feat: implement diff parser (#16)

.stylist.yml

@@ -2,4 +2,8 @@ processors:
   - preset: cspell
   - preset: gitleaks
   - preset: golangci-lint
+  - preset: gofmt
   - preset: markdownlint
+  # - preset: hadolint
+  # - preset: shellcheck
+  # - preset: shfmt

go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/imdario/mergo v0.3.13
 	github.com/owenrumney/go-sarif v1.1.1
 	github.com/sirupsen/logrus v1.9.0
+	github.com/sourcegraph/go-diff v0.7.0
 	github.com/spf13/cobra v1.6.1
 	github.com/spf13/pflag v1.0.5
 	github.com/stretchr/testify v1.8.1

go.sum

@@ -40,6 +40,7 @@ github.com/go-playground/validator/v10 v10.11.1/go.mod h1:i+3WkQ1FvaUjjxh1kSvIA4
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.4/go.mod h1:vzj43D7+SQXF/4pzW/hwtAqwc6iTitCiVSaWz5lYuqw=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
+github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.7 h1:81/ik6ipDQS2aGcBfIN5dHDB36BwrStyeAQquSYCV4o=
 github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 h1:El6M4kTTCOh6aBiKaUGG7oYTSPP8MxqL4YI3kZKwcP4=
 github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510/go.mod h1:pupxD2MaaD3pAXIBCelhxNneeOaAeabZDe5s4K6zSpQ=
@@ -101,8 +102,12 @@ github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQD
 github.com/shopspring/decimal v1.2.0/go.mod h1:DKyhrW/HYNuLGql+MJL6WCR6knT2jwCFRcu2hWCYk4o=
 github.com/shopspring/decimal v1.3.1 h1:2Usl1nmF/WZucqkFZhnfFYxxxu8LG21F6nPQBE5gKV8=
 github.com/shopspring/decimal v1.3.1/go.mod h1:DKyhrW/HYNuLGql+MJL6WCR6knT2jwCFRcu2hWCYk4o=
+github.com/shurcooL/go v0.0.0-20180423040247-9e1955d9fb6e/go.mod h1:TDJrrUr11Vxrven61rcy3hJMUqaf/CLWYhHNPmT14Lk=
+github.com/shurcooL/go-goon v0.0.0-20170922171312-37c2f522c041/go.mod h1:N5mDOmsrJOB+vfqUK+7DmDyjhSLIIBnXo9lvZJj3MWQ=
 github.com/sirupsen/logrus v1.9.0 h1:trlNQbNUG3OdDrDil03MCb1H2o9nJ1x4/5LYw7byDE0=
 github.com/sirupsen/logrus v1.9.0/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
+github.com/sourcegraph/go-diff v0.7.0 h1:9uLlrd5T46OXs5qpp8L/MTltk0zikUGi0sNNyCpA8G0=
+github.com/sourcegraph/go-diff v0.7.0/go.mod h1:iBszgVvyxdc8SFZ7gm69go2KDdt3ag071iBaWPF6cjs=
 github.com/spf13/cast v1.3.1/go.mod h1:Qx5cxh0v+4UWYiBimWS+eyWzqEqokIECu5etghLkUJE=
 github.com/spf13/cast v1.5.0 h1:rj3WzYc11XZaIZMPKmwP96zkFEnnAmV8s6XbB2aY32w=
 github.com/spf13/cast v1.5.0/go.mod h1:SpXXQ5YoyJw6s3/6cMTQuxvgRl3PCJiyaX9p6b155UU=
@@ -192,6 +197,7 @@ golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtn
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/appengine v1.6.5/go.mod h1:8WjMMxjGQR8xUklV/ARdw2HLXBOI7O7uCIDZVag1xfc=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

internal/stylist/enums.go

@@ -19,7 +19,7 @@ type OutputType string
 
 // OutputFormat represents how to parse command output.
 //
-// ENUM(json, none, regexp, sarif).
+// ENUM(diff, json, none, regexp, sarif).
 type OutputFormat string
 
 // ResultLevel represents the severity level of the result.

internal/stylist/output_parser.go

@@ -5,8 +5,10 @@ import (
 	"fmt"
 	"io"
 	"regexp"
+	"strings"
 
 	"github.com/owenrumney/go-sarif/sarif"
+	"github.com/sourcegraph/go-diff/diff"
 	"github.com/tidwall/gjson"
 
 	"github.com/twelvelabs/stylist/internal/fsutils"
@@ -29,6 +31,8 @@ type OutputParser interface {
 // NewOutputParser returns the appropriate parser for the given output type.
 func NewOutputParser(format OutputFormat) OutputParser { //nolint:ireturn
 	switch format {
+	case OutputFormatDiff:
+		return &DiffOutputParser{}
 	case OutputFormatJson:
 		return &JSONOutputParser{}
 	case OutputFormatNone:
@@ -42,6 +46,76 @@ func NewOutputParser(format OutputFormat) OutputParser { //nolint:ireturn
 	}
 }
 
+/*
+* DiffOutputParser
+**/
+
+// DiffOutputParser parses unified diffs.
+type DiffOutputParser struct {
+}
+
+// Parse parses command output into a slice of results.
+func (p *DiffOutputParser) Parse(output CommandOutput, mapping ResultMapping) ([]*Result, error) {
+	// Read the content.
+	buf, err := io.ReadAll(output.Content)
+	if err != nil {
+		return nil, err
+	}
+	content := ansiRegexp.ReplaceAll(buf, []byte(""))
+	if len(content) == 0 {
+		return nil, nil // nothing to parse
+	}
+
+	// Parse.
+	diffs, err := diff.ParseMultiFileDiff(content)
+	if err != nil {
+		return nil, fmt.Errorf("invalid diff: %w", err)
+	}
+
+	// Map the diffs to a slice of `Result` structs.
+	results := []*Result{}
+	for _, d := range diffs {
+		var startLine int
+		var contextLines []string
+
+		if len(d.Hunks) > 0 {
+			// Hunks often start w/ a few preceding context lines.
+			// Calculate the actual start of the changeset.
+			changeStart := 0
+			bodyLines := bytes.Split(d.Hunks[0].Body, []byte{'\n'})
+			for _, line := range bodyLines {
+				if len(line) > 0 && (line[0] == '+' || line[0] == '-') {
+					break
+				}
+				changeStart++
+			}
+			startLine = int(d.Hunks[0].OrigStartLine) + changeStart
+
+			// Printing just the hunks (vs full diff) so we don't have
+			// redundant file names at the top of the context.
+			hunks, _ := diff.PrintHunks(d.Hunks)
+			contextLines = strings.Split(strings.TrimSuffix(string(hunks), "\n"), "\n")
+		}
+
+		result := &Result{
+			Level: ResultLevelError,
+			Location: ResultLocation{
+				Path:      d.NewName,
+				StartLine: startLine,
+			},
+			Rule: ResultRule{
+				ID:          "diff",
+				Name:        "diff",
+				Description: "Formatting error",
+			},
+			ContextLines: contextLines,
+		}
+		results = append(results, result)
+	}
+
+	return results, nil
+}
+
 /*
 * JSONOutputParser
 **/

internal/stylist/output_parser_test.go

@@ -33,6 +33,105 @@ func TestNewOutputParser(t *testing.T) {
 	})
 }
 
+func TestDiffOutputParser_Parse(t *testing.T) {
+	tests := []struct {
+		desc     string
+		content  io.Reader
+		expected []*Result
+		err      string
+	}{
+		{
+			desc:     "returns an empty slice when no content",
+			content:  bytes.NewBufferString(""),
+			expected: nil,
+			err:      "",
+		},
+		{
+			desc:     "returns an empty slice when not a valid diff",
+			content:  bytes.NewBufferString("not a diff"),
+			expected: []*Result{},
+			err:      "",
+		},
+		{
+			desc:    "parses diffs",
+			content: mustOpenFile("testdata/output/shfmt.diff"),
+			expected: []*Result{
+				{
+					Level: ResultLevelError,
+					Location: ResultLocation{
+						Path:      "bin/command.sh",
+						StartLine: 4,
+					},
+					Rule: ResultRule{
+						ID:          "diff",
+						Name:        "diff",
+						Description: "Formatting error",
+					},
+					ContextLines: []string{
+						"@@ -1,10 +1,10 @@",
+						" #!/usr/bin/env bash",
+						" set -o errexit -o errtrace -o nounset -o pipefail",
+						"",
+						"-",
+						"-if [",
+						"+if",
+						"+    [",
+						"     $foo == \"bar\"",
+						"-]",
+						"+    ]",
+						" then",
+						"     echo \"lol\"",
+						" fi",
+					},
+				},
+				{
+					Level: ResultLevelError,
+					Location: ResultLocation{
+						Path:      "bin/entrypoint.sh",
+						StartLine: 19,
+					},
+					Rule: ResultRule{
+						ID:          "diff",
+						Name:        "diff",
+						Description: "Formatting error",
+					},
+					ContextLines: []string{
+						"@@ -16,8 +16,8 @@",
+						"     # fix permissions",
+						"     sudo chown -R app:app \\",
+						"         /app \\",
+						"-            /home/app \\",
+						"-                /run/host-services/ssh-auth.sock",
+						"+        /home/app \\",
+						"+        /run/host-services/ssh-auth.sock",
+						" fi",
+						"",
+					},
+				},
+			},
+			err: "",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.desc, func(t *testing.T) {
+			actual, err := (&DiffOutputParser{}).Parse(
+				CommandOutput{
+					Content: tt.content,
+				},
+				ResultMapping{},
+			)
+
+			if tt.err == "" {
+				assert.NoError(t, err)
+			} else {
+				assert.ErrorContains(t, err, tt.err)
+			}
+
+			assert.Equal(t, tt.expected, actual)
+		})
+	}
+}
+
 func TestJSONOutputParser_Parse(t *testing.T) {
 	file, err := os.Open("testdata/output/shellcheck.json")
 	assert.NoError(t, err)

internal/stylist/presets.yml

@@ -70,6 +70,23 @@ golangci-lint:
     output: stdout
     format: none
 
+gofmt:
+  name: gofmt
+  preset: gofmt
+  tags: []
+  includes:
+    - "**/*.go"
+  check:
+    command: "gofmt -d"
+    input: variadic
+    output: stdout
+    format: diff
+  fix:
+    command: "gofmt -w"
+    input: variadic
+    output: stdout
+    format: none
+
 hadolint:
   name: hadolint
   preset: hadolint
@@ -141,3 +158,20 @@ shellcheck:
       rule_name: "SC{{ .code }}"
       rule_description: "{{ .message }}"
       rule_uri: "https://www.shellcheck.net/wiki/SC{{ .code }}"
+
+shfmt:
+  name: shfmt
+  preset: shfmt
+  tags: []
+  includes:
+    - "**/*.{bash,sh,shell}"
+  check:
+    command: "shfmt --diff"
+    input: variadic
+    output: stdout
+    format: diff
+  fix:
+    command: "shfmt --write"
+    input: variadic
+    output: stdout
+    format: none

internal/stylist/testdata/output/shfmt.diff

@@ -0,0 +1,28 @@
+--- bin/command.sh.orig
++++ bin/command.sh
+@@ -1,10 +1,10 @@
+ #!/usr/bin/env bash
+ set -o errexit -o errtrace -o nounset -o pipefail
+
+-
+-if [
++if
++    [
+     $foo == "bar"
+-]
++    ]
+ then
+     echo "lol"
+ fi
+--- bin/entrypoint.sh.orig
++++ bin/entrypoint.sh
+@@ -16,8 +16,8 @@
+     # fix permissions
+     sudo chown -R app:app \
+         /app \
+-            /home/app \
+-                /run/host-services/ssh-auth.sock
++        /home/app \
++        /run/host-services/ssh-auth.sock
+ fi
+