Create command 'tmpl-expand', for document production

Command-line utility:  Builds a Key=Value map and passes it
to 'template.Execute()' for read of template source from stdin.

Author: dmullis

cmd/tmpl-expand/main.go

@@ -0,0 +1,277 @@
+// Copyright 2022 Donald Mullis. All rights reserved.
+
+// See `tmpl-expand -help` for abstract.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"path"
+	"regexp"
+	"sort"
+	"strings"
+	"text/template"
+)
+
+type (
+	KvpArg struct {
+		Key    string
+		Value string
+	}
+	TemplateContext struct {
+		//    https://golang.org/pkg/text/template/#hdr-Arguments
+		tmpl *template.Template
+		substitutionsMap map[string]string
+	}
+)
+
+// General args
+var (
+	writeMarkdown = flag.Bool("markdown", false,
+		`Write out usage doc in Github-flavored Markdown format`)
+
+	exitStatus int
+)
+
+func init() {
+	log.SetFlags(log.Lshortfile)
+}
+
+func main() {
+	flag.Usage = func() {
+		UsageDump()
+		os.Exit(1)
+	}
+	flag.Parse()
+	if !flag.Parsed() {
+		log.Fatalln("flag.Parsed() == false")
+	}
+
+	if *writeMarkdown {
+		UsageMarkdown()
+		return
+	}
+
+	kvpArgs, defFileNameArgs := scanForKVArgs(flag.Args())
+	for _, filename := range defFileNameArgs {
+		kvpArg := scanValueFile(filename)
+		kvpArgs[kvpArg.Key] = kvpArg.Value
+
+	}
+	templateText := getTemplate(os.Stdin)
+	ExpandTemplate(kvpArgs, templateText)
+	os.Exit(exitStatus)
+}
+
+var usageAbstract = `
+  Key=Value
+   Sh-style name=value definition string pairs.  The Key name must be
+   valid as a Go map Key acceptable to Go's template
+   package https://pkg.go.dev/text/template
+
+  ValueFilePath
+   File named on the command line containing a possibly multi-line
+   definition of a single 'Value', with its 'Key' derived from the base name of the file.
+   All non-alphanumeric characters in the basename are mapped to "_", to ensure their acceptability as
+   Go template keys.
+
+  TemplateFile
+   A stream read from stdin format template containing references to
+   the 'Key' side of the above pairs.
+
+  ExpansionFile
+   Written to stdout, the expansion of the input template read from stdin.
+
+---
+Example:
+
+        echo >/tmp/valueFile.txt '
+      .      +-------+
+      .      | a box |
+      .      +-------+'
+        echo '
+      .     A sentence referencing Key 'boxShape' with Value '{{.boxShape}}', read
+      .     from the command line. 
+      .
+      .     An introductory clause followed by a multi-line block of text,
+      .     read from a file:
+      .       {{.valueFile}}' |
+        tmpl-expand boxShape='RECTANGULAR' /tmp/valueFile.txt
+
+Result:
+      .     A sentence referencing Key boxShape with Value RECTANGULAR, read
+      .     from the command line. 
+      .
+      .     An introductory clause followed by a multi-line block of text,
+      .     read from a file:
+      .       
+      .      +-------+
+      .      | a box |
+      .      +-------+
+`
+
+func writeUsage(out io.Writer, premable string) {
+	fmt.Fprintf(out, "%s%s", premable,
+  `Usage:
+        tmpl-expand [-markdown] [ Key=Value | ValueFilePath ] ... <TemplateFile >ExpansionFile
+`)
+	flag.PrintDefaults()
+	fmt.Fprintf(out, "%s\n", usageAbstract)
+}
+
+func UsageDump() {
+	writeUsage(os.Stderr, "")
+}
+
+func scanForKVArgs(args []string) (
+	kvpArgs map[string]string, filenameArgs []string) {
+	kvpArgs = make(map[string]string)
+	for _, arg := range args {
+		kvp := strings.Split(arg, "=")
+		if len(kvp) != 2 {
+			filenameArgs = append(filenameArgs, kvp[0])
+			continue
+		}
+		newKvpArg := newKVPair(kvp)
+
+		// Search earlier Keys for duplicates.
+		//   XX  N^2 in number of Keys -- use a map instead?
+		for k := range kvpArgs {
+			if k == newKvpArg.Key {
+				log.Printf("Duplicate key specified: '%v', '%v'", kvp, newKvpArg)
+				exitStatus = 1
+			}
+		}
+		kvpArgs[newKvpArg.Key] = newKvpArg.Value
+	}
+	return
+}
+
+func newKVPair(newKvp []string) KvpArg {
+	vetKVstring(newKvp)
+	return KvpArg{
+		Key:   newKvp[0],
+		Value: newKvp[1],
+	}
+}
+
+func vetKVstring(kv []string) {
+	reportFatal := func(format string) {
+		// X X   Caller disappears from stack, apparently due to inlining, despite
+		//       disabling Go optimizer
+		//caller := func(howHigh int) string {
+		//	pc, file, line, ok := runtime.Caller(howHigh)
+		//	_ = pc
+		//	if !ok {
+		//		return ""
+		//	}
+		//	baseFileName := file[strings.LastIndex(file, "/")+1:]
+		//	return baseFileName + ":" + strconv.Itoa(line)
+		//}
+		log.Printf(format, kv)
+		log.Fatalln("FATAL")
+	}
+	if len(kv[0]) <= 0 {
+		reportFatal("Key side of Key=Value pair empty: %#v\n")
+	}
+	if len(kv[1]) <= 0 {
+		reportFatal("Value side of Key=Value pair empty: %#v\n")
+	}
+}
+
+var alnumOnlyRE = regexp.MustCompile(`[^a-zA-Z0-9]`)
+
+func scanValueFile(keyPath string) KvpArg {
+	valueFile, err := os.Open(keyPath)
+	if err != nil {
+		log.Fatalln(err)
+	}
+	bytes, err := io.ReadAll(valueFile)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	basename := path.Base(keyPath)
+	return KvpArg{
+		Key:   alnumOnlyRE.ReplaceAllLiteralString(basename, "_"),
+		Value: string(bytes),
+	}
+}
+
+//func getTemplate(infile *os.File) (int, string) {
+func getTemplate(infile *os.File) string {
+	var err error
+	var stat os.FileInfo
+	stat, err = infile.Stat()
+	if err != nil {
+		log.Fatalln(err)
+	}
+	templateText := make([]byte, stat.Size())
+	var nRead int
+	templateText, err = io.ReadAll(infile)
+	nRead = len(templateText)
+	if nRead <= 0 {
+		log.Fatalf("os.Read returned %d bytes", nRead)
+	}
+	if err = infile.Close(); err != nil {
+		log.Fatalf("Could not close %v, err=%v", infile, err)
+	}
+	return string(templateText)
+}
+
+func ExpandTemplate(kvpArgs map[string]string, templateText string) {
+
+	ctx := TemplateContext{
+		substitutionsMap: kvpArgs,
+	}
+
+	var err error
+	ctx.tmpl, err = template.New("" /*baseFile*/).Option("missingkey=error").
+		Parse(templateText)
+	if err != nil {
+		log.Printf("Failed to parse '%s'", templateText)
+		log.Fatalln(err)
+	}
+	ctx.writeFile()
+}
+
+func (ctx *TemplateContext) writeFile() {
+	if err := ctx.tmpl.Execute(os.Stdout, ctx.substitutionsMap); err != nil {
+		fmt.Fprintf(os.Stderr, "Template.Execute(outfile, map) returned  err=\n   %v\n",
+			err)
+		fmt.Fprintf(os.Stderr, "Contents of failing map:\n%s", ctx.formatMap())
+		exitStatus = 1
+	}
+	if err := os.Stdout.Close(); err != nil {
+		log.Fatal(err)
+	}
+	return
+}
+
+// Sort the output, for deterministic comparisons of build failures.
+func (ctx *TemplateContext) formatMap() (out string) {
+	alphaSortMap(ctx.substitutionsMap,
+		func(s string) {
+			v := ctx.substitutionsMap[s]
+			const TRIM = 80
+			if len(v) > TRIM {
+				v = v[:TRIM] + "..."
+			}
+			out += fmt.Sprintf("   % 20s '%v'\n\n", s, v)
+		})
+	return
+}
+
+func alphaSortMap(m map[string]string, next func(s string)) {
+	var h sort.StringSlice
+	for k, _ := range m {
+		h = append(h, k)
+	}
+	h.Sort()
+	for _, s := range h {
+		next(s)
+	}
+}

cmd/tmpl-expand/make.sh

@@ -0,0 +1,14 @@
+#! /bin/sh
+
+set -e
+build_variant=build
+if [ "$1" ]
+then
+    build_variant="$1"
+    shift
+fi
+
+go ${build_variant}
+go run . --markdown >README.md
+marked -gfm README.md >README.html
+

cmd/tmpl-expand/markdown.go

@@ -0,0 +1,46 @@
+// Copyright 2022 Donald Mullis. All rights reserved.
+
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+func UsageMarkdown() {
+	var bytes strings.Builder
+	flag.CommandLine.SetOutput(&bytes)
+
+	writeUsage(&bytes, `<!-- Automatically generated Markdown, do not edit -->
+ <style type="text/css">
+ h3 {margin-block-end: -0.5em;}
+ h4 {margin-block-end: -0.5em;}
+ code {font-size: larger;}
+ </style>
+`)
+	indentedTextToMarkdown(bytes)
+}
+
+var column1Regex = regexp.MustCompile(`^[A-Z]`)
+const column1AtxHeading = "  ### "
+
+var column3Regex = regexp.MustCompile(`^  [^ ]`)
+const column3AtxHeading = "  #### "
+// https://github.github.com/gfm/#atx-headings
+
+// writes to stdout
+func indentedTextToMarkdown(bytes strings.Builder) {
+	scanner := bufio.NewScanner(strings.NewReader(bytes.String()))
+	for scanner.Scan() {
+		line := scanner.Text()
+		if column1Regex.MatchString(line) {
+			line = column1AtxHeading + line
+		} else if column3Regex.MatchString(line) {
+			line = column3AtxHeading + line
+		}
+		fmt.Println(line)
+	}
+}