nixpkgs/overlays/mods/update.sh

#!/usr/bin/env nix-shell
#!nix-shell --pure -i bash -p bash curl jq nix nix-prefetch cacert git
set -euo pipefail

# Update the n8n overlay (overlays/mods/n8n.nix) to the latest stable GitHub
# release of n8n-io/n8n.
#
# This is a self-contained updater (not nix-update), because the overlay file
# is a `prev.n8n.overrideAttrs` form rather than a standalone derivation and
# the test suite (tests/n8n-overlay-test.nix) explicitly forbids exporting a
# local n8n package. The CI workflow discovers and runs this script directly.
#
# What it does, in order:
#   1. Fetch latest stable (non-prerelease) tag from the GitHub API
#   2. Strip the `n8n@` prefix → version
#   3. Compare to the version pinned in overlays/mods/n8n.nix
#   4. Compute new src hash (fetchFromGitHub tarball) via nix-prefetch-url
#   5. Compute new pnpmDeps hash via the lib.fakeHash trick
#   6. Commit

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
NIX_FILE="$SCRIPT_DIR/n8n.nix"

REPO="n8n-io/n8n"
TAG_PREFIX="n8n@"

# ── 1. Latest stable release ───────────────────────────────────────────────
echo "Fetching latest stable release of $REPO ..."
LATEST_TAG=$(curl -fsSL "https://api.github.com/repos/$REPO/releases/latest" \
  | jq -r 'select(.prerelease == false) | .tag_name')

if [[ -z "$LATEST_TAG" ]]; then
  echo "ERROR: No stable release found for $REPO" >&2
  exit 1
fi

VERSION="${LATEST_TAG#${TAG_PREFIX}}"
echo "Latest version: $VERSION"

# ── 2. Current version from the nix file ───────────────────────────────────
CURRENT=$(awk '
  /^[[:space:]]*version = "/ {
    gsub(/^[[:space:]]*version = "/, "")
    gsub(/".*/, "")
    print
    exit
  }
' "$NIX_FILE")
echo "Current version: $CURRENT"

if [[ "$VERSION" == "$CURRENT" ]]; then
  echo "Already at latest version, nothing to do."
  exit 0
fi

echo "==> Updating n8n $CURRENT -> $VERSION"

# ── 3. Bump version in the file ────────────────────────────────────────────
sed -i "s|^\([[:space:]]*\)version = \"[^\"]*\";|\1version = \"$VERSION\";|" "$NIX_FILE"

# ── 4. Compute and apply src hash ──────────────────────────────────────────
echo "==> Computing src hash ..."
SRC_URL="https://github.com/$REPO/archive/refs/tags/${TAG_PREFIX}${VERSION}.tar.gz"
# `--name n8n-source` works around the `@` in the upstream tag name
# (nix-prefetch-url refuses filenames containing `@`).
SRC_HASH=$(nix-prefetch-url --unpack --type sha256 --name n8n-source "$SRC_URL" 2>/dev/null)
SRC_SRI=$(nix hash convert --hash-algo sha256 --to sri "$SRC_HASH")
echo "    src hash: $SRC_SRI"

# Replace the FIRST `hash = "sha256-...";` occurrence (the src block sits above pnpmDeps)
awk -v sri="$SRC_SRI" '
  !src_done && /^[[:space:]]*hash = "sha256-/ {
    sub(/"sha256-[A-Za-z0-9+/=]+"/, "\"" sri "\"")
    src_done = 1
  }
  { print }
' "$NIX_FILE" > "$NIX_FILE.tmp" && mv "$NIX_FILE.tmp" "$NIX_FILE"

# ── 5. Compute pnpmDeps hash via lib.fakeHash ──────────────────────────────
echo "==> Computing pnpmDeps hash (this may take a while) ..."

# 5a. Temporarily set the pnpmDeps hash to lib.fakeHash
awk '
  !pnpm_started && /^[[:space:]]*pnpmDeps = / { pnpm_started = 1 }
  pnpm_started && !pnpm_done && /^[[:space:]]*hash = "sha256-/ {
    sub(/"sha256-[A-Za-z0-9+/=]+"/, "lib.fakeHash")
    pnpm_done = 1
  }
  { print }
' "$NIX_FILE" > "$NIX_FILE.tmp" && mv "$NIX_FILE.tmp" "$NIX_FILE"

# 5b. Evaluate n8nModified.pnpmDeps — fixed-output derivation with a wrong hash
#     will fail and print the correct hash in the "got:" line.
SYSTEM=$(nix eval --impure --raw --expr 'builtins.currentSystem' 2>/dev/null || echo "x86_64-linux")
NIX_EXPR="(let
    flake = builtins.getFlake (toString ./.);
    pkgs = flake.inputs.nixpkgs.legacyPackages.\${builtins.currentSystem};
    n8nModified = import ./overlays/mods/n8n.nix { prev = pkgs; };
  in n8nModified.pnpmDeps)"

BUILD_OUTPUT=$(nix build --impure --no-link --expr "$NIX_EXPR" 2>&1 || true)

# Hash mismatch errors list two sha256 values: the wrong "Expected"/"specified"
# one (our lib.fakeHash = all A's) and the correct "Got"/"got" one. Different
# nix versions capitalise the label differently, so we filter out the fakeHash
# sentinel and take whatever real sha256 remains.
PNPM_HASH=$(echo "$BUILD_OUTPUT" \
  | grep -oE 'sha256-[A-Za-z0-9+/=]+' \
  | grep -v 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' \
  | tail -1)

if [[ -z "$PNPM_HASH" ]]; then
  echo "ERROR: Failed to compute pnpmDeps hash. nix build output:" >&2
  echo "$BUILD_OUTPUT" >&2
  echo "Restoring original file..." >&2
  git checkout -- "$NIX_FILE" 2>/dev/null || true
  exit 1
fi

echo "    pnpmDeps hash: $PNPM_HASH"

# 5d. Replace lib.fakeHash with the real hash
awk -v sri="$PNPM_HASH" '
  !pnpm_started && /^[[:space:]]*pnpmDeps = / { pnpm_started = 1 }
  pnpm_started && !pnpm_done && /^[[:space:]]*hash = / {
    sub(/lib\.fakeHash/, "\"" sri "\"")
    pnpm_done = 1
  }
  { print }
' "$NIX_FILE" > "$NIX_FILE.tmp" && mv "$NIX_FILE.tmp" "$NIX_FILE"

# ── 6. Verify the file parses and commit ───────────────────────────────────
echo "==> Verifying nix evaluation ..."
if ! nix eval --impure --expr "
  let
    flake = builtins.getFlake (toString ./.);
    pkgs = flake.inputs.nixpkgs.legacyPackages.\${builtins.currentSystem};
  in (import ./overlays/mods/n8n.nix { prev = pkgs; }).version
" >/dev/null 2>&1; then
  echo "ERROR: nix evaluation failed after update; restoring original." >&2
  git checkout -- "$NIX_FILE" 2>/dev/null || true
  exit 1
fi

NIXPKGS_ROOT=$(git -C "$SCRIPT_DIR" rev-parse --show-toplevel 2>/dev/null || true)
if [[ -n "$NIXPKGS_ROOT" ]] && \
   [[ -n "$(git -C "$NIXPKGS_ROOT" status --porcelain "$NIX_FILE")" ]]; then
  git -C "$NIXPKGS_ROOT" add "$NIX_FILE"
  git -C "$NIXPKGS_ROOT" commit -m "n8n: $CURRENT -> $VERSION"
  echo "==> Committed"
fi

echo "==> Done"