feat(gnomod): support parsing deprecated message (#773)

gnovm/pkg/gnomod/parse.go

@@ -99,8 +99,10 @@ func (f *File) add(errs *modfile.ErrorList, block *modfile.LineBlock, line *modf
 			errorf("repeated module statement")
 			return
 		}
+		deprecated := parseDeprecation(block, line)
 		f.Module = &modfile.Module{
-			Syntax: line,
+			Syntax:     line,
+			Deprecated: deprecated,
 		}
 		if len(args) != 1 {
 			errorf("usage: module module/path")

gnovm/pkg/gnomod/parse_test.go

@@ -0,0 +1,118 @@
+package gnomod
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestModuleDeprecated(t *testing.T) {
+	for _, tc := range []struct {
+		desc, in, expected string
+	}{
+		{
+			desc: "no_comment",
+			in:   `module m`,
+		},
+		{
+			desc: "other_comment",
+			in: `// yo
+			module m`,
+		},
+		{
+			desc: "deprecated_no_colon",
+			in: `//Deprecated
+			module m`,
+		},
+		{
+			desc: "deprecated_no_space",
+			in: `//Deprecated:blah
+			module m`,
+			expected: "blah",
+		},
+		{
+			desc: "deprecated_simple",
+			in: `// Deprecated: blah
+			module m`,
+			expected: "blah",
+		},
+		{
+			desc: "deprecated_lowercase",
+			in: `// deprecated: blah
+			module m`,
+		},
+		{
+			desc: "deprecated_multiline",
+			in: `// Deprecated: one
+			// two
+			module m`,
+			expected: "one\ntwo",
+		},
+		{
+			desc: "deprecated_mixed",
+			in: `// some other comment
+			// Deprecated: blah
+			module m`,
+		},
+		{
+			desc: "deprecated_middle",
+			in: `// module m is Deprecated: blah
+			module m`,
+		},
+		{
+			desc: "deprecated_multiple",
+			in: `// Deprecated: a
+			// Deprecated: b
+			module m`,
+			expected: "a\nDeprecated: b",
+		},
+		{
+			desc: "deprecated_paragraph",
+			in: `// Deprecated: a
+			// b
+			//
+			// c
+			module m`,
+			expected: "a\nb",
+		},
+		{
+			desc: "deprecated_paragraph_space",
+			in: `// Deprecated: the next line has a space
+			// 
+			// c
+			module m`,
+			expected: "the next line has a space",
+		},
+		{
+			desc:     "deprecated_suffix",
+			in:       `module m // Deprecated: blah`,
+			expected: "blah",
+		},
+		{
+			desc: `deprecated_mixed_suffix`,
+			in: `// some other comment
+			module m // Deprecated: blah`,
+		},
+		{
+			desc: "deprecated_mixed_suffix_paragraph",
+			in: `// some other comment
+			//
+			module m // Deprecated: blah`,
+			expected: "blah",
+		},
+		{
+			desc: "deprecated_block",
+			in: `// Deprecated: blah
+			module (
+				m
+			)`,
+			expected: "blah",
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			f, err := Parse("in", []byte(tc.in))
+			assert.Nil(t, err)
+			assert.Equal(t, tc.expected, f.Module.Deprecated)
+		})
+	}
+}

gnovm/pkg/gnomod/read.go

@@ -15,6 +15,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strconv"
 	"strings"
 	"unicode"
@@ -793,3 +794,42 @@ func parseReplace(filename string, line *modfile.Line, verb string, args []strin
 		Syntax: line,
 	}, nil
 }
+
+// parseDeprecation extracts the text of comments on a "module" directive and
+// extracts a deprecation message from that.
+//
+// A deprecation message is contained in a paragraph within a block of comments
+// that starts with "Deprecated:" (case sensitive). The message runs until the
+// end of the paragraph and does not include the "Deprecated:" prefix. If the
+// comment block has multiple paragraphs that start with "Deprecated:",
+// parseDeprecation returns the message from the first.
+func parseDeprecation(block *modfile.LineBlock, line *modfile.Line) string {
+	text := parseDirectiveComment(block, line)
+	rx := regexp.MustCompile(`(?s)(?:^|\n\n)Deprecated: *(.*?)(?:$|\n\n)`)
+	m := rx.FindStringSubmatch(text)
+	if m == nil {
+		return ""
+	}
+	return m[1]
+}
+
+// parseDirectiveComment extracts the text of comments on a directive.
+// If the directive's lien does not have comments and is part of a block that
+// does have comments, the block's comments are used.
+func parseDirectiveComment(block *modfile.LineBlock, line *modfile.Line) string {
+	comments := line.Comment()
+	if block != nil && len(comments.Before) == 0 && len(comments.Suffix) == 0 {
+		comments = block.Comment()
+	}
+	groups := [][]modfile.Comment{comments.Before, comments.Suffix}
+	var lines []string
+	for _, g := range groups {
+		for _, c := range g {
+			if !strings.HasPrefix(c.Token, "//") {
+				continue // blank line
+			}
+			lines = append(lines, strings.TrimSpace(strings.TrimPrefix(c.Token, "//")))
+		}
+	}
+	return strings.Join(lines, "\n")
+}