Diff stdlib

import "std/diff" exposes line-oriented diff helpers and a structural review diff backed by hostlib tree-sitter parsing.

structural_diff — syntax-aware review diff

structural_diff(path_a, path_b, options?) compares two source files by syntax tree and returns a human-consumable structure. It is not a patch format; apply and staging flows should keep using unified line diffs.

options may be a language string:

import { structural_diff } from "std/diff"

let result = structural_diff("before.rs", "after.rs", "rust")

or a dict:

let result = structural_diff(
  "before.rs",
  "after.rs",
  {language: "rust", max_bytes: 1048576, max_nodes: 20000, max_graph_edges: 20000000},
)

When both files parse and stay under the limits, the result has result: "ok", mode: "structural", changed, changes, and a summary. Each change is one of insert, delete, replace, or move and carries before / after row-column spans plus small text snippets for renderer labels.

If the grammar cannot be inferred, parsing reports errors, or a size limit trips, the function silently returns result: "fallback" with mode: "line" and a line_diff payload. This lets TUI/GUI renderers degrade predictably without switching to a mutation-oriented patch path.

Line helpers

• diff_lines(before, after) returns line-level operations and counts.
• unified_diff(before, after, options?) renders a unified diff string.
• colorize_diff(diff_text, options?) applies ANSI color to unified diff text.
• diff_summary(before, after) returns compact line-change counts.
• render_diff_stat(entries, options?) renders a small per-file stat table.