[builtin/json] Support type_errors=false

Use it in the Hay example!

Author: Andy C

data_lang/j8.py

@@ -577,6 +577,9 @@ def Print(self, val, level=0):
 
                 if self.options & NON_DATA_IS_ERROR:
                     raise error.Encode("Can't encode value of type Obj")
+                elif self.options & NON_DATA_IS_NULL:
+                    self.buf.write('null')
+                    return
 
                 # Cycle detection, only for containers that can be in cycles
                 heap_id = HeapValueId(val)
@@ -612,6 +615,8 @@ def Print(self, val, level=0):
                 if self.options & NON_DATA_IS_ERROR:
                     raise error.Encode("Can't serialize object of type %s" %
                                        ValType(val))
+                elif self.options & NON_DATA_IS_NULL:
+                    self.buf.write('null')
                 else:
                     # Similar to = operator, ui.DebugPrint()
                     # TODO: that prints value.Range in a special way

doc/ref/chap-builtin-cmd.md

@@ -665,8 +665,10 @@ When a block is long, the former is more readable.
 Write JSON:
 
     var d = {name: 'bob', age: 42}
-    json write (d)           # default indentation of 2
-    json write (d, space=0)  # no indentation
+    json write (d)                     # default indent of 2, type errors
+    json write (d, space=0)            # no indent
+    json write (d, type_errors=false)  # non-serializable types become null
+                                       # (e.g. Obj, Proc, Eggex)
 
 Read JSON:
 

doc/ref/chap-builtin-func.md

@@ -301,7 +301,13 @@ Add indentation by passing the `space` param:
     $ = toJson([42], space=2)
     (Str)   "[\n  42\n]"
 
-Similar to `json write (x)`, except the default value of `space` is 0.
+Turn non-serializable types into `null`, instead of raising an error:
+
+    $ = toJson(/d+/, type_errors=false)
+    (Str)   'null'
+
+The `toJson()` function is to `json write (x)`, except the default value of
+`space` is 0.
 
 See [err-json-encode][] for errors.
 

spec/hay.test.sh

@@ -837,7 +837,7 @@ Package cpython {
 #
 # When type_errors=false (default), any unserializable value becomes null
 
-echo 'json write (_hay())' > stage-1.ysh
+echo 'json write (_hay(), type_errors=false)' > stage-1.ysh
 
 # Stage 1
 
@@ -867,7 +867,6 @@ build_proc
   ;
 
 
-
 ## STDOUT:
 a
 ## END

spec/ysh-json.test.sh

@@ -1249,3 +1249,37 @@ json write (assoc)
   }
 }
 ## END
+
+#### type_errors=false
+
+var o = Obj.new({}, null)
+
+#json write (o)
+json write (o, type_errors=false)
+
+var pat = /d+/
+#json write (pat)
+json write (pat, type_errors=false)
+
+var d = {key: pat, key2: o}
+json write (d, type_errors=false)
+
+echo
+
+echo $[toJson(o, type_errors=false)]
+echo $[toJson8(o, type_errors=false)]
+echo $[toJson8(d, type_errors=false)]
+
+## STDOUT:
+null
+null
+{
+  "key": null,
+  "key2": null
+}
+
+null
+null
+{"key":null,"key2":null}
+## END
+