add support for using jackc/pgx as a driver (#122)

This patch updates `pggen` to support using `jackc/pgx` as
a database driver. `lib/pq` has entered maintenance mode, and
`jackc/pgx` is the recommended replacement. I still cannot
recommend using `jackc/pgx` as a driver at this time because it
has [a bug][1] that prevents `pggen` from gracefully handling
schema changes.

Most of the changes involve tweaking our scanners to be able
to consume both the data that `lib/pq` and `jackc/pgx` pass
down.

For the moment, the generated code still depends on `lib/pq`
because we need to be able to use `lib/pq.Array` to scan arrays
of values. Once `jackc/pgx` becomes the recommended driver, we
will switch to using whatever the equivalent of `lib/pq.Array`
is for `jackc/pgx` (or roll our own). We will not drop support
for using `lib/pq` as a driver (likely not ever, but certainly
not without a major version bump).

This bumps our go versions, including the msgv. We need to bump
the msgv because jackc/pgx does not support go 1.11.

Closes #119

[1]: jackc/pgx#841

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.14-alpine
+FROM golang:1.15-alpine
 
 # we need postgresql-client so we can set up our database with psql
 # for testing and `go` uses `git` to fetch deps for us. musl-dev

Dockerfile.msgv

@@ -2,7 +2,7 @@
 # This docker file is for running tests against the earliest support go
 # version.
 #
-FROM golang:1.11-alpine
+FROM golang:1.13-alpine
 
 # we need postgresql-client so we can set up our database with psql
 # for testing and `go` uses `git` to fetch deps for us. musl-dev

HACKING.md

@@ -114,6 +114,22 @@ CI checks a bit, but hopefully this is made up for by the fact that the `docker-
 file in the repo root makes debugging CI jobs easier. We maintain two different compose files
 so that we can share the source between the host and the container during local development.
 
+## Testing Non-Default Drivers
+
+`pggen` supports using both `github.com/lib/pq` and `github.com/jackc/pgx/stdlib` as
+database drivers. For the moment `lib/pq` is recommended because `jackc/pgx` contains
+a [nasty bug](https://github.com/jackc/pgx/issues/841) that prevents our test suite
+from passing fully. Going forward we do want to switch to recommending `jackc/pgx`,
+as it is more actively maintained than `lib/pq`.
+
+The example tests all use the recommended driver (`lib/pq`) for testing to keep the example code
+simple. The main test suite `cmd/pggen/test` is parameterized over the driver though. It
+allows you to you set the driver name via the `DB_DRIVER` environment variable. You can
+either set this variable to `postgres` (to use `lib/pq`) or `pgx` (to use
+`github.com/jackc/pgx/stdlib`).
+
+The `tools/test.bash` script runs the test suite both ways.
+
 # Philosophy
 
 Certain aspects of the style in which `pggen` is developed are intentionally divergent

cmd/pggen/test/overrides_test.go

@@ -17,7 +17,8 @@ func TestOverriddenGetTimes(t *testing.T) {
 	res, err := overriddenPgClient.GetTimes(ctx)
 	chkErr(t, err)
 
-	if res[0].TsFieldNotNull.String() != "1999-01-08 04:05:06 +0000 +0000" {
+	tsStr := res[0].TsFieldNotNull.String()
+	if !(tsStr == "1999-01-08 04:05:06 +0000 +0000" || tsStr == "1999-01-08 04:05:06 +0000 UTC") {
 		t.Fatalf("bad ts field: '%s'", res[0].TsFieldNotNull.String())
 	}
 

cmd/pggen/test/prepared_function_test.go

@@ -2,6 +2,7 @@ package test
 
 import (
 	"encoding/json"
+	"math"
 	"reflect"
 	"regexp"
 	"testing"
@@ -96,18 +97,21 @@ func TestSelectTime(t *testing.T) {
 	chkErr(t, err)
 
 	ti := times[0]
-	if ti.TsField.String() != "1999-01-08 04:05:06 +0000 +0000" {
+	timeStr := ti.TsField.String()
+	if !(timeStr == "1999-01-08 04:05:06 +0000 +0000" || timeStr == "1999-01-08 04:05:06 +0000 UTC") {
 		t.Fatalf("0: tsfield (actual = '%s')", ti.TsField.String())
 	}
-	if ti.TsFieldNotNull.String() != "1999-01-08 04:05:06 +0000 +0000" {
+	timeStr = ti.TsFieldNotNull.String()
+	if !(timeStr == "1999-01-08 04:05:06 +0000 +0000" || timeStr == "1999-01-08 04:05:06 +0000 UTC") {
 		t.Fatalf("0: tsfieldnn (actual = '%s'", ti.TsFieldNotNull.String())
 	}
 
 	ti = times[1]
 	if ti.TsField != nil {
 		t.Fatalf("1: tsfield unexpectedly valid")
 	}
-	if ti.TsFieldNotNull.String() != "1999-01-08 04:05:06 +0000 +0000" {
+	timeStr = ti.TsFieldNotNull.String()
+	if !(timeStr == "1999-01-08 04:05:06 +0000 +0000" || timeStr == "1999-01-08 04:05:06 +0000 UTC") {
 		t.Fatalf("1: tsfieldnn (actual = '%s')", ti.TsFieldNotNull.String())
 	}
 	// TODO: there is something weird going on with time marshalling. It
@@ -190,14 +194,14 @@ func TestSelectNumbers(t *testing.T) {
 			t.Fatalf("%d: numeric prec scale mismatch", i)
 		}
 
-		if (i == 0 && !reflect.DeepEqual(n.RealField, &n2d3)) ||
-			!reflect.DeepEqual(n.RealFieldNotNull, &n2d3) {
+		if (i == 0 && math.Abs(*n.RealField-n2d3) > 0.001) ||
+			math.Abs(*n.RealFieldNotNull-n2d3) > 0.001 {
 			t.Fatalf("%d: real mismatch", i)
 		}
 
 		if (i == 0 && !reflect.DeepEqual(n.DoubleField, &n9d3)) ||
 			!reflect.DeepEqual(n.DoubleFieldNotNull, &n9d3) {
-			t.Fatalf("%d: real mismatch", i)
+			t.Fatalf("%d: double mismatch", i)
 		}
 	}
 }

cmd/pggen/test/tables_test.go

@@ -2,6 +2,7 @@ package test
 
 import (
 	"database/sql"
+	"os"
 	"reflect"
 	"sort"
 	"testing"
@@ -1118,6 +1119,12 @@ func TestNotFoundList(t *testing.T) {
 }
 
 func TestDroppingColumnOnTheFly(t *testing.T) {
+	if os.Getenv("DB_DRIVER") == "pgx" {
+		// disable this test for jackc/pgx
+		// TODO: re-enable once https://github.com/jackc/pgx/issues/841 is resolved
+		return
+	}
+
 	// make sure we always start in a consistant state
 	_, err := pgClient.Handle().ExecContext(ctx, `
 		DROP TABLE drop_cols;
@@ -1144,6 +1151,8 @@ func TestDroppingColumnOnTheFly(t *testing.T) {
 
 	// load the record again
 	dc, err := pgClient.GetDropCol(ctx, id)
+	// NOTE: error actually occurs in github.com/jackc/pgx/v4/stdlib.(*Conn).QueryContex
+	//       when scanning the very first row.
 	chkErr(t, err)
 
 	if dc.F1 != 0 {
@@ -1154,7 +1163,7 @@ func TestDroppingColumnOnTheFly(t *testing.T) {
 		t.Fatalf("expected F2 to be 2, was %d", dc.F2)
 	}
 
-	// pull the rug out from under us
+	// replace the old column
 	_, err = pgClient.Handle().ExecContext(ctx, `ALTER TABLE drop_cols ADD COLUMN f1 int NOT NULL DEFAULT 1`)
 	chkErr(t, err)
 }

cmd/pggen/test/test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"database/sql"
 	"encoding/json"
+	_ "github.com/jackc/pgx/v4/stdlib" // load driver
 	"log"
 	"os"
 	"os/exec"
@@ -31,7 +32,12 @@ func init() {
 		log.Fatalf("no DB_URL in the environment")
 	}
 
-	db, err := sql.Open("postgres", dbURL)
+	dbDriver, inEnv := os.LookupEnv("DB_DRIVER")
+	if !inEnv || dbDriver == "" {
+		dbDriver = "postgres" // default to using lib/pq
+	}
+
+	db, err := sql.Open(dbDriver, dbURL)
 	if err != nil {
 		log.Fatal(err)
 	}