option to allow trailing characters while parsing

Project.toml

@@ -1,6 +1,6 @@
 name = "JSON"
 uuid = "682c06a0-de6a-54ab-a142-c8b1cf79cde6"
-version = "1.4.0"
+version = "1.5.0"
 
 [deps]
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"

src/lazy.jl

@@ -59,6 +59,7 @@ Currently supported keyword arguments include:
   - `inf::String = "Infinity"`: the string that will be used to parse `Inf` if `allownan=true`
   - `nan::String = "NaN"`: the string that will be sued to parse `NaN` if `allownan=true`
   - `jsonlines::Bool = false`: whether the JSON input should be treated as an implicit array, with newlines separating individual JSON elements with no leading `'['` or trailing `']'` characters. Common in logging or streaming workflows. Defaults to `true` when used with `JSON.parsefile` and the filename extension is `.jsonl` or `ndjson`. Note this ensures that parsing will _always_ return an array at the root-level.
+  - `isroot::Bool = true`: whether this is the root LazyValue encompassing the entire json buffer. If `false` parses only the first JSON value and ignores trailing characters.
 
 Note that validation is only fully done on `null`, `true`, and `false`,
 while other values are only lazily inferred from the first non-whitespace character:
@@ -88,7 +89,7 @@ lazyfile(file; jsonlines::Union{Bool, Nothing}=nothing, kw...) = open(io -> lazy
 
 @doc (@doc lazy) lazyfile
 
-function lazy(buf::Union{AbstractVector{UInt8}, AbstractString}; kw...)
+function lazy(buf::Union{AbstractVector{UInt8}, AbstractString}; isroot::Bool=true, kw...)
     if !applicable(pointer, buf, 1) || (buf isa AbstractVector{UInt8} && !isone(only(strides(buf))))
         if buf isa AbstractString
             buf = String(buf)
@@ -116,7 +117,7 @@ function lazy(buf::Union{AbstractVector{UInt8}, AbstractString}; kw...)
     # detect and ignore UTF-8 BOM
     pos = (len >= 3 && getbyte(buf, pos) == 0xef && getbyte(buf, pos + 1) == 0xbb && getbyte(buf, pos + 2) == 0xbf) ? pos + 3 : pos
     @nextbyte
-    return _lazy(buf, pos, len, b, LazyOptions(; kw...), true)
+    return _lazy(buf, pos, len, b, LazyOptions(; kw...), isroot)
 
 @label invalid
     invalid(error, buf, pos, Any)

src/parse.jl

@@ -15,6 +15,7 @@ Currently supported keyword arguments include:
   * `inf`: string to use for `Inf` (default: `"Infinity"`)
   * `nan`: string to use for `NaN` (default: `"NaN"`)
   * `jsonlines`: treat the `json` input as an implicit JSON array, delimited by newlines, each element being parsed from each row/line in the input
+  * `isroot`: whether this is the root LazyValue encompassing the entire json buffer. If `false` parses only the first JSON value and ignores trailing characters. (default: `true`)
   * `dicttype`: a custom `AbstractDict` type to use instead of `$DEFAULT_OBJECT_TYPE` as the default type for JSON object materialization
   * `null`: a custom value to use for JSON null values (default: `nothing`)
   * `style`: a custom `StructUtils.StructStyle` subtype instance to be used in calls to `StructUtils.make` and `StructUtils.lift`. This allows overriding

test/parse.jl

@@ -771,3 +771,18 @@ end
     @test_throws ArgumentError JSON.parse("{}", Tuple{Int, Int, Int})
     @test_throws ArgumentError JSON.parse("{\"a\":1,\"b\":2}", Tuple{Int, Int, Int})
 end
+
+@testset "isroot=false allows trailing" begin
+    # default behavior: trailing content causes an error
+    @test_throws ArgumentError JSON.parse("{\"hello\": \"world\"} asdaa")
+    @test_throws ArgumentError JSON.parse("[1,2,3] extra")
+    @test_throws ArgumentError JSON.parse("123 {}")
+
+    # isroot=false: trailing content is ignored
+    @test JSON.parse("{\"hello\": \"world\"} asdaa", isroot=false) == JSON.Object("hello" => "world")
+    @test JSON.parse("[1,2,3] extra", isroot=false) == Any[1, 2, 3]
+    @test JSON.parse("123 {}", isroot=false) == 123
+
+    # isroot=false with typed parse
+    @test JSON.parse("{\"a\": 1, \"b\": 2.0, \"c\": \"hi\"} trailing", D; isroot=false) == D(1, 2.0, "hi")
+end