javascript: Unify simple parameter reference and node fallback.

* ravanan/command-line-tool.scm: Do not import (ravanan config), and
node from (gnu packages node).
(%worker-node): Move to (ravanan javascript).
(interpolate-parameter-references): Delete function.
(coerce-expression): Always call evaluate-parameter-reference
from (ravanan javascript).
* ravanan/work/command-line-tool.scm (evaluate-parameter-reference):
Delete function.
* ravanan/javascript.scm: Mention fallback to node in module
commentary. Import (ravanan config), (ravanan work command-line-tool),
and node from (gnu packages node).
(evaluate-simple-parameter-reference): Rename to
evaluate-parameter-reference.
(evaluate-parameter-reference-1, evaluate-parameter-reference): Add
expression-lib argument. Return regular values, not maybe-monadic
values.
(evaluate-using-node): New function.
* tests/javascript.scm ("evaluate parameter reference", "evaluate
parameter reference with string interpolation", "evaluate parameter
reference with string interpolation of JSON trees"): Update tests.
("evaluate parameter reference with node", "evaluate parameter
reference with string interpolation using node", "evaluate parameter
reference with string interpolation of JSON trees using node"): New
tests.

4 files changed, 138 insertions, 148 deletions

diff --git a/ravanan/command-line-tool.scm b/ravanan/command-line-tool.scm
index a789079..54a92cf 100644
--- a/ravanan/command-line-tool.scm
+++ b/ravanan/command-line-tool.scm
@@ -27,7 +27,6 @@
   #:use-module (ice-9 match)
   #:use-module ((gnu packages gnupg) #:select (guile-gcrypt))
   #:use-module ((gnu packages guile-xyz) #:select (guile-filesystem))
-  #:use-module ((gnu packages node) #:select (node))
   #:use-module (guix derivations)
   #:use-module (guix gexp)
   #:use-module (guix modules)
@@ -36,7 +35,6 @@
   #:use-module (guix search-paths)
   #:use-module (guix store)
   #:use-module (json)
-  #:use-module (ravanan config)
   #:use-module (ravanan javascript)
   #:use-module (ravanan job-state)
   #:use-module (ravanan reader)
@@ -85,10 +83,6 @@
     (else
      (assertion-violation batch-system "Unknown batch system"))))
 
-;; node executable for evaluating javascript on worker nodes
-(define %worker-node
-  (file-append node "/bin/node"))
-
 (define-immutable-record-type <formal-output>
   (formal-output id type binding)
   formal-output?
@@ -168,22 +162,6 @@ class. Else, return @code{#f}."
 @code{#f}."
   (string-contains str "$("))
 
-(define (interpolate-parameter-references str)
-  "Interpolate @var{str} with one or more parameter references into a javascript
-expression suitable for evaluation."
-  (string-join (map (lambda (token)
-                      (if (and (string-prefix? "$(" token)
-                               (string-suffix? ")" token))
-                          ;; Strip $(…).
-                          (substring token
-                                     (string-length "$(")
-                                     (- (string-length token)
-                                        (string-length ")")))
-                          ;; Surround with double quotes.
-                          (string-append "\"" token "\"")))
-                    (tokenize-parameter-references str))
-               " + "))
-
 (define* (coerce-expression expression #:optional context)
   "Coerce @var{expression} into a scheme JSON tree.
 
@@ -197,26 +175,8 @@ context and return the value. @var{context} must be an association list with
 keys @code{input}, @code{self} and @code{runtime}."
   (if (and (string? expression)
            (javascript-expression? expression))
-      (from-maybe
-       ;; Try evaluating expression as a simple parameter reference that uses a
-       ;; subset of javascript.
-       (evaluate-simple-parameter-reference expression context)
-       ;; Perhaps this is a more complex javascript expression. Fall back to node.
-       (if context
-           ;; Evaluate immediately.
-           (evaluate-parameter-reference %node
-                                         (interpolate-parameter-references expression)
-                                         (assq-ref context 'inputs)
-                                         'null
-                                         (list)
-                                         (list))
-           ;; Compile to a G-expression that evaluates expression.
-           #~(evaluate-parameter-reference #$%worker-node
-                                           #$(interpolate-parameter-references expression)
-                                           inputs
-                                           'null
-                                           runtime
-                                           (list))))
+      ;; Evaluate javascript expression.
+      (evaluate-parameter-reference expression context)
       ;; Not a javascript expression, but some other JSON tree. Return it as is.
       expression))
 
diff --git a/ravanan/javascript.scm b/ravanan/javascript.scm
index ad65828..47846df 100644
--- a/ravanan/javascript.scm
+++ b/ravanan/javascript.scm
@@ -20,7 +20,8 @@
 
 ;; CWL allows parameter references that use a subset of Javascript/ECMAScript
 ;; 5.1 syntax. This module implements that subset in scheme without resorting to
-;; a full-blown javascript engine.
+;; a full-blown javascript engine. In addition, it provides a fallback to the
+;; node javascript engine for more complex expressions.
 
 ;;; Code:
 
@@ -28,13 +29,18 @@
   #:use-module (srfi srfi-1)
   #:use-module (ice-9 match)
   #:use-module (ice-9 peg)
+  #:use-module ((gnu packages node) #:select (node))
   #:use-module (guix gexp)
   #:use-module (json)
-  #:use-module (ravanan work monads)
+  #:use-module (ravanan config)
+  #:use-module (ravanan work command-line-tool)
   #:use-module (ravanan work ui)
   #:use-module (ravanan work utils)
-  #:export (evaluate-simple-parameter-reference
-            tokenize-parameter-references))
+  #:export (evaluate-parameter-reference))
+
+;; node executable for evaluating javascript on worker nodes
+(define %worker-node
+  (file-append node "/bin/node"))
 
 (define-peg-pattern symbol body
   (+ (or (range #\a #\z)
@@ -65,45 +71,75 @@
 (define-peg-pattern parameter-reference all
   (and (ignore "(") symbol (* segment) (ignore ")")))
 
-(define* (evaluate-parameter-reference-1 expression context)
-  "Compile parameter reference @var{expression} to a G-expression that references
-the variables @code{inputs}, @code{self} or @code{runtime}. @var{expression}
-must strictly be a single parameter reference and will not be subject to string
-interpolation.
+(define* (evaluate-parameter-reference-1 expression context expression-lib)
+  "Compile parameter reference @var{expression} to a G-expression that evaluates
+it. The returned G-expression may reference the variables @code{inputs},
+@code{self} or @code{runtime}. @var{expression} must strictly be a single
+parameter reference and will not be subject to string interpolation.
 
 If @var{context} is not @code{#f}, evaluate the parameter reference in that
 context and return the value. @var{context} must be an association list with
 keys @code{\"inputs\"}, @code{\"self\"} and @code{\"runtime\"}.
 
-The returned value is maybe-monadic. If @var{expression} fails to parse,
-@code{Nothing} is returned."
-  (match (peg:tree (match-pattern parameter-reference expression))
-    ;; Special case for null
-    (('parameter-reference "null")
-     (just (if context
-               'null
-               #~'null)))
-    ;; Disallow referencing anything other than inputs, self or runtime.
-    (('parameter-reference (and (not (or "inputs" "self" "runtime"))
-                                symbol)
-                           _ ...)
-     (user-error "Invalid parameter reference; `~a' unknown"
-                 symbol))
-    ;; Parse parameter reference and produce a G-expression. The strange and
-    ;; complex matching pattern for segments accounts for how (ice-9 peg) adds
-    ;; an additional layer of parentheses to the tree when there are 2 or more
-    ;; segments.
-    (('parameter-reference symbol . (or (('segment segments) ...)
-                                        ((('segment segments) ...))))
-     (let ((segments (map (match-lambda
-                            (('index key) (string->number key))
-                            (key key))
-                          segments)))
-       (just (if context
-                 (apply json-ref context symbol segments)
-                 #~(json-ref #$symbol #$@segments)))))
-    ;; Perhaps this is a more complex javascript expression.
-    (#f %nothing)))
+@var{expression-lib} is a list of expressions evaluated before evaluating
+@var{expression}."
+  (match expression-lib
+    (()
+     (match (peg:tree (match-pattern parameter-reference expression))
+       ;; Special case for null
+       (('parameter-reference "null")
+        (if context
+            'null
+            #~'null))
+       ;; Disallow referencing anything other than inputs, self or runtime.
+       (('parameter-reference (and (not (or "inputs" "self" "runtime"))
+                                   symbol)
+                              _ ...)
+        (user-error "Invalid parameter reference; `~a' unknown"
+                    symbol))
+       ;; Parse parameter reference and produce a G-expression. The strange and
+       ;; complex matching pattern for segments accounts for how (ice-9 peg)
+       ;; adds an additional layer of parentheses to the tree when there are 2
+       ;; or more segments.
+       (('parameter-reference symbol . (or (('segment segments) ...)
+                                           ((('segment segments) ...))))
+        (let ((segments (map (match-lambda
+                               (('index key) (string->number key))
+                               (key key))
+                             segments)))
+          (if context
+              ;; Evaluate immediately.
+              (apply json-ref context symbol segments)
+              ;; Compile to a G-expression that evaluates expression.
+              #~(json-ref #$symbol #$@segments))))
+       ;; Perhaps this is a more complex javascript expression.
+       (#f
+        (evaluate-using-node expression context expression-lib))))
+    ;; expression-lib has been provided. Fall back to node.
+    (_
+     (evaluate-using-node expression context expression-lib))))
+
+(define (evaluate-using-node expression context expression-lib)
+  "This function is the same as @code{evaluate-parameter-reference-1} but uses
+the node javascript engine."
+  (define (set-variable name value)
+    (string-append name " = " (scm->json-string value) ";"))
+
+  (define preamble
+    (string-join (append expression-lib
+                         (filter-map (match-lambda
+                                       (((and (or "inputs" "self" "runtime")
+                                              name)
+                                         . value)
+                                        (set-variable name value))
+                                       (_ #f))
+                                     context))))
+
+  (if context
+      ;; Evaluate immediately.
+      (evaluate-javascript %node expression preamble)
+      ;; Compile to a G-expression that evaluates expression.
+      #~(evaluate-javascript #$%worker-node #$expression #$preamble)))
 
 (define (tokenize-parameter-references str)
   "Split @var{str} into tokens of parameter reference and literal strings."
@@ -117,7 +153,7 @@ The returned value is maybe-monadic. If @var{expression} fails to parse,
             (list)
             (list str)))))
 
-(define* (evaluate-simple-parameter-reference str #:optional context)
+(define* (evaluate-parameter-reference str #:optional context (expression-lib '()))
   "Compile parameter reference @var{str} to a G-expression that references
 the variables @code{inputs}, @code{self} or @code{runtime}. @var{str} may be
 subject to string interpolation.
@@ -126,37 +162,33 @@ If @var{context} is not @code{#f}, evaluate the parameter reference in that
 context and return the value. @var{context} must be an association list with
 keys @code{\"inputs\"}, @code{\"self\"} and @code{\"runtime\"}.
 
-The returned value is maybe-monadic. If any of the parameter references in
-@var{str} fail to parse, @code{Nothing} is returned."
+@var{expression-lib} is a list of expressions evaluated before evaluating
+@var{expression}."
   (define (evaluate-token token)
     (if (and (string-prefix? "$(" token)
              (string-suffix? ")" token))
         ;; Drop the leading "$" and evaluate.
-        (evaluate-simple-parameter-reference-1 (string-drop token 1)
-                                               context)
+        (evaluate-parameter-reference-1 (string-drop token 1)
+                                        context
+                                        expression-lib)
         ;; token is a string literal.
-        (just token)))
-
-  (maybe-let* ((evaluated-tokens
-                (fold (lambda (token maybe-result)
-                        (maybe-let* ((result maybe-result))
-                          (maybe-let* ((evaluated-token (evaluate-token token)))
-                            (just (cons evaluated-token result)))))
-                      (just (list))
-                      (tokenize-parameter-references str))))
-    (just (if context
-              ;; Evaluate immediately.
-              (string-join (map (lambda (token)
-                                  (if (string? token)
-                                      token
-                                      (scm->json-string (canonicalize-json token))))
-                                (reverse evaluated-tokens))
-                           "")
-              ;; Compile to a G-expression that interpolates parameter reference
-              ;; string.
-              #~(string-join (map (lambda (token)
-                                    (if (string? token)
-                                        token
-                                        (scm->json-string (canonicalize-json token))))
-                                  (list #$@(reverse evaluated-tokens)))
-                             "")))))
+        token))
+
+  (let ((evaluated-tokens (map evaluate-token
+                               (tokenize-parameter-references str))))
+    (if context
+        ;; Evaluate immediately.
+        (string-join (map (lambda (token)
+                            (if (string? token)
+                                token
+                                (scm->json-string (canonicalize-json token))))
+                          evaluated-tokens)
+                     "")
+        ;; Compile to a G-expression that interpolates parameter reference
+        ;; string.
+        #~(string-join (map (lambda (token)
+                              (if (string? token)
+                                  token
+                                  (scm->json-string (canonicalize-json token))))
+                            (list #$@evaluated-tokens))
+                       ""))))
diff --git a/ravanan/work/command-line-tool.scm b/ravanan/work/command-line-tool.scm
index a334285..4787e3d 100644
--- a/ravanan/work/command-line-tool.scm
+++ b/ravanan/work/command-line-tool.scm
@@ -36,8 +36,7 @@
             run-command
             sha1-hash
             checksum
-            evaluate-javascript
-            evaluate-parameter-reference))
+            evaluate-javascript))
 
 (define (value->string x)
   "Convert value @var{x} to a string."
@@ -206,20 +205,3 @@ status in @var{success-codes} as success. Error out otherwise."
                                 (format #f "--eval=~a console.log(\"%j\", ~a)"
                                         preamble expression))
       json->scm)))
-
-(define (evaluate-parameter-reference node expression inputs self runtime expression-lib)
-  "Evaluate parameter reference @var{expression} using
-@var{node}. @var{inputs}, @var{self} and @var{runtime} provide the
-context in which @var{expression} is evaluated. @var{expression-lib}
-is a list of expressions evaluated before evaluating @var{expression}."
-  (define (set-variable name value)
-    (format #f "~a = ~a;"
-            name
-            (scm->json-string value)))
-
-  (evaluate-javascript node
-                       expression
-                       (string-join (append expression-lib
-                                            (list (set-variable "inputs" inputs)
-                                                  (set-variable "self" self)
-                                                  (set-variable "runtime" runtime))))))
diff --git a/tests/javascript.scm b/tests/javascript.scm
index 5f23153..b6c4753 100644
--- a/tests/javascript.scm
+++ b/tests/javascript.scm
@@ -24,30 +24,46 @@
 
 (test-equal "evaluate parameter reference"
   "c"
-  (from-maybe
-   (evaluate-simple-parameter-reference "$(inputs.message['bar'][\"foo\"][2])"
-                                        '(("inputs" ("message" ("bar" ("foo" . #("a" "b" "c" "d")))))))
-   #f))
+  (evaluate-parameter-reference "$(inputs.message['bar'][\"foo\"][2])"
+                                '(("inputs" ("message" ("bar" ("foo" . #("a" "b" "c" "d"))))))))
 
 (test-equal "evaluate parameter reference with string interpolation"
   "24foo12foobar"
-  (from-maybe
-   (evaluate-simple-parameter-reference "$(runtime.cores)foo$(inputs.threads)$(inputs.output_filename)"
-                                        '(("inputs"
-                                           ("threads" . 12)
-                                           ("output_filename" . "foobar"))
-                                          ("runtime" ("cores" . 24))))
-   #f))
+  (evaluate-parameter-reference "$(runtime.cores)foo$(inputs.threads)$(inputs.output_filename)"
+                                '(("inputs"
+                                   ("threads" . 12)
+                                   ("output_filename" . "foobar"))
+                                  ("runtime" ("cores" . 24)))))
 
 (test-equal "evaluate parameter reference with string interpolation of JSON trees"
   "foo[0,1,2,3]{\"bar\":2,\"foo\":1}"
-  (from-maybe
-   (evaluate-simple-parameter-reference "foo$(inputs.vector)$(inputs.object)"
-                                        '(("inputs"
-                                           ("object"
-                                            ("foo" . 1)
-                                            ("bar" . 2))
-                                           ("vector" . #(0 1 2 3)))))
-   #f))
+  (evaluate-parameter-reference "foo$(inputs.vector)$(inputs.object)"
+                                '(("inputs"
+                                   ("object"
+                                    ("foo" . 1)
+                                    ("bar" . 2))
+                                   ("vector" . #(0 1 2 3))))))
+
+(test-equal "evaluate parameter reference with node"
+  "3"
+  (evaluate-parameter-reference "$(inputs.n + 1)"
+                                '(("inputs" ("n" . 2)))))
+
+(test-equal "evaluate parameter reference with string interpolation using node"
+  "24foo24foobar"
+  (evaluate-parameter-reference "$(runtime.cores)foo$(inputs.threads*2)$(inputs.output_filename)"
+                                '(("inputs"
+                                   ("threads" . 12)
+                                   ("output_filename" . "foobar"))
+                                  ("runtime" ("cores" . 24)))))
+
+(test-equal "evaluate parameter reference with string interpolation of JSON trees using node"
+  "foo[0,1,2,3]{\"bar\":2,\"foo\":1}20"
+  (evaluate-parameter-reference "foo$(inputs.vector)$(inputs.object)$(inputs.object.foo*20)"
+                                '(("inputs"
+                                   ("object"
+                                    ("foo" . 1)
+                                    ("bar" . 2))
+                                   ("vector" . #(0 1 2 3))))))
 
 (test-end "javascript")