Project Overview

PgTidy is a PostgreSQL-focused linter and formatter written in Go. It enforces a consistent SQL style, detects PostgreSQL-specific issues, and formats migrations, schemas, functions, procedures, triggers, and related database code. The primary day-one use case is formatting PL/pgSQL stored procedures to a defined house style.

It ships as a CLI, an LSP server, a VSCode extension, and (later) a DataGrip integration.

Agent Rules

Keep your answers short. Question everything, never assume or guess. Ask the user if you are unsure about anything.

Architecture

PgTidy uses a hybrid strategy:

Formatting is driven by a custom lossless lexer + CST (concrete syntax tree) that preserves every comment and whitespace span, so formatting can round-trip safely.
Linting (later milestones) is driven by the real PostgreSQL grammar via go-pgquery (libpg_query compiled to WASM with wazero — no cgo), which yields an accurate AST for deep semantic rules.

A single Go core backs every frontend (CLI, LSP, editors) and shares one diagnostics type.

cmd/pgtidy/        — CLI entry; subcommands: fmt, lint (v2), lsp (v3), version
pkg/lexer/         — lossless lexer: tokens + trivia (comments/whitespace) attached
pkg/cst/           — concrete syntax tree (round-trippable node model)
pkg/parser/        — recursive-descent parser → CST (DML + DDL + PL/pgSQL)
pkg/format/        — Doc-IR printer (Wadler/Prettier-style) + style application
pkg/config/        — .pgtidy.yaml discovery/merge: style + rule config
pkg/diagnostics/   — shared diagnostic type (CLI + LSP)
pkg/pgast/         — go-pgquery wrapper: SQL → real PG AST (lint, v2)
pkg/lint/          — rule engine + rule packs (v2)
pkg/lsp/           — LSP server (v3)
editors/vscode/    — VSCode extension (v3)
editors/datagrip/  — LSP4IJ integration (v4)
testdata/corpus/   — real-world .pgsql procedures used as the safety/idempotence harness

Why this architecture

No cgo (WASM-embedded libpg_query) keeps cross-compilation trivial and lets us bundle a single static binary per platform inside the VSCode extension.
Formatting needs a lossless CST — libpg_query drops comments and whitespace, so it cannot be the sole basis for a formatter. We build our own lexer/CST so the formatter never loses a comment.
Deep lint needs an accurate AST — go-pgquery gives the real PostgreSQL parse tree.
One core, many frontends — CLI, LSP, VSCode, and DataGrip all reuse the same engine and the same diagnostics type.

Core invariants (the formatter must never violate these)

Lossless lex: emit(lex(src)) == src byte-for-byte. The lexer keeps all trivia.
Semantic equivalence: formatting only changes trivia/layout. Verify by re-lexing the output and comparing the non-trivia token stream against the input.
Idempotence: fmt(fmt(x)) == fmt(x).
Graceful degradation: any span the parser cannot handle is passed through verbatim rather than corrupted.

Commands

go build ./cmd/pgtidy    # Build the binary
go test ./...            # Run all tests (incl. corpus safety harness)
go vet ./...             # Static analysis
go fmt ./...             # Format Go code

House style (formatter defaults; all configurable via .pgtidy.yaml)

Keywords UPPERCASE; data types lowercase; identifiers lowercase snake_case.
Indent: 2 spaces per level.
Leading-comma style, one item per line, for SELECT column lists and function params.
Function headers: params one-per-line in parens; LANGUAGE / SECURITY / volatility each on their own line; AS then $$ on its own line; body; closing $$; on its own line.
PL/pgSQL: DECLARE alone, vars 2-space indented; --Block-- comment markers preserved; BEGIN/END at body level; IF/ELSIF/ELSE/END IF, loops, CASE indent their bodies.
Spacing: spaces around binary operators (=, <>, ||, …) and :=; no space around ::, ->, ->>, array [...], or before a call's (.
Dollar-quote tags preserved verbatim ($$, $S$ , $Z$ , …).

Milestones

V1 — Formatter + CLI (current priority)

Lexer (pkg/lexer): full PG token coverage incl. dollar-quoted strings, -- and /* */ comments, operators. Comments + whitespace as leading/trailing trivia on tokens. Acceptance: emit(lex(src)) == src byte-for-byte across the corpus.
CST + parser (pkg/cst, pkg/parser): recursive descent for DML (SELECT/INSERT/ UPDATE/DELETE/CTE), DDL (CREATE FUNCTION/PROCEDURE/TABLE/INDEX/TRIGGER, ALTER, DO).
PL/pgSQL body parser: DECLARE/BEGIN/END, IF/CASE/LOOP, assignments, nested SQL.
Printer (pkg/format): Doc-IR (group/indent/line/softline) driven by style config. Graceful degradation — unparsed spans pass through verbatim.
CLI (cmd/pgtidy fmt): --check, --write/-w, stdin→stdout, --diff; config discovery walking up to .pgtidy.yaml; CI-friendly exit codes.
Config (pkg/config): load/merge style config; defaults = house style above.

V2 — Linter

pkg/pgast go-pgquery (WASM) wrapper; pkg/lint rule engine (rule ID, severity, config).
Rule packs: style/consistency, migration safety (ACCESS EXCLUSIVE locks, unsafe ALTER/ADD COLUMN, non-CONCURRENTLY index builds, blocking constraints), naming conventions, correctness/anti-patterns (SELECT *, missing WHERE on UPDATE/DELETE). Emit diagnostics.
pgtidy lint subcommand; --fix for autofixable rules.

V3 — LSP + VSCode

pkg/lsp: textDocument/formatting + range formatting, publishDiagnostics, codeAction quick-fixes — all reusing the core.
editors/vscode: TS extension using vscode-languageclient, launches bundled pgtidy lsp. Per-platform VSIX (win32/linux/darwin × x64/arm64) built in CI matrix.

V4 — DataGrip

editors/datagrip: integrate via LSP4IJ (free, works across JetBrains editions incl. DataGrip). No core changes expected.

Verification

Formatter: go test ./... runs golden-file tests + corpus harness asserting idempotence and token-stream equality before/after (no semantic change).
CLI: pgtidy fmt --check returns non-zero on unformatted input, zero when clean.
Lint (v2): fixture SQL with known violations → assert expected diagnostics; --fix round-trips.
LSP/VSCode (v3): load a .sql file in a dev-host VSCode, confirm format-on-save and live diagnostics via the bundled binary.

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