feat: support multiple versions of the pg_tap extension

[jfroche]

Build multiple versions of the pg_tap extension on different PostgreSQL versions.
Add test for the extensions and their upgrade on PostgreSQL 15 and 17.

Summary by CodeRabbit

• New Features

  • Added pgtap extension with multi-version packaging (1.2.0, 1.3.1, 1.3.3); per-version artifacts and metadata exposed and the latest version selected by default.
  • Added a package-level alias to install all pgtap versions and improved discoverability of per-version info.

• Tests

  • pgtap added to the extension test matrix to validate compatibility across supported PostgreSQL majors.

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[hunleyd]

rebase to fix conflicts?

[coderabbitai]

Walkthrough

Convert nix/ext/pgtap.nix from a single-derivation export to a buildEnv-driven multi-version factory that reads nix/ext/versions.json, produces per-version derivations with version-specific fetch/patch/install logic, exposes aggregated paths/pathsToLink and passthru metadata, and add pgtap to extension tests.

Changes

Cohort / File(s)	Summary
Multi-version pgtap build factory nix/ext/pgtap.nix	Replace top-level stdenv.mkDerivation with a buildEnv that reads versions.json, constructs per-version derivations (fetch, optional patch for 1.3.3, special-case 1.3.1 C extension), installs control/SQL/(.so) artifacts per Postgres version, and exposes paths, pathsToLink, and passthru (versions, numberOfVersions, pname-all, multi-version version). Adds buildEnv and fetchpatch2 inputs.
Extension version registry nix/ext/versions.json	Add pgtap entries: 1.2.0 (postgresql: ["15"], hash), 1.3.1 (postgresql: ["15","17"], hash), 1.3.3 (postgresql: ["15","17"], hash).
Test extension matrix nix/ext/tests/default.nix	Add pgtap to the public extension list used by tests (appears alongside other extension names such as postgis).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix(exts): handle pg_upgrade generated update_extensions.sql script in the extension tests #1896 — touches nix/ext/tests/default.nix and alters the public extension/test list similarly.
• feat(pg_repack): use default nixos extension test #1865 — also modifies the exported extension list in nix/ext/tests/default.nix.
• feat: test extensions with OrioleDB #1889 — adjusts the public extension test list in nix/ext/tests/default.nix.

Suggested reviewers

• samrose

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	The description is minimal and vague, lacking the required template structure with sections for motivation, changes, and testing details.	Complete the description by selecting and filling out the appropriate template (Default or Extension Upgrade) with detailed motivation, implementation changes, and testing information.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title clearly and concisely summarizes the main change: adding support for multiple versions of the pg_tap extension.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@nix/ext/pgtap.nix`:
- Around line 66-69: The sed invocation is using an undefined shell variable
`$ext`, so `module_pathname` will be wrong; fix by defining `ext` (e.g., set ext
to the correct shared-object path) before the sed call or replace `$ext` inline
with the correct path expression, and if the package may not build a C
extension, change the logic around `${pname}.control` generation (in the block
that runs sed and touches `${pname}--${version}.control`) to conditionally omit
the `module_pathname` line when `src/pgtap.so` (or the built shared object) does
not exist.

🧹 Nitpick comments (1)

nix/ext/pgtap.nix (1)

86-89: Hardcoded version check for C extension symlink.

The condition "${version}" == "1.3.1" is hardcoded. If a future pgtap version reintroduces a C extension, this logic won't automatically handle it. Consider documenting this decision or making the check more robust (e.g., based on whether the .so file exists and this is not the latest version).

♻️ Alternative approach

-        elif [[ "${version}" == "1.3.1" ]]; then
-          # 1.3.1 is the first and only version with a C extension
-          ln -sfn ${pname}-${version}${postgresql.dlSuffix} $out/lib/${pname}${postgresql.dlSuffix}
+        elif [[ -f src/pgtap.so && "${version}" != "${latestVersion}" ]]; then
+          # Create default symlink for non-latest versions with C extension
+          ln -sfn ${pname}-${version}${postgresql.dlSuffix} $out/lib/${pname}${postgresql.dlSuffix}
         fi

[coderabbitai]

Actionable comments posted: 2

🤖 Fix all issues with AI agents

In `@nix/ext/pgtap.nix`:
- Around line 9-29: Add a guard after computing supportedVersions/versions to
fail with a clear message when no matching entries exist: compute versions as
you do, then compute numberOfVersions (or use builtins.length versions) and use
lib.assert (or an explicit check) to ensure numberOfVersions > 0, failing with a
message that includes the current postgresql.version; this prevents lib.last
(latestVersion) from being called on an empty list and makes the error explicit.
- Around line 66-90: The control-file rewrite currently unconditionally replaces
module_pathname (using ext) which can point to a missing shared library for
SQL-only releases; change the logic so the sed rewrite that sets module_pathname
to $ext only runs when the shared library exists (the same test used for
src/pgtap${postgresql.dlSuffix}), and for SQL-only versions remove the
module_pathname line entirely (or leave it omitted) from the generated
${pname}--${version}.control so CREATE EXTENSION won't reference a non-existent
library.