Reimplement split/1 intrinsic

Author: thaliaarchi

README.md

@@ -166,7 +166,7 @@ Note that the tests are meant to be used with jq 1.7.
   - [x] `select(f)`
   - [x] `setpath` (passthrough)
   - [x] `sort`, `sort_by(f)`
-  - [ ] `split($s)`
+  - [x] `split($s)`
   - [x] `split($re; flags)`
   - [x] `splits($re)`, `splits($re; flags)`
   - [x] `startswith($s)`

jqjq.jq

@@ -1924,6 +1924,9 @@ def scalars: select(_is_scalar);
 
 def add: reduce .[] as $v (null; . + $v);
 
+def startswith($s): .[0:$s | length] == $s;
+def endswith($s): .[$s | -length:] == $s;
+
 def _nwise($n):
   def n:
     if length <= $n then .
@@ -1940,6 +1943,22 @@ def splits($re; flags):
 def splits($re): splits($re; null);
 def split($re; flags): [splits($re; flags)];
 
+def _strsplit($delim; $acc):
+  if . == \"\" then $acc
+  elif startswith($delim) then
+    $acc, (.[$delim | length:] | _strsplit($delim; \"\"))
+  else .[:1] as $c | .[1:] | _strsplit($delim; $acc + $c)
+  end;
+def _strsplit0:
+  if . == \"\" then empty else .[:1], (.[1:] | _strsplit0) end;
+def split($s):
+  if type != \"string\" or ($s | type != \"string\") then
+    error(\"split input and separator must be strings\")
+  elif . == \"\" then []
+  elif $s == \"\" then [_strsplit0]
+  else [_strsplit($s; \"\")]
+  end;
+
 def join($s):
   if length == 0 then \"\"
   else
@@ -2103,9 +2122,6 @@ def nth($n): .[$n];
 
 def isempty(f): [limit(1; f)] == [];
 
-def startswith($s): .[0:$s | length] == $s;
-def endswith($s): .[$s | -length:] == $s;
-
 def _strindices($i):
   . as $s | [range(length) | select($s[.:] | startswith($i))];
 def indices($i):

jqjq.test

@@ -979,6 +979,14 @@ null
 "a,b|c,d,e||f,g,h,|,|,i,j"
 [1,3,22,19,[1,5,7,12,14,16,18,20,22],[3,9,10,17,19]]
 
+[.[] | split(", ")]
+["", "a,b, c, d, e,f", ", a,b, c, d, e,f, "]
+[[],["a,b","c","d","e,f"],["","a,b","c","d","e,f",""]]
+
+[.[] | split("")]
+["", "abc"]
+[[],["a","b","c"]]
+
 # SKIP_JQ
 # test below does not work with standard jq because of missing features or bugs