Hello!
Consider this example:
--8<---------------cut here---------------start------------->8---
let x = derivation {
name = "x"; builder = ./foo.sh; system = builtins.currentSystem;
};
y = { b = x; };
in
x // y
--8<---------------cut here---------------end--------------->8---
Running ‘nix-instantiate --strict --eval-only --xml’ yields this:
--8<---------------cut here---------------start------------->8---
<?xml version='1.0' encoding='utf-8'?>
<expr>
<derivation drvPath="/nix/store/b1pmg2fhxnlnxy0z9hfglgyk66wpa2ar-x.drv"
outPath="/nix/store/fw6flnp42lqn9i62aknpch29sadds5pi-x">
<attr column="11" line="2" name="b"
path="/home/ludo/src/nixpkgs/maintainers/scripts/gnu/self-ref.nix">
<derivation drvPath="/nix/store/b1pmg2fhxnlnxy0z9hfglgyk66wpa2ar-x.drv"
outPath="/nix/store/fw6flnp42lqn9i62aknpch29sadds5pi-x">
<repeated />
</derivation>
</attr>
[...]
</derivation>
</expr>
--8<---------------cut here---------------end--------------->8---
When parsing this with SAX, the ‘repeated’ element is seen before the
first occurrence of the derivation, which is a problem: the program that
parses it doesn’t have anything to repeat yet.
I believe this patch fixes it:
--- nix/src/libexpr/expr-to-xml.cc~ 2010-05-31 12:59:38.000000000 +0200
+++ nix/src/libexpr/expr-to-xml.cc 2011-04-09 17:23:26.000000000 +0200
@@ -138,8 +138,8 @@ static void printTermAsXML(Expr e, XMLWr
XMLOpenElement _(doc, "derivation", xmlAttrs);
if (drvsSeen.find(e) == drvsSeen.end()) {
- drvsSeen.insert(e);
showAttrs(attrs, doc, context, drvsSeen, location);
+ drvsSeen.insert(e);
} else
doc.writeEmptyElement("repeated");
}
OK to apply, along with a test?
(For the record, I just encountered this problem for the first time with
‘buildInternalPythonModule’ in the Python 2.7 expression.)
Thanks,
Ludo’.
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