fabricatio-diff 0.4.0

An extension of fabricatio, which brings up the diff edit capabilities

fabricatio-diff

MIT

Intelligent diff-based editing for LLM-driven text transformations. Combines fuzzy line matching, hashline-anchored edits, and LLM-generated search-and-replace operations into a single package.

Installation

This package is part of the fabricatio monorepo and can be installed as an optional dependency:

pip install fabricatio[diff]
# or
uv pip install fabricatio[diff]

For a full installation:

pip install fabricatio[full]
# or
uv pip install fabricatio[full]

Overview

fabricatio-diff provides two complementary layers for text editing:

1. Rust-accelerated primitive operations — hashline anchoring, fuzzy line matching, unified diffs, and similarity measurement, exposed via PyO3 bindings.
2. Python orchestration — a Diff model and DiffEdit capability that use LLMs to generate search/replace operations from natural language requirements and apply them with configurable precision.

Key Components

Diff model

Represents a text transformation as a search / replace pair with optional line-range anchoring.

from fabricatio_diff.models.diff import Diff

# Pattern-matching diff
d = Diff(search="old text", replace="new text")
result = d.apply(source_text, match_precision=0.9)

# Anchor-based line-range diff (stable against content shifts)
d = Diff.from_anchors(start_anchor="10:a1b2", end_anchor="15:c3d4", replace="new lines")

# Line-number-based range diff
d = Diff.from_line_range(start=10, end=15, replace="new lines")

# Reverse a diff
rev = d.reverse()

# Format content with LINE:HASH anchors for LLM prompt context
hashed = d.format_with_hashes(source_text)

DiffEdit capability

Mixin class that delegates diff generation to an LLM via prompt templates. Parses the LLM response for <<<<SEARCH / <<<<REPLACE blocks and constructs a validated Diff.

from fabricatio_diff.capabilities.diff_edit import DiffEdit

class MyAgent(DiffEdit, SomeOtherCapability):
    pass

agent = MyAgent()
result = await agent.diff_edit(source_text, "rename variable x to count")

Rust Primitives (imported from fabricatio_diff.rust)

Function	Description
rate(a, b)	Normalized Damerau-Levenshtein similarity (0.0–1.0)
match_lines(haystack, needle, precision=0.9)	Find a fuzzy-matching block of lines
show_diff(a, b)	Generate a unified diff between two strings
compute_hash(line)	xxHash-based per-line hash
format_hashes(content, start_line=1)	Annotate each line with LINE:HASH
parse_hashline_anchor(anchor)	Parse "42:ab12" into (line, hash)
apply_set_line(content, anchor, new_text)	Replace one line by anchor
apply_insert_after(content, anchor, text)	Insert after an anchored line
apply_replace(content, old, new, all=False)	Simple text substitution
apply_replace_lines(content, start, end, text)	Replace a range between two anchors

Configuration

from fabricatio_diff.config import DiffConfig

# Match precision threshold (1.0 = exact, lower = fuzzier)
diff_config.match_precision = 0.85

# Prompt template for diff generation
diff_config.diff_template = "my/custom/template"

The DiffConfig dataclass is loaded from the global Fabricatio configuration system under the "diff" key.

Dependencies

• fabricatio-core — core interfaces, configuration system, and prompt template manager
• Rust crates: strsim (similarity), similar (unified diffs), rho-hashline (line hashing), rayon (parallel search)

License

MIT — see LICENSE