gexp: Add 'local-file'.

* guix/gexp.scm (<local-file>): New record type.
  (local-file): New procedure.
  (local-file-compiler): New compiler.
  (gexp->sexp) <struct? thing>: Handle the case where 'lower' returns a
  file name.
  (text-file*): Update docstring.local-file doc
* tests/gexp.scm ("one local file", "gexp->derivation, local-file"): New
  tests.
* doc/guix.texi (G-Expressions): Mention local files early.  Document
  'local-file'.  Update 'text-file*' documentation.

1 files changed, 43 insertions, 4 deletions

diff --git a/guix/gexp.scm b/guix/gexp.scm
index 01290dba18..2492974d8f 100644
--- a/guix/gexp.scm
+++ b/guix/gexp.scm
@@ -31,6 +31,8 @@
 
             gexp-input
             gexp-input?
+            local-file
+            local-file?
 
             gexp->derivation
             gexp->file
@@ -135,6 +137,37 @@ cross-compiling.)"
 
 
 ;;;
+;;; Local files.
+;;;
+
+(define-record-type <local-file>
+  (%local-file file name recursive?)
+  local-file?
+  (file       local-file-file)                    ;string
+  (name       local-file-name)                    ;string
+  (recursive? local-file-recursive?))             ;Boolean
+
+(define* (local-file file #:optional (name (basename file))
+                     #:key (recursive? #t))
+  "Return an object representing local file FILE to add to the store; this
+object can be used in a gexp.  FILE will be added to the store under NAME--by
+default the base name of FILE.
+
+When RECURSIVE? is true, the contents of FILE are added recursively; if FILE
+designates a flat file and RECURSIVE? is true, its contents are added, and its
+permission bits are kept.
+
+This is the declarative counterpart of the 'interned-file' monadic procedure."
+  (%local-file file name recursive?))
+
+(define-gexp-compiler (local-file-compiler (file local-file?) system target)
+  ;; "Compile" FILE by adding it to the store.
+  (match file
+    (($ <local-file> file name recursive?)
+     (interned-file file name #:recursive? recursive?))))
+
+
+;;;
 ;;; Inputs & outputs.
 ;;;
 
@@ -453,8 +486,13 @@ and in the current monad setting (system type, etc.)"
         (($ <gexp-input> (? struct? thing) output n?)
          (let ((lower  (lookup-compiler thing))
                (target (if (or n? native?) #f target)))
-           (mlet %store-monad ((drv (lower thing system target)))
-             (return (derivation->output-path drv output)))))
+           (mlet %store-monad ((obj (lower thing system target)))
+             ;; OBJ must be either a derivation or a store file name.
+             (return (match obj
+                       ((? derivation? drv)
+                        (derivation->output-path drv output))
+                       ((? string? file)
+                        file))))))
         (($ <gexp-input> x)
          (return x))
         (x
@@ -809,8 +847,9 @@ its search path."
 
 (define* (text-file* name #:rest text)
   "Return as a monadic value a derivation that builds a text file containing
-all of TEXT.  TEXT may list, in addition to strings, packages, derivations,
-and store file names; the resulting store file holds references to all these."
+all of TEXT.  TEXT may list, in addition to strings, objects of any type that
+can be used in a gexp: packages, derivations, local file objects, etc.  The
+resulting store file holds references to all these."
   (define builder
     (gexp (call-with-output-file (ungexp output "out")
             (lambda (port)