hashicorp · radeksimko · Apr 24, 2020
@@ -0,0 +1,54 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/hashicorp/go-changelog/parser"
+)
+
+func main() {
+	wd, err := os.Getwd()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+
+	var changelogPath string
+	flag.StringVar(&changelogPath, "path", filepath.Join(wd, "CHANGELOG.md"), "path to the changelog file")
+
+	// extractVersion represents version to extract changelog for (e.g. 1.0.0)
+	extractVersion := flag.Arg(0)
+	flag.Parse()
+
+	if extractVersion == "" {
+		fmt.Fprintf(os.Stderr, "Must specify version\n\n")
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	f, err := os.Open(changelogPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to open file: %s", err)
+		os.Exit(1)
+	}
+
+	sp, err := parser.NewSectionParser(f)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "unable to read changelog file: %s", err)
+		os.Exit(1)
+	}
+	s, err := sp.Section(extractVersion)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err.Error())
+		os.Exit(1)
+	}
+
+	_, err = os.Stdout.Write(s.Body)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err.Error())
+		os.Exit(1)
+	}
+}
@@ -5,6 +5,7 @@ go 1.16
 require (
 	github.com/go-git/go-billy/v5 v5.3.1
 	github.com/go-git/go-git/v5 v5.4.2
+	github.com/google/go-cmp v0.3.0
 	github.com/google/go-github v17.0.0+incompatible
 	github.com/google/go-querystring v1.0.0 // indirect
 	github.com/manifoldco/promptui v0.8.0

@@ -0,0 +1,19 @@
+package parser
+
+import "fmt"
+
+type VersionNotFoundErr struct {
+	Version string
+}
+
+func (e *VersionNotFoundErr) Is(target error) bool {
+	tErr, ok := target.(*VersionNotFoundErr)
+	if !ok {
+		return false
+	}
+	return tErr.Version == e.Version
+}
+
+func (e *VersionNotFoundErr) Error() string {
+	return fmt.Sprintf("version %s not found", e.Version)
+}
@@ -0,0 +1,122 @@
+package parser
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"regexp"
+)
+
+var (
+	defaultSectionReFmt = `(?s)(?P<header>## %s[^\n]*)
+(?P<body>.+?)
+(?:## .+|$)`
+	headerMatchName = "header"
+	bodyMatchName   = "body"
+)
+
+type SectionParser struct {
+	RegexpFormat string
+	content      []byte
+}
+
+func NewSectionParser(r io.Reader) (*SectionParser, error) {
+	b, err := io.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+
+	return &SectionParser{
+		RegexpFormat: defaultSectionReFmt,
+		content:      b,
+	}, nil
+}
+
+type SectionRange struct {
+	HeaderRange *ByteRange
+	BodyRange   *ByteRange
+}
+
+type ByteRange struct {
+	From, To int
+}
+
+func (p *SectionParser) regexpFormat() string {
+	if p.RegexpFormat == "" {
+		return defaultSectionReFmt
+	}
+	return p.RegexpFormat
+}
+
+func (p *SectionParser) regexp(v string) (*regexp.Regexp, error) {
+	escapedVersion := regexp.QuoteMeta(v)
+	return regexp.Compile(fmt.Sprintf(p.regexpFormat(), escapedVersion))
+}
+
+func (p *SectionParser) SectionRange(v string) (*SectionRange, error) {
+	re, err := p.regexp(v)
+	if err != nil {
+		return nil, err
+	}
+
+	loc := re.FindSubmatchIndex(p.content)
+	if loc == nil {
+		return nil, &VersionNotFoundErr{v}
+	}
+
+	headerIdx, err := findSubexpIndexes(re, headerMatchName)
+	if err != nil {
+		return nil, err
+	}
+
+	bodyIdx, err := findSubexpIndexes(re, bodyMatchName)
+	if err != nil {
+		return nil, err
+	}
+
+	return &SectionRange{
+		HeaderRange: &ByteRange{
+			From: loc[headerIdx.from],
+			To:   loc[headerIdx.to],
+		},
+		BodyRange: &ByteRange{
+			From: loc[bodyIdx.from],
+			To:   loc[bodyIdx.to],
+		},
+	}, nil
+}
+
+type index struct {
+	from, to int
+}
+
+func findSubexpIndexes(re *regexp.Regexp, name string) (*index, error) {
+	for i, seName := range re.SubexpNames() {
+		if seName == name {
+			from := i * 2
+			return &index{from, from + 1}, nil
+		}
+	}
+
+	return nil, fmt.Errorf("subexpression %q not found", name)
+}
+
+type Section struct {
+	Header []byte
+	Body   []byte
+}
+
+func (p *SectionParser) Section(v string) (*Section, error) {
+	sr, err := p.SectionRange(v)
+	if err != nil {
+		return nil, err
+	}
+
+	headerRng := sr.HeaderRange
+	bodyRng := sr.BodyRange
+
+	return &Section{
+		Header: bytes.TrimSpace(p.content[headerRng.From:headerRng.To]),
+		Body:   bytes.TrimSpace(p.content[bodyRng.From:bodyRng.To]),
+	}, nil
+}
@@ -0,0 +1,101 @@
+package parser
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestParser_Section(t *testing.T) {
+	testCases := []struct {
+		name    string
+		content string
+		version string
+
+		expectedSection *Section
+		expectedErr     error
+	}{
+		{
+			"empty log",
+			"",
+			"0.12.0",
+			nil,
+			&VersionNotFoundErr{"0.12.0"},
+		},
+		{
+			"version not found",
+			`## 0.11.0
+
+something
+
+## 0.10.0
+
+testing
+`,
+			"0.12.0",
+			nil,
+			&VersionNotFoundErr{"0.12.0"},
+		},
+		{
+			"matching unreleased version",
+			`## 0.12.0 (Unreleased)
+
+something
+
+## 0.11.0
+
+testing
+`,
+			"0.12.0",
+			&Section{
+				Header: []byte("## 0.12.0 (Unreleased)"),
+				Body:   []byte("something"),
+			},
+			nil,
+		},
+		{
+			"matching released version - top",
+			`## 0.12.0
+matching text
+with newline
+
+## 0.11.99
+
+ - something
+ - else
+`,
+			"0.12.0",
+			&Section{
+				Header: []byte("## 0.12.0"),
+				Body: []byte(`matching text
+with newline`),
+			},
+			nil,
+		},
+	}
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("%d-%s", i, tc.name), func(t *testing.T) {
+			r := strings.NewReader(tc.content)
+			p, err := NewSectionParser(r)
+			if err != nil {
+				t.Fatal(err)
+			}
+			s, err := p.Section(tc.version)
+			if err == nil && tc.expectedErr != nil {
+				t.Fatalf("expected error: %s", tc.expectedErr.Error())
+			}
+
+			if !errors.Is(err, tc.expectedErr) {
+				diff := cmp.Diff(tc.expectedErr, err)
+				t.Fatalf("error doesn't match: %s", diff)
+			}
+
+			if diff := cmp.Diff(tc.expectedSection, s); diff != "" {
+				t.Fatalf("parsed section don't match: %s", diff)
+			}
+		})
+	}
+}