ddn.data.json5

Feature switches for JSON5 support.

Policy controlling writer defaults and parser behavior.

This struct is named Json5Policy following the convention of format-specific policy structs (JsonPolicy, SdlPolicy). The CfParserConfig struct uses a different naming pattern for historical reasons (it predates the policy naming convention and has additional configuration beyond parsing behavior).

Unlike JsonPolicy which uses a JsonDuplicateKeyPolicy enum with three options (LAST_WINS, FIRST_WINS, ERROR), this struct uses a simple boolean. This is intentional: JSON5 is designed as a more lenient format for human-authored configuration files, where strict duplicate detection (ERROR) is rarely desired. The boolean provides a simpler API for the common case of choosing between first-wins and last-wins semantics. When useStrictJsonParser is enabled, the boolean maps to the corresponding enum value in the underlying JsonPolicy.

A non-throwing error report produced by the JSON5 parser/writer.

Quote style used by the JSON5 writer.

Output mode for the writer.

Writer formatting options for JSON5 emission.

Fields:

• pretty: enable multi-line pretty printing with indentation.
• indentWidth: number of spaces per indentation level (used only when pretty).
• quoteStyle: whether strings are emitted with single or double quotes.
• asciiOnly: when true, escape non-ASCII as \uXXXX or \u{...}.
• sortKeys: when true, object keys are emitted sorted for deterministic output.
• maxDepth: maximum nesting depth allowed during writing; when exceeded, the writer emits null.
• trailingCommas: when true, pretty mode emits a trailing comma after the last array element

and the last object property; ignored in compact mode.

Reusable scratch buffers for JSON5/JSON writing.

This structure allows caller-controlled reuse of temporary allocations across repeated serializations.

Currently used for:

• Deterministic object serialization (sortKeys == true) via per-depth key buffers.

Floating-point formatting mode used by the JSON5 writer.

Controls how floating-point negative zero is emitted.

Reviver callback used to transform parsed values.

The callback is invoked in post-order (children first), similarly to JavaScript JSON.parse(text, reviver).

Arguments:

• key: Object key / array index (as decimal string). Root is passed as `""`.
• value: Current value.

The return value is the replacement value.

Kind of a JSON5 patch operation.

A single JSON5 patch operation.

The path is a JSON Pointer-like path using `/` separators.

• Root is `""`.
• ~1 decodes to `/`.
• ~0 decodes to `~`.

Patch application error.

Result of a streaming JSON5 parse attempt.

Incremental/streaming JSON5 parser that accepts input in chunks.

This API is intended for large inputs or network streams where the complete document may not be available at once.

Notes:

• The parser produces at most one root JSON5 value.
• After a successful parse (Json5StreamResult.OK), the instance becomes done;

call reset() to parse another document.

• When finish() has not been called yet, parse failures that look like

“unexpected end of input” are reported as NEED_MORE.

import ddn.data.json5 : Json5StreamParser, Json5StreamResult, Json5Error;
import ddn.var : var;

Json5StreamParser sp;
sp.push("{a:1,");
var v; Json5Error err;
assert(sp.tryParse(v, err) == Json5StreamResult.NEED_MORE);
sp.push("b:2}");
assert(sp.tryParse(v, err) == Json5StreamResult.OK);
assert(v["b"].as!long == 2);

Callbacks for SAX-style JSON5 parsing.

Any callback may be left null to ignore that event.

Event semantics:

• onObjectStart / onObjectEnd are emitted for `{` / `}`.
• onArrayStart / onArrayEnd are emitted for `[` / `]`.
• onKey is emitted for each object property key, before its value.
• onValue is emitted for scalar values only (null/bool/number/string).

Kinds of JSON5 tokens.

A single JSON5 token.

High-performance JSON5 lexer over a UTF‑8 buffer.

• Skips BOM, whitespace, and comments.
• Returns slices for identifiers, strings, and numbers without allocating.
• Tracks line/column for diagnostics.

A small, non-throwing JSON5 recursive-descent parser that builds ddn.var directly.

Create an instance with input and policy, then call parseRoot(out var) to parse a value. On failure, parseRoot returns false and populates the provided Json5Error with line/column and a brief message.

Internal CDM-producing parser structure that reuses the existing lexer.

This struct is used by parseJson5Cdm to produce CdmDocument instances while preserving comments, source locations, and formatting metadata.

Parse JSON5 text into a CDM document.

Preserves comments, source locations, and formatting metadata for roundtrip fidelity.

import ddn.data.json5;
import ddn.data.cdm;

auto doc = parseJson5Cdm(`{
   // Server configuration
   host: "localhost",
   port: 8080
}`);
assert(doc.root.isObject);
assert(doc.root["host"].as!string == "localhost");

Default feature set enabled by the JSON5 reader/writer.