java - Bug in Path's .relativize() documentation or am I doing something blatantly wrong here? -

ok well, here fun. note "elements" here instance of pathelements, , these .resolve() , .relativize() fully tested , known work... links relevant method implementations path.resolve(), path.relativize()

extract of test method fails:

/*  * test part of path's .relativize() method:  *  * <p> 2 {@link #normalize normalized} paths <i>p</i> ,  * <i>q</i>, <i>q</i> not have root component,  * <blockquote>  * <i>p</i><tt>.relativize(</tt><i>p</i><tt>.resolve(</tt><i>q</i><tt>))  * .equals(</tt><i>q</i><tt>)</tt>  * </blockquote>  *  * unfortunately, turns out not true! whether p absolute or  * relative, indeed case path elements (root, names)  * same filesystem differs.  *  * path's .equals() requires 2 filesystems equal in  * order 2 paths equals, contract can not obeyed; or  * doing wrong.  */ @test(enabled = false) public void relativizeresolveroundrobinworks() {     /*      * in order set environment define mock      * filesystemprovider both our mock filesystems return when      * .provider() called.      *      * suppose same pathelementsfactory used; while      * code not written yet, there should 1 such factory per      * filesystemprovider anyway (which fed generated filesystem      * instances -- @ least that's plan).      *      * note test method assumes .equals() , .hashcode()      * not implemented on genericpath. such check filesystem      * same (this required path's equals()) , path      * elements same (this package's requirements).      */     final filesystemprovider fsprovider = mock(filesystemprovider.class);     final pathelementsfactory elementsfactory         = new unixpathelementsfactory();     final filesystem fsforp = mock(filesystem.class);     final filesystem fsforq = mock(filesystem.class);      when(fsforp.provider()).thenreturn(fsprovider);     when(fsforq.provider()).thenreturn(fsprovider);      /*      * path operated. contract says, has no root      * component.      */     final genericpath q = new genericpath(fsforq, elementsfactory,         new pathelements(null, new string[] { "q1", "q2" }));      /*      * path against both resolution , relativization      * performed. take 2 versions of it: non absolute 1 ,      * absolute one.      *      * note since use unixpathelementsfactory, equate      * absolute path (or not) path has root component (or not).      */     genericpath p;     // "rr" in "resolved, relativized"     genericpath rr;      final customsoftassertions soft = customsoftassertions.create();      /*      * try absolute version first...      */     p = new genericpath(fsforp, elementsfactory,         new pathelements("/", new string[] { "p1", "p2" }));     rr = (genericpath) p.relativize(p.resolve(q));      soft.assertthat(rr.getfilesystem())         .as("rr , q filesystems should same (p absolute)")         .issameas(q.getfilesystem());     soft.assertthat(rr.elements).hassamecontentsas(q.elements);      /*      * non absolute version      */     p = new genericpath(fsforp, elementsfactory,         new pathelements(null, new string[] { "p1", "p2" }));     rr = (genericpath) p.relativize(p.resolve(q));      soft.assertthat(rr.getfilesystem())         .as("rr , q filesystems should same (p not absolute)")         .issameas(q.getfilesystem());     soft.assertthat(rr.elements).hassamecontentsas(q.elements);      soft.assertall(); } 

this test fails with:

org.assertj.core.api.softassertionerror:  following 2 assertions failed: 1) [rr , q filesystems should same (p absolute)]  expecting:  <mock filesystem, hashcode: 1125642929> , actual:  <mock filesystem, hashcode: 1497261280> refer same object 2) [rr , q filesystems should same (p not absolute)]  expecting:  <mock filesystem, hashcode: 1125642929> , actual:  <mock filesystem, hashcode: 1497261280> refer same object 

and so!

• r = p.resolve(q) give path shares same filesystem p, not q;
• therefore, p.relativize(r) give path same filesystem p;
• but path contract requires in order 2 paths equal, share same filesystem.

and always false in scenario.

so, blatant bug in documentation or overlooking something?

a: documentation not mention paths other filesystem.

the documentation resolve , relativize not clear here. in case argument path different filesystem resolve , relativize must throw providermismatchexception. test should throw earlier.

the constraints on path can quite different filesystem filesystem. consider relativize case. should path can walk 1 filesystem disjoint filesystem ?

note: tested several filesystem implementations , throw in case.