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* Big cleanup of the semantics of paths, strings, contexts, string

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concatenation and string coercion.  This was a big mess (see
  e.g. NIX-67).  Contexts are now folded into strings, so that they
  don't cause evaluation errors when they're not expected.  The
  semantics of paths has been clarified (see nixexpr-ast.def).
  toString() and coerceToString() have been merged.

  Semantic change: paths are now copied to the store when they're in a
  concatenation (and in most other situations - that's the
  formalisation of the meaning of a path).  So

    "foo " + ./bla

  evaluates to "foo /nix/store/hash...-bla", not "foo
  /path/to/current-dir/bla".  This prevents accidental impurities, and
  is more consistent with the treatment of derivation outputs, e.g.,
  `"foo " + bla' where `bla' is a derivation.  (Here `bla' would be
  replaced by the output path of `bla'.)
This commit is contained in:
Eelco Dolstra 2006-10-16 15:55:34 +00:00
parent 4c9aa821b9
commit d7efd76394
17 changed files with 331 additions and 396 deletions
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23
src/libexpr/eval.hh
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@ -60,17 +60,26 @@ Expr strictEvalExpr(EvalState & state, Expr e,
bool canonicalise = false);
/* Specific results. */
string evalString(EvalState & state, Expr e);
Path evalPath(EvalState & state, Expr e);
string evalString(EvalState & state, Expr e, PathSet & context);
string evalStringNoCtx(EvalState & state, Expr e);
int evalInt(EvalState & state, Expr e);
bool evalBool(EvalState & state, Expr e);
ATermList evalList(EvalState & state, Expr e);
ATerm coerceToString(Expr e);
/* Contexts. */
string coerceToStringWithContext(EvalState & state,
ATermList & context, Expr e, bool & isPath);
Expr wrapInContext(ATermList context, Expr e);
/* Flatten nested lists into a single list (or expand a singleton into
a list). */
ATermList flattenList(EvalState & state, Expr e);
/* String coercion. Converts strings, paths and derivations to a
string. If `coerceMore' is set, also converts nulls, integers,
booleans and lists to a string. */
string coerceToString(EvalState & state, Expr e, PathSet & context,
bool coerceMore = false, bool copyToStore = true);
/* Path coercion. Converts strings, paths and derivations to a path.
The result is guaranteed to be an canonicalised, absolute path.
Nothing is copied to the store. */
Path coerceToPath(EvalState & state, Expr e, PathSet & context);
/* Automatically call a function for which each argument has a default
value or has a binding in the `args' map. Note: result is a call,