Support ${foob-bar} and ${foo+bar}.

* gash/environment.scm (variable): Add default parameter.
(variable-or, variable-and): New function.
* test/07-variable-or.sh: Test it.
* test/07-variable-or-not.sh:
* test/08-variable-and.sh:
* test/08-variable-and-not.sh:

check.sh

@@ -29,6 +29,12 @@ tests="
 06-compound-word
 06-command-compound-word
 
+07-variable-or
+07-variable-not-or
+
+08-variable-and
+08-variable-not-and
+
 10-if
 10-if-false
 10-if-word-variable

gash/environment.scm

@@ -29,6 +29,8 @@
             set-shell-opt!
             shell-opt?
             variable
+            variable-and
+            variable-or
             ))
 
 ;; FIXME: export/env vs set
@@ -50,14 +52,21 @@
              (assoc-set! %global-variables name value))
        #t))
 
-(define (variable name)
+(define* (variable name #:optional (default ""))
   (let ((name (if (string-prefix? "$" name) (string-drop name 1) name)))
     (or (assoc-ref %global-variables name)
         (if (shell-opt? "nounset") (begin
                                      ;; TODO: throw/error
                                      (format (current-error-port) "gash: ~a: unbound variable\n" name)
                                      #f)
-            ""))))
+            default))))
+
+(define (variable-or name default)
+  (variable name default))
+
+(define (variable-and name default)
+  (let ((value (variable name #f)))
+    (and value default)))
 
 (define (set-shell-opt! name set?)
   (let* ((shell-opts (variable "SHELLOPTS"))

gash/peg.scm

@@ -212,30 +212,28 @@
      filename         <-- word
      name             <-- identifier
      identifier       <-  [_a-zA-Z][_a-zA-Z0-9]*
-     oldword             <-  substitution / assignment / number / variable / delim / literal
-
-     word-for-test-assign-sh        <-- assignment / (delim / number / variable / literal)+
-     word-for-test-if2-sh            <-- assignment / delim / (number / variable / literal)+
-
-     word    <-- assignment / (delim / number / variable / literal)+
-
+     word             <-- assignment / delim / (number / variable / brace-variable / literal)+
 
      number           <-- [0-9]+
      lsubst           <   '$('
      rsubst           <   ')'
      tick             <   '`'
      substitution     <-- lsubst script rsubst / tick script tick
-     assignment       <-- name assign (substitution / word)*
+     assignment       <-- name assign rhs
+     rhs              <-  (substitution / word)*
      assign           <   '='
-     dollar           <-  '$'
-     literal          <-- (!tick !dollar !pipe !semi !par !nl !sp .)+
-     variable         <-- dollar (dollar / '*' / '?' / '@' / [0-9] / identifier / ([{] (![}] .)+ [}]))
+     dollar           <   '$'
+     literal          <-- (!tick !dollar !pipe !semi !par !nl !sp !rbrace .)+
+     variable         <-- dollar ('$' / '*' / '?' / '@' / [0-9] / identifier)
+     brace-variable   <-  dollar lbrace (variable-or / variable-and / identifier) rbrace
+     variable-and     <-- identifier plus rhs
+     variable-or      <-- identifier minus rhs
      delim            <-  singlequotes / doublequotes / substitution
      sq               <   [']
      dq               <   [\"]
      bt               <   [`]
      singlequotes     <-- sq  (doublequotes / (!sq .))* sq
-     doublequotes     <-- dq (singlequotes / substitution / variable / (!dq .))* dq
+     doublequotes     <-- dq (singlequotes / substitution / variable / variable-and-or / (!dq .))* dq
      break            <-  amp / semi !semi
      separator        <-  (sp* break ws*) / ws+
      sequential-sep   <-  (semi !semi ws*) / ws+
@@ -243,6 +241,10 @@
      semi             <   ';'
      lpar             <   '('
      rpar             <   ')'
+     lbrace           <   [{]
+     rbrace           <   [}]
+     plus             <   [+]
+     minus            <   '-'
      par              <   lpar / rpar
      nl               <   '\n'
      sp               <   [\t ]
@@ -282,6 +284,9 @@
     ((('literal _ ...) _ ...) (map transform (flatten ast)))
     ((('pipeline _ ...) _ ...) (map transform (flatten ast)))
     ((('singlequotes _ ...) _ ...) (map transform (flatten ast)))
+
+    ((('word _ ...) ('word _ ...)) (transform (cons 'word ast)))
+
     ((('word _ ...) _ ...) (map transform (flatten ast)))
 
     (('script ('pipeline ('command command ... (word (literal "&")))))

test/07-variable-not-or.sh

@@ -0,0 +1,2 @@
+foo=baz
+echo ${foo-bar}

test/07-variable-not-or.stdout

@@ -0,0 +1 @@
+baz

test/07-variable-or.sh

@@ -0,0 +1 @@
+echo ${foo-bar}

test/07-variable-or.stdout

@@ -0,0 +1 @@
+bar

test/08-variable-and.sh

@@ -0,0 +1,2 @@
+foo=baz
+echo ${foo+bar}

test/08-variable-and.stdout

@@ -0,0 +1 @@
+bar

test/08-variable-not-and.sh

@@ -0,0 +1 @@
+echo ${foo+bar}

test/08-variable-not-and.stdout

@@ -0,0 +1 @@
+