Extract a library from the confix command-line tool. (#9012) (#9024)

(cherry picked from commit 18b5a500da)

Pull out the library functionality from scripts/confix and move it to
internal/libs/confix. Replace scripts/confix with a simple stub that has the
same command-line API, but uses the library instead.

Related:

- Move and update unit tests.
- Move scripts/confix/condiff to scripts/condiff.
- Update test data for v34, v35, and v36.
- Update reference diffs.
- Update testdata README.

Co-authored-by: M. J. Fromberger <fromberger@interchain.io>

scripts/condiff/condiff.go

@@ -0,0 +1,152 @@
+// Program condiff performs a keyspace diff on two TOML documents.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+
+	"github.com/creachadair/tomledit"
+	"github.com/creachadair/tomledit/parser"
+	"github.com/creachadair/tomledit/transform"
+)
+
+var (
+	doDesnake = flag.Bool("desnake", false, "Convert snake_case to kebab-case before comparing")
+)
+
+func init() {
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, `Usage: %[1]s [options] f1 f2
+
+Diff the keyspaces of the TOML documents in files f1 and f2.
+The output prints one line per key that differs:
+
+   -S name    -- section exists in f1 but not f2
+   +S name    -- section exists in f2 but not f1
+   -M name    -- mapping exists in f1 but not f2
+   +M name    -- mapping exists in f2 but not f1
+
+Comments, order, and values are ignored for comparison purposes.
+
+Options:
+`, filepath.Base(os.Args[0]))
+		flag.PrintDefaults()
+	}
+}
+
+func main() {
+	flag.Parse()
+
+	if flag.NArg() != 2 {
+		log.Fatalf("Usage: %[1]s <lhs> <rhs>", filepath.Base(os.Args[0]))
+	}
+	lhs := mustParse(flag.Arg(0))
+	rhs := mustParse(flag.Arg(1))
+	if *doDesnake {
+		log.Printf("Converting all names from snake_case to kebab-case")
+		fix := transform.SnakeToKebab()
+		_ = fix(context.Background(), lhs)
+		_ = fix(context.Background(), rhs)
+	}
+	diffDocs(os.Stdout, lhs, rhs)
+}
+
+func mustParse(path string) *tomledit.Document {
+	f, err := os.Open(path)
+	if err != nil {
+		log.Fatalf("Opening TOML input: %v", err)
+	}
+	defer f.Close()
+	doc, err := tomledit.Parse(f)
+	if err != nil {
+		log.Fatalf("Parsing %q: %v", path, err)
+	}
+	return doc
+}
+
+func allKeys(s *tomledit.Section) []string {
+	var keys []string
+	s.Scan(func(key parser.Key, _ *tomledit.Entry) bool {
+		keys = append(keys, key.String())
+		return true
+	})
+	return keys
+}
+
+const (
+	delSection = "-S"
+	delMapping = "-M"
+	addSection = "+S"
+	addMapping = "+M"
+
+	delMapSep = "\n" + delMapping + " "
+	addMapSep = "\n" + addMapping + " "
+)
+
+func diffDocs(w io.Writer, lhs, rhs *tomledit.Document) {
+	diffSections(w, lhs.Global, rhs.Global)
+	lsec, rsec := lhs.Sections, rhs.Sections
+	transform.SortSectionsByName(lsec)
+	transform.SortSectionsByName(rsec)
+
+	i, j := 0, 0
+	for i < len(lsec) && j < len(rsec) {
+		if lsec[i].Name.Before(rsec[j].Name) {
+			fmt.Fprintln(w, delSection, lsec[i].Name)
+			fmt.Fprintln(w, delMapping, strings.Join(allKeys(lsec[i]), delMapSep))
+			i++
+		} else if rsec[j].Name.Before(lsec[i].Name) {
+			fmt.Fprintln(w, addSection, rsec[j].Name)
+			fmt.Fprintln(w, addMapping, strings.Join(allKeys(rsec[j]), addMapSep))
+			j++
+		} else {
+			diffSections(w, lsec[i], rsec[j])
+			i++
+			j++
+		}
+	}
+	for ; i < len(lsec); i++ {
+		fmt.Fprintln(w, delSection, lsec[i].Name)
+		fmt.Fprintln(w, delMapping, strings.Join(allKeys(lsec[i]), delMapSep))
+	}
+	for ; j < len(rsec); j++ {
+		fmt.Fprintln(w, addSection, rsec[j].Name)
+		fmt.Fprintln(w, addMapping, strings.Join(allKeys(rsec[j]), addMapSep))
+	}
+}
+
+func diffSections(w io.Writer, lhs, rhs *tomledit.Section) {
+	diffKeys(w, allKeys(lhs), allKeys(rhs))
+}
+
+func diffKeys(w io.Writer, lhs, rhs []string) {
+	sort.Strings(lhs)
+	sort.Strings(rhs)
+
+	i, j := 0, 0
+	for i < len(lhs) && j < len(rhs) {
+		if lhs[i] < rhs[j] {
+			fmt.Fprintln(w, delMapping, lhs[i])
+			i++
+		} else if lhs[i] > rhs[j] {
+			fmt.Fprintln(w, addMapping, rhs[j])
+			j++
+		} else {
+			i++
+			j++
+		}
+	}
+	for ; i < len(lhs); i++ {
+		fmt.Fprintln(w, delMapping, lhs[i])
+	}
+	for ; j < len(rhs); j++ {
+		fmt.Fprintln(w, addMapping, rhs[j])
+	}
+}