feat: coverage diff

.testcoverage.example.yml

@@ -43,4 +43,13 @@ exclude:
   # Exclude files or packages matching their paths
   paths:
     - \.pb\.go$    # excludes all protobuf generated files
-    - ^pkg/bar     # exclude package `pkg/bar`
+    - ^pkg/bar     # exclude package `pkg/bar`
+
+# File name of go-test-coverage breakdown file, which can be used to 
+# analyze coverage difference.
+breakdown-file-name: ''
+
+diff:
+  # File name of go-test-coverage breakdown file which will be used to 
+  # report coverage difference.
+  base-breakdown-file-name: ''

Makefile

@@ -22,7 +22,7 @@ lint: get-golangcilint
 .PHONY: test
 test: 
 	go test -timeout=3s -race -count=10 -failfast -shuffle=on -short ./...
-	go test -timeout=10s -race -count=1 -failfast  -shuffle=on ./... -coverprofile=./cover.profile -covermode=atomic -coverpkg=./...
+	go test -timeout=20s -race -count=1 -failfast  -shuffle=on ./... -coverprofile=./cover.profile -covermode=atomic -coverpkg=./...
 
 # Runs test coverage check
 .PHONY: check-coverage

README.md

@@ -126,6 +126,15 @@ exclude:
   paths:
     - \.pb\.go$    # excludes all protobuf generated files
     - ^pkg/bar     # exclude package `pkg/bar`
+
+# File name of go-test-coverage breakdown file, which can be used to 
+# analyze coverage difference.
+breakdown-file-name: ''
+
+diff:
+  # File name of go-test-coverage breakdown file which will be used to 
+  # report coverage difference.
+  base-breakdown-file-name: ''
 ```
 
 ### Exclude Code from Coverage

action.yml

@@ -36,6 +36,18 @@ inputs:
     default: -1
     type: number
 
+  breakdown-file-name:
+    description: File name of go-test-coverage breakdown file, which can be used to analyze coverage difference. Overrides value from configuration.
+    required: false
+    default: ""
+    type: string
+
+  diff-base-breakdown-file-name:
+    description: File name of go-test-coverage breakdown file used to calculate coverage difference from current (head).
+    required: false
+    default: ""
+    type: string
+
   # Badge (as file)
   badge-file-name:
     description: If specified, a coverage badge will be generated and saved to the given file path.
@@ -123,6 +135,8 @@ runs:
     - --threshold-file=${{ inputs.threshold-file }}
     - --threshold-package=${{ inputs.threshold-package }}
     - --threshold-total=${{ inputs.threshold-total }}
+    - --breakdown-file-name=${{ inputs.breakdown-file-name || '''''' }}
+    - --diff-base-breakdown-file-name=${{ inputs.diff-base-breakdown-file-name || '''''' }}
     - --badge-file-name=${{ inputs.badge-file-name || '''''' }}
     - --cdn-key=${{ inputs.cdn-key || '''''' }}
     - --cdn-secret=${{ inputs.cdn-secret || '''''' }}

main.go

@@ -31,7 +31,11 @@ type args struct {
 	ThresholdFile      int    `arg:"-f,--threshold-file"`
 	ThresholdPackage   int    `arg:"-k,--threshold-package"`
 	ThresholdTotal     int    `arg:"-t,--threshold-total"`
-	BadgeFileName      string `arg:"-b,--badge-file-name"`
+
+	BreakdownFileName         string `arg:"--breakdown-file-name"`
+	DiffBaseBreakdownFileName string `arg:"--diff-base-breakdown-file-name"`
+
+	BadgeFileName string `arg:"-b,--badge-file-name"`
 
 	CDNKey            string `arg:"--cdn-key"`
 	CDNSecret         string `arg:"--cdn-secret"`
@@ -57,6 +61,9 @@ func newArgs() args {
 		ThresholdPackage:   ciDefaultInt,
 		ThresholdTotal:     ciDefaultInt,
 
+		BreakdownFileName:         ciDefaultString,
+		DiffBaseBreakdownFileName: ciDefaultString,
+
 		// Badge
 		BadgeFileName: ciDefaultString,
 
@@ -81,7 +88,7 @@ func (args) Version() string {
 	return Name + " " + Version
 }
 
-//nolint:cyclop,maintidx,mnd // relax
+//nolint:cyclop,maintidx,mnd,funlen // relax
 func (a *args) overrideConfig(cfg testcoverage.Config) (testcoverage.Config, error) {
 	if !isCIDefaultString(a.Profile) {
 		cfg.Profile = a.Profile
@@ -107,6 +114,14 @@ func (a *args) overrideConfig(cfg testcoverage.Config) (testcoverage.Config, err
 		cfg.Threshold.Total = a.ThresholdTotal
 	}
 
+	if !isCIDefaultString(a.BreakdownFileName) {
+		cfg.BreakdownFileName = a.BreakdownFileName
+	}
+
+	if !isCIDefaultString(a.DiffBaseBreakdownFileName) {
+		cfg.Diff.BaseBreakdownFileName = a.DiffBaseBreakdownFileName
+	}
+
 	if !isCIDefaultString(a.BadgeFileName) {
 		cfg.Badge.FileName = a.BadgeFileName
 	}

pkg/testcoverage/check.go

@@ -5,23 +5,32 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"os"
 	"strings"
 
 	"github.com/vladopajic/go-test-coverage/v2/pkg/testcoverage/coverage"
 )
 
 func Check(w io.Writer, cfg Config) bool {
-	stats, err := coverage.GenerateCoverageStats(coverage.Config{
-		Profiles:     strings.Split(cfg.Profile, ","),
-		LocalPrefix:  cfg.LocalPrefix,
-		ExcludePaths: cfg.Exclude.Paths,
-	})
+	currentStats, err := GenerateCoverageStats(cfg)
 	if err != nil {
 		fmt.Fprintf(w, "failed to generate coverage statistics: %v\n", err)
 		return false
 	}
 
-	result := Analyze(cfg, stats)
+	err = saveCoverageBreakdown(cfg, currentStats)
+	if err != nil {
+		fmt.Fprintf(w, "failed to save coverage breakdown: %v\n", err)
+		return false
+	}
+
+	baseStats, err := loadBaseCoverageBreakdown(cfg)
+	if err != nil {
+		fmt.Fprintf(w, "failed to load base coverage breakdown: %v\n", err)
+		return false
+	}
+
+	result := Analyze(cfg, currentStats, baseStats)
 
 	report := reportForHuman(w, result)
 
@@ -56,16 +65,53 @@ func reportForHuman(w io.Writer, result AnalyzeResult) string {
 	return buffer.String()
 }
 
-func Analyze(cfg Config, coverageStats []coverage.Stats) AnalyzeResult {
+func GenerateCoverageStats(cfg Config) ([]coverage.Stats, error) {
+	return coverage.GenerateCoverageStats(coverage.Config{ //nolint:wrapcheck // err wrapped above
+		Profiles:     strings.Split(cfg.Profile, ","),
+		LocalPrefix:  cfg.LocalPrefix,
+		ExcludePaths: cfg.Exclude.Paths,
+	})
+}
+
+func Analyze(cfg Config, current, base []coverage.Stats) AnalyzeResult {
 	thr := cfg.Threshold
 	overrideRules := compileOverridePathRules(cfg)
 
 	return AnalyzeResult{
 		Threshold:           thr,
-		FilesBelowThreshold: checkCoverageStatsBelowThreshold(coverageStats, thr.File, overrideRules),
+		FilesBelowThreshold: checkCoverageStatsBelowThreshold(current, thr.File, overrideRules),
 		PackagesBelowThreshold: checkCoverageStatsBelowThreshold(
-			makePackageStats(coverageStats), thr.Package, overrideRules,
+			makePackageStats(current), thr.Package, overrideRules,
 		),
-		TotalStats: coverage.CalcTotalStats(coverageStats),
+		TotalStats:       coverage.CalcTotalStats(current),
+		HasBaseBreakdown: len(base) > 0,
+		Diff:             calculateStatsDiff(current, base),
+	}
+}
+
+func saveCoverageBreakdown(cfg Config, stats []coverage.Stats) error {
+	if cfg.BreakdownFileName == "" {
+		return nil
+	}
+
+	//nolint:mnd,wrapcheck,gosec // relax
+	return os.WriteFile(cfg.BreakdownFileName, coverage.SerializeStats(stats), 0o644)
+}
+
+func loadBaseCoverageBreakdown(cfg Config) ([]coverage.Stats, error) {
+	if cfg.Diff.BaseBreakdownFileName == "" {
+		return nil, nil
+	}
+
+	data, err := os.ReadFile(cfg.Diff.BaseBreakdownFileName)
+	if err != nil {
+		return nil, fmt.Errorf("reading file content failed: %w", err)
 	}
+
+	stats, err := coverage.DeserializeStats(data)
+	if err != nil {
+		return nil, fmt.Errorf("parsing file failed: %w", err)
+	}
+
+	return stats, nil
 }