improve definition and tests of fromstream function

Author: itchyny

builtin.go

@@ -96,17 +96,17 @@ def truncate_stream(f):
   . as $n | null | f |
   if .[0] | length > $n then .[0] |= .[$n:] else empty end;
 def fromstream(f):
-  { x: null, e: false } as $init |
-  foreach f as $i (
-    $init;
-    if .e then $init end |
-    if $i | length == 2 then
-      setpath(["e"]; $i[0] | length == 0) |
-      setpath(["x"] + $i[0]; $i[1])
+  foreach f as $pv (
+    null;
+    if .e then null end |
+    $pv as [$p, $v] |
+    if $pv | length == 2 then
+      setpath(["v"] + $p; $v) |
+      setpath(["e"]; $p | length == 0)
     else
-      setpath(["e"]; $i[0] | length == 1)
+      setpath(["e"]; $p | length == 1)
     end;
-    if .e then .x else empty end
+    if .e then .v else empty end
   );
 def tostream:
   path(def r: (.[]? | r), .; r) as $p |

builtin.jq

@@ -4479,13 +4479,16 @@
 - name: fromstream function
   args:
     - -c
-    - 'fromstream(0,1,2|truncate_stream([[0],1],[[1,0],2],[[1,0]],[[1]]))'
+    - 'fromstream(range(5) | truncate_stream({x:[1,{y:[2]},3],z:[4]} | tostream))'
   input: 'null'
   expected: |
-    [1,[2]]
+    {"x":[1,{"y":[2]},3],"z":[4]}
+    [1,{"y":[2]},3]
+    [4]
+    {"y":[2]}
     [2]
 
-- name: stream function
+- name: tostream function
   args:
     - -c
     - 'tostream'
@@ -5975,17 +5978,28 @@
     [["a",2]]
     [["a"]]
 
-- name: inputs function with stream option and truncate_stream function
+- name: inputs function with stream option and fromstream function
   args:
     - -n
+    - -c
     - --stream
-    - 'fromstream(1 | truncate_stream(inputs) | select(length > 1) | .[0] |= .[1:])'
-  input: '{"a":[1,true,null,"x"]}'
+    - 'fromstream(inputs)'
+  input: 'null [false] {"x":[null]}'
   expected: |
-    1
-    true
     null
-    "x"
+    [false]
+    {"x":[null]}
+
+- name: inputs function with stream option and truncate_stream function
+  args:
+    - -n
+    - -c
+    - --stream
+    - 'fromstream(1 | truncate_stream(inputs))'
+  input: '{"x":[1,{"y":[2]},3],"z":[4]}'
+  expected: |
+    [1,{"y":[2]},3]
+    [4]
 
 - name: inputs function with stream option
   args: