Merge commit '99665eb45f58d959d2cb9e49ddb960c79d596f33'

2 files changed, 69 insertions, 0 deletions

diff --git a/nixpkgs/doc/hooks/index.xml b/nixpkgs/doc/hooks/index.xml
new file mode 100644
index 000000000000..6a046eae2885
--- /dev/null
+++ b/nixpkgs/doc/hooks/index.xml
@@ -0,0 +1,10 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         xml:id="chap-hooks">
+ <title>Hooks reference</title>
+ <para>
+  Nixpkgs has several hook packages that augment the stdenv phases.
+ </para>
+ <xi:include href="./postgresql-test-hook.section.xml" />
+</chapter>
diff --git a/nixpkgs/doc/hooks/postgresql-test-hook.section.md b/nixpkgs/doc/hooks/postgresql-test-hook.section.md
new file mode 100644
index 000000000000..077fac14ebbf
--- /dev/null
+++ b/nixpkgs/doc/hooks/postgresql-test-hook.section.md
@@ -0,0 +1,59 @@
+
+# `postgresqlTestHook` {#sec-postgresqlTestHook}
+
+This hook starts a PostgreSQL server during the `checkPhase`. Example:
+
+```nix
+{ stdenv, postgresql, postgresqlTestHook }:
+stdenv.mkDerivation {
+
+  # ...
+
+  checkInputs = [
+    postgresql
+    postgresqlTestHook
+  ];
+}
+```
+
+If you use a custom `checkPhase`, remember to add the `runHook` calls:
+```nix
+  checkPhase ''
+    runHook preCheck
+
+    # ... your tests
+
+    runHook postCheck
+  ''
+```
+
+## Variables {#sec-postgresqlTestHook-variables}
+
+The hook logic will read a number of variables and set them to a default value if unset or empty.
+
+Exported variables:
+
+ - `PGDATA`: location of server files.
+ - `PGHOST`: location of UNIX domain socket directory; the default `host` in a connection string.
+ - `PGUSER`: user to create / log in with, default: `test_user`.
+ - `PGDATABASE`: database name, default: `test_db`.
+
+Bash-only variables:
+
+ - `postgresqlTestUserOptions`: SQL options to use when creating the `$PGUSER` role, default: `LOGIN`.
+ - `postgresqlTestSetupSQL`: SQL commands to run as database administrator after startup, default: statements that create `$PGUSER` and `$PGDATABASE`.
+ - `postgresqlTestSetupCommands`: bash commands to run after database start, defaults to running `$postgresqlTestSetupSQL` as database administrator.
+ - `postgresqlEnableTCP`: set to `1` to enable TCP listening. Flaky; not recommended.
+ - `postgresqlStartCommands`: defaults to `pg_ctl start`.
+
+## TCP and the Nix sandbox {#sec-postgresqlTestHook-tcp}
+
+`postgresqlEnableTCP` relies on network sandboxing, which is not available on macOS and some custom Nix installations, resulting in flaky tests.
+For this reason, it is disabled by default.
+
+The preferred solution is to make the test suite use a UNIX domain socket connection. This is the default behavior when no `host` connection parameter is provided.
+Some test suites hardcode a value for `host` though, so a patch may be required. If you can upstream the patch, you can make `host` default to the `PGHOST` environment variable when set. Otherwise, you can patch it locally to omit the `host` connection string parameter altogether.
+
+::: {.note}
+The error `libpq: failed (could not receive data from server: Connection refused` is generally an indication that the test suite is trying to connect through TCP.
+:::