 What is your expected behavior? Throw an exception? You can't
 really
 append an absolute path to another.


 
 Of course you can. I expect buildPath("/foo", "/bar") to 
 result in "/foo/bar". That's how Ruby behaves.


 And Python, Groovy, Java, Kotlin, Ceylon, C++, …


Python 3.5.1 on my machine:

     >>> os.path.join("/asdf", "/bcd")
     '/bcd'
     >>> os.path.join("asdf", "/bcd")
     '/bcd'
Jun 11 2017
parent Russel Winder via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> writes:
On Sun, 2017-06-11 at 13:21 +0000, Ryan Frame via Digitalmars-d-learn
wrote:

 On Sunday, 4 June 2017 at 18:15:36 UTC, Russel Winder wrote:

 On Sun, 2017-06-04 at 17:56 +0200, Jacob Carlborg via=20
 Digitalmars-d- learn wrote:

 On 2017-06-04 07:44, Jesse Phillips wrote:
=20

 What is your expected behavior? Throw an exception? You can't
 really
 append an absolute path to another.


=20
 Of course you can. I expect buildPath("/foo", "/bar") to=20
 result in "/foo/bar". That's how Ruby behaves.


=20
 And Python, Groovy, Java, Kotlin, Ceylon, C++, =E2=80=A6


=20
 Python 3.5.1 on my machine:
=20
      >>> os.path.join("/asdf", "/bcd")
      '/bcd'
      >>> os.path.join("asdf", "/bcd")
      '/bcd'



documentation that this is the expected behaviour. Clearly, I have
never tried doing that in 20 years of playing with Python. And it has
never come up in 12 years of running Python workshops!

This behaviour is reinforced by pathlib which is the modern way of
doing paths in Python, replacing os.path:

    import pathlib

    p =3D pathlib.Path()
    p =3D p.joinpath('/', 'usr', '/local', '/bin')
    print(p)

result /bin.

So given Python is one of the targets for D, consistency of behaviour
implies D is currently doing the right thing.
=20
--=20
Russel.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
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=3D=3D
Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.winder ekiga.n=
et
41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel winder.org.uk
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder
Jun 12 2017