From ce72bd4019fc8148af56b101d0fc037d52a05f10 Mon Sep 17 00:00:00 2001
From: Leon Sodhi <leon.sodhi@leadfeeder.com>
Date: Mon, 18 Nov 2019 19:09:43 +0000
Subject: [PATCH] Allow modified files to be excluded

---
 server/events/project_finder.go      | 21 +++++++++---
 server/events/project_finder_test.go | 48 ++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+), 4 deletions(-)

diff --git a/server/events/project_finder.go b/server/events/project_finder.go
index f14cb1718..b0db61718 100644
--- a/server/events/project_finder.go
+++ b/server/events/project_finder.go
@@ -82,12 +82,25 @@ func (p *DefaultProjectFinder) DetermineProjectsViaConfig(log *logging.SimpleLog
 	var projects []valid.Project
 	for _, project := range config.Projects {
 		log.Debug("checking if project at dir %q workspace %q was modified", project.Dir, project.Workspace)
-		// Prepend project dir to when modified patterns because the patterns
-		// are relative to the project dirs but our list of modified files is
-		// relative to the repo root.
 		var whenModifiedRelToRepoRoot []string
 		for _, wm := range project.Autoplan.WhenModified {
-			whenModifiedRelToRepoRoot = append(whenModifiedRelToRepoRoot, filepath.Join(project.Dir, wm))
+			wm = strings.TrimSpace(wm)
+			// An exclusion uses a '!' at the beginning. If it's there, we need
+			// to remove it, then add in the project path, then add it back.
+			exclusion := false
+			if wm != "" && wm[0] == '!' {
+				wm = wm[1:]
+				exclusion = true
+			}
+
+			// Prepend project dir to when modified patterns because the patterns
+			// are relative to the project dirs but our list of modified files is
+			// relative to the repo root.
+			wmRelPath := filepath.Join(project.Dir, wm)
+			if exclusion {
+				wmRelPath = "!" + wmRelPath
+			}
+			whenModifiedRelToRepoRoot = append(whenModifiedRelToRepoRoot, wmRelPath)
 		}
 		pm, err := fileutils.NewPatternMatcher(whenModifiedRelToRepoRoot)
 		if err != nil {
diff --git a/server/events/project_finder_test.go b/server/events/project_finder_test.go
index 5a0d0304d..5b10325e4 100644
--- a/server/events/project_finder_test.go
+++ b/server/events/project_finder_test.go
@@ -396,6 +396,54 @@ func TestDefaultProjectFinder_DetermineProjectsViaConfig(t *testing.T) {
 			modified:     []string{"project2/terraform.tfvars"},
 			expProjPaths: []string{"project2"},
 		},
+		{
+			description: "file excluded",
+			config: valid.RepoCfg{
+				Projects: []valid.Project{
+					{
+						Dir: "project1",
+						Autoplan: valid.Autoplan{
+							Enabled:      true,
+							WhenModified: []string{"*.tf", "!exclude-me.tf"},
+						},
+					},
+				},
+			},
+			modified:     []string{"project1/exclude-me.tf"},
+			expProjPaths: nil,
+		},
+		{
+			description: "some files excluded and others included",
+			config: valid.RepoCfg{
+				Projects: []valid.Project{
+					{
+						Dir: "project1",
+						Autoplan: valid.Autoplan{
+							Enabled:      true,
+							WhenModified: []string{"*.tf", "!exclude-me.tf"},
+						},
+					},
+				},
+			},
+			modified:     []string{"project1/exclude-me.tf", "project1/include-me.tf"},
+			expProjPaths: []string{"project1"},
+		},
+		{
+			description: "multiple dirs excluded",
+			config: valid.RepoCfg{
+				Projects: []valid.Project{
+					{
+						Dir: "project1",
+						Autoplan: valid.Autoplan{
+							Enabled:      true,
+							WhenModified: []string{"**/*.tf", "!subdir1/*", "!subdir2/*"},
+						},
+					},
+				},
+			},
+			modified:     []string{"project1/subdir1/main.tf", "project1/subdir2/main.tf"},
+			expProjPaths: nil,
+		},
 	}
 
 	for _, c := range cases {