feat: add autodiscover enabled feature (#3895)

* add flag to allow the user disable the autodiscover

* add global config and doc

* feat: Implement autodiscover.mode

* fix: Minor doc fixes

* fix: Small fixes to docs/indent/tests

* fix: Line length, quoting, function comments

* fix: Add a few more tests and remove newlines

* fix: Always camel case never snake

---------

Co-authored-by: Marcelo Medeiros <m.medeiros@carepay.com>
Co-authored-by: nitrocode <7775707+nitrocode@users.noreply.github.com>
Co-authored-by: PePe Amengual <jose.amengual@gmail.com>

server/core/config/parser_validator_test.go

@@ -1329,6 +1329,22 @@ func TestParseGlobalCfg(t *testing.T) {
   import_requirements: [invalid]`,
 			expErr: "repos: (0: (import_requirements: \"invalid\" is not a valid import_requirement, only \"approved\", \"mergeable\" and \"undiverged\" are supported.).).",
 		},
+		"disable autodiscover": {
+			input: `repos: 
+- id: /.*/
+  autodiscover:
+    mode: disabled`,
+			exp: valid.GlobalCfg{
+				Repos: []valid.Repo{
+					defaultCfg.Repos[0],
+					{
+						IDRegex:      regexp.MustCompile(".*"),
+						AutoDiscover: &valid.AutoDiscover{Mode: valid.AutoDiscoverDisabledMode},
+					},
+				},
+				Workflows: defaultCfg.Workflows,
+			},
+		},
 		"no workflows key": {
 			input: `repos: []`,
 			exp:   defaultCfg,
@@ -1404,6 +1420,8 @@ repos:
   allowed_overrides: [plan_requirements, apply_requirements, import_requirements, workflow, delete_source_branch_on_merge]
   allow_custom_workflows: true
   policy_check: true
+  autodiscover:
+    mode: enabled
 - id: /.*/
   branch: /(master|main)/
   pre_workflow_hooks:
@@ -1411,6 +1429,8 @@ repos:
   post_workflow_hooks:
     - run: custom workflow command
   policy_check: false
+  autodiscover:
+    mode: disabled
 workflows:
   custom1:
     plan:
@@ -1457,6 +1477,7 @@ policies:
 						AllowedOverrides:     []string{"plan_requirements", "apply_requirements", "import_requirements", "workflow", "delete_source_branch_on_merge"},
 						AllowCustomWorkflows: Bool(true),
 						PolicyCheck:          Bool(true),
+						AutoDiscover:         &valid.AutoDiscover{Mode: valid.AutoDiscoverEnabledMode},
 					},
 					{
 						IDRegex:           regexp.MustCompile(".*"),
@@ -1464,6 +1485,7 @@ policies:
 						PreWorkflowHooks:  preWorkflowHooks,
 						PostWorkflowHooks: postWorkflowHooks,
 						PolicyCheck:       Bool(false),
+						AutoDiscover:      &valid.AutoDiscover{Mode: valid.AutoDiscoverDisabledMode},
 					},
 				},
 				Workflows: map[string]valid.Workflow{
@@ -1574,6 +1596,7 @@ workflows:
 						RepoLocking:               Bool(true),
 						PolicyCheck:               Bool(false),
 						CustomPolicyCheck:         Bool(false),
+						AutoDiscover:              raw.DefaultAutoDiscover(),
 					},
 				},
 				Workflows: map[string]valid.Workflow{
@@ -1727,7 +1750,10 @@ func TestParserValidator_ParseGlobalCfgJSON(t *testing.T) {
       "allowed_workflows": ["custom"],
       "apply_requirements": ["mergeable", "approved"],
       "allowed_overrides": ["workflow", "apply_requirements"],
-      "allow_custom_workflows": true
+      "allow_custom_workflows": true,
+      "autodiscover": {
+        "mode": "enabled"
+      }
     },
     {
       "id": "github.com/owner/repo"
@@ -1792,6 +1818,7 @@ func TestParserValidator_ParseGlobalCfgJSON(t *testing.T) {
 						AllowedWorkflows:     []string{"custom"},
 						AllowedOverrides:     []string{"workflow", "apply_requirements"},
 						AllowCustomWorkflows: Bool(true),
+						AutoDiscover:         &valid.AutoDiscover{Mode: valid.AutoDiscoverEnabledMode},
 					},
 					{
 						ID:                   "github.com/owner/repo",
@@ -1799,6 +1826,7 @@ func TestParserValidator_ParseGlobalCfgJSON(t *testing.T) {
 						ApplyRequirements:    nil,
 						AllowedOverrides:     nil,
 						AllowCustomWorkflows: nil,
+						AutoDiscover:         nil,
 					},
 				},
 				Workflows: map[string]valid.Workflow{

server/core/config/raw/autodiscover.go

@@ -0,0 +1,38 @@
+package raw
+
+import (
+	validation "github.com/go-ozzo/ozzo-validation"
+	"github.com/runatlantis/atlantis/server/core/config/valid"
+)
+
+var DefaultAutoDiscoverMode = valid.AutoDiscoverAutoMode
+
+type AutoDiscover struct {
+	Mode *valid.AutoDiscoverMode `yaml:"mode,omitempty"`
+}
+
+func (a AutoDiscover) ToValid() *valid.AutoDiscover {
+	var v valid.AutoDiscover
+
+	if a.Mode != nil {
+		v.Mode = *a.Mode
+	} else {
+		v.Mode = DefaultAutoDiscoverMode
+	}
+
+	return &v
+}
+
+func (a AutoDiscover) Validate() error {
+	res := validation.ValidateStruct(&a,
+		// If a.Mode is nil, this should still pass validation.
+		validation.Field(&a.Mode, validation.In(valid.AutoDiscoverAutoMode, valid.AutoDiscoverDisabledMode, valid.AutoDiscoverEnabledMode)),
+	)
+	return res
+}
+
+func DefaultAutoDiscover() *valid.AutoDiscover {
+	return &valid.AutoDiscover{
+		Mode: DefaultAutoDiscoverMode,
+	}
+}

server/core/config/raw/autodiscover_test.go

@@ -0,0 +1,131 @@
+package raw_test
+
+import (
+	"testing"
+
+	"github.com/runatlantis/atlantis/server/core/config/raw"
+	"github.com/runatlantis/atlantis/server/core/config/valid"
+	. "github.com/runatlantis/atlantis/testing"
+	yaml "gopkg.in/yaml.v2"
+)
+
+func TestAutoDiscover_UnmarshalYAML(t *testing.T) {
+	autoDiscoverEnabled := valid.AutoDiscoverEnabledMode
+	cases := []struct {
+		description string
+		input       string
+		exp         raw.AutoDiscover
+	}{
+		{
+			description: "omit unset fields",
+			input:       "",
+			exp: raw.AutoDiscover{
+				Mode: nil,
+			},
+		},
+		{
+			description: "all fields set",
+			input: `
+mode: enabled
+`,
+			exp: raw.AutoDiscover{
+				Mode: &autoDiscoverEnabled,
+			},
+		},
+	}
+
+	for _, c := range cases {
+		t.Run(c.description, func(t *testing.T) {
+			var a raw.AutoDiscover
+			err := yaml.UnmarshalStrict([]byte(c.input), &a)
+			Ok(t, err)
+			Equals(t, c.exp, a)
+		})
+	}
+}
+
+func TestAutoDiscover_Validate(t *testing.T) {
+	autoDiscoverAuto := valid.AutoDiscoverAutoMode
+	autoDiscoverEnabled := valid.AutoDiscoverEnabledMode
+	autoDiscoverDisabled := valid.AutoDiscoverDisabledMode
+	randomString := valid.AutoDiscoverMode("random_string")
+	cases := []struct {
+		description string
+		input       raw.AutoDiscover
+		errContains *string
+	}{
+		{
+			description: "nothing set",
+			input:       raw.AutoDiscover{},
+			errContains: nil,
+		},
+		{
+			description: "mode set to auto",
+			input: raw.AutoDiscover{
+				Mode: &autoDiscoverAuto,
+			},
+			errContains: nil,
+		},
+		{
+			description: "mode set to disabled",
+			input: raw.AutoDiscover{
+				Mode: &autoDiscoverDisabled,
+			},
+			errContains: nil,
+		},
+		{
+			description: "mode set to enabled",
+			input: raw.AutoDiscover{
+				Mode: &autoDiscoverEnabled,
+			},
+			errContains: nil,
+		},
+		{
+			description: "mode set to random string",
+			input: raw.AutoDiscover{
+				Mode: &randomString,
+			},
+			errContains: String("valid value"),
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.description, func(t *testing.T) {
+			if c.errContains == nil {
+				Ok(t, c.input.Validate())
+			} else {
+				ErrContains(t, *c.errContains, c.input.Validate())
+			}
+		})
+	}
+}
+
+func TestAutoDiscover_ToValid(t *testing.T) {
+	autoDiscoverEnabled := valid.AutoDiscoverEnabledMode
+	cases := []struct {
+		description string
+		input       raw.AutoDiscover
+		exp         *valid.AutoDiscover
+	}{
+		{
+			description: "nothing set",
+			input:       raw.AutoDiscover{},
+			exp: &valid.AutoDiscover{
+				Mode: valid.AutoDiscoverAutoMode,
+			},
+		},
+		{
+			description: "value set",
+			input: raw.AutoDiscover{
+				Mode: &autoDiscoverEnabled,
+			},
+			exp: &valid.AutoDiscover{
+				Mode: valid.AutoDiscoverEnabledMode,
+			},
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.description, func(t *testing.T) {
+			Equals(t, c.exp, c.input.ToValid())
+		})
+	}
+}

server/core/config/raw/global_cfg.go

@@ -36,6 +36,7 @@ type Repo struct {
 	RepoLocking               *bool          `yaml:"repo_locking,omitempty" json:"repo_locking,omitempty"`
 	PolicyCheck               *bool          `yaml:"policy_check,omitempty" json:"policy_check,omitempty"`
 	CustomPolicyCheck         *bool          `yaml:"custom_policy_check,omitempty" json:"custom_policy_check,omitempty"`
+	AutoDiscover              *AutoDiscover  `yaml:"autodiscover,omitempty" json:"autodiscover,omitempty"`
 }
 
 func (g GlobalCfg) Validate() error {
@@ -211,6 +212,14 @@ func (r Repo) Validate() error {
 		return nil
 	}
 
+	autoDiscoverValid := func(value interface{}) error {
+		autoDiscover := value.(*AutoDiscover)
+		if autoDiscover != nil {
+			return autoDiscover.Validate()
+		}
+		return nil
+	}
+
 	return validation.ValidateStruct(&r,
 		validation.Field(&r.ID, validation.Required, validation.By(idValid)),
 		validation.Field(&r.Branch, validation.By(branchValid)),
@@ -221,6 +230,7 @@ func (r Repo) Validate() error {
 		validation.Field(&r.ImportRequirements, validation.By(validImportReq)),
 		validation.Field(&r.Workflow, validation.By(workflowExists)),
 		validation.Field(&r.DeleteSourceBranchOnMerge, validation.By(deleteSourceBranchOnMergeValid)),
+		validation.Field(&r.AutoDiscover, validation.By(autoDiscoverValid)),
 	)
 }
 
@@ -281,7 +291,7 @@ OuterGlobalPlanReqs:
 		}
 
 		// dont add policy_check step if repo have it explicitly disabled
-		if globalReq == valid.PoliciesPassedCommandReq && r.PolicyCheck != nil && *r.PolicyCheck == false {
+		if globalReq == valid.PoliciesPassedCommandReq && r.PolicyCheck != nil && !*r.PolicyCheck {
 			continue
 		}
 		mergedPlanReqs = append(mergedPlanReqs, globalReq)
@@ -295,7 +305,7 @@ OuterGlobalApplyReqs:
 		}
 
 		// dont add policy_check step if repo have it explicitly disabled
-		if globalReq == valid.PoliciesPassedCommandReq && r.PolicyCheck != nil && *r.PolicyCheck == false {
+		if globalReq == valid.PoliciesPassedCommandReq && r.PolicyCheck != nil && !*r.PolicyCheck {
 			continue
 		}
 		mergedApplyReqs = append(mergedApplyReqs, globalReq)
@@ -309,12 +319,17 @@ OuterGlobalImportReqs:
 		}
 
 		// dont add policy_check step if repo have it explicitly disabled
-		if globalReq == valid.PoliciesPassedCommandReq && r.PolicyCheck != nil && *r.PolicyCheck == false {
+		if globalReq == valid.PoliciesPassedCommandReq && r.PolicyCheck != nil && !*r.PolicyCheck {
 			continue
 		}
 		mergedImportReqs = append(mergedImportReqs, globalReq)
 	}
 
+	var autoDiscover *valid.AutoDiscover
+	if r.AutoDiscover != nil {
+		autoDiscover = r.AutoDiscover.ToValid()
+	}
+
 	return valid.Repo{
 		ID:                        id,
 		IDRegex:                   idRegex,
@@ -333,5 +348,6 @@ OuterGlobalImportReqs:
 		RepoLocking:               r.RepoLocking,
 		PolicyCheck:               r.PolicyCheck,
 		CustomPolicyCheck:         r.CustomPolicyCheck,
+		AutoDiscover:              autoDiscover,
 	}
 }

server/core/config/raw/repo_cfg.go

@@ -19,6 +19,7 @@ type RepoCfg struct {
 	Projects                   []Project           `yaml:"projects,omitempty"`
 	Workflows                  map[string]Workflow `yaml:"workflows,omitempty"`
 	PolicySets                 PolicySets          `yaml:"policies,omitempty"`
+	AutoDiscover               *AutoDiscover       `yaml:"autodiscover,omitempty"`
 	Automerge                  *bool               `yaml:"automerge,omitempty"`
 	ParallelApply              *bool               `yaml:"parallel_apply,omitempty"`
 	ParallelPlan               *bool               `yaml:"parallel_plan,omitempty"`
@@ -71,10 +72,16 @@ func (r RepoCfg) ToValid() valid.RepoCfg {
 		abortOnExcecutionOrderFail = *r.AbortOnExcecutionOrderFail
 	}
 
+	var autoDiscover *valid.AutoDiscover
+	if r.AutoDiscover != nil {
+		autoDiscover = r.AutoDiscover.ToValid()
+	}
+
 	return valid.RepoCfg{
 		Version:                    *r.Version,
 		Projects:                   validProjects,
 		Workflows:                  validWorkflows,
+		AutoDiscover:               autoDiscover,
 		Automerge:                  automerge,
 		ParallelApply:              parallelApply,
 		ParallelPlan:               parallelPlan,

server/core/config/raw/repo_cfg_test.go

@@ -11,6 +11,7 @@ import (
 )
 
 func TestConfig_UnmarshalYAML(t *testing.T) {
+	autoDiscoverEnabled := valid.AutoDiscoverEnabledMode
 	cases := []struct {
 		description string
 		input       string
@@ -126,6 +127,8 @@ func TestConfig_UnmarshalYAML(t *testing.T) {
 			input: `
 version: 3
 automerge: true
+autodiscover:
+  mode: enabled
 parallel_apply: true
 parallel_plan: false
 projects:
@@ -150,6 +153,7 @@ allowed_regexp_prefixes:
 - staging/`,
 			exp: raw.RepoCfg{
 				Version:       Int(3),
+				AutoDiscover:  &raw.AutoDiscover{Mode: &autoDiscoverEnabled},
 				Automerge:     Bool(true),
 				ParallelApply: Bool(true),
 				ParallelPlan:  Bool(false),
@@ -232,6 +236,7 @@ func TestConfig_Validate(t *testing.T) {
 }
 
 func TestConfig_ToValid(t *testing.T) {
+	autoDiscoverEnabled := valid.AutoDiscoverEnabledMode
 	cases := []struct {
 		description string
 		input       raw.RepoCfg
@@ -248,18 +253,20 @@ func TestConfig_ToValid(t *testing.T) {
 		{
 			description: "set to empty",
 			input: raw.RepoCfg{
-				Version:   Int(2),
-				Workflows: map[string]raw.Workflow{},
-				Projects:  []raw.Project{},
+				Version:      Int(2),
+				AutoDiscover: &raw.AutoDiscover{},
+				Workflows:    map[string]raw.Workflow{},
+				Projects:     []raw.Project{},
 			},
 			exp: valid.RepoCfg{
-				Version:   2,
-				Workflows: map[string]valid.Workflow{},
-				Projects:  nil,
+				Version:      2,
+				AutoDiscover: raw.DefaultAutoDiscover(),
+				Workflows:    map[string]valid.Workflow{},
+				Projects:     nil,
 			},
 		},
 		{
-			description: "automerge, parallel_apply and abort_on_execution_order_fail omitted",
+			description: "automerge, parallel_apply, abort_on_execution_order_fail omitted",
 			input: raw.RepoCfg{
 				Version: Int(2),
 			},
@@ -272,7 +279,7 @@ func TestConfig_ToValid(t *testing.T) {
 			},
 		},
 		{
-			description: "automerge, parallel_apply and abort_on_execution_order_fail true",
+			description: "automerge, parallel_apply, abort_on_execution_order_fail true",
 			input: raw.RepoCfg{
 				Version:                    Int(2),
 				Automerge:                  Bool(true),
@@ -288,7 +295,7 @@ func TestConfig_ToValid(t *testing.T) {
 			},
 		},
 		{
-			description: "automerge, parallel_apply and abort_on_execution_order_fail false",
+			description: "automerge, parallel_apply, abort_on_execution_order_fail false",
 			input: raw.RepoCfg{
 				Version:                    Int(2),
 				Automerge:                  Bool(false),
@@ -303,6 +310,30 @@ func TestConfig_ToValid(t *testing.T) {
 				Workflows:                  map[string]valid.Workflow{},
 			},
 		},
+		{
+			description: "autodiscover omitted",
+			input: raw.RepoCfg{
+				Version: Int(2),
+			},
+			exp: valid.RepoCfg{
+				Version:   2,
+				Workflows: map[string]valid.Workflow{},
+			},
+		},
+		{
+			description: "autodiscover included",
+			input: raw.RepoCfg{
+				Version:      Int(2),
+				AutoDiscover: &raw.AutoDiscover{Mode: &autoDiscoverEnabled},
+			},
+			exp: valid.RepoCfg{
+				Version: 2,
+				AutoDiscover: &valid.AutoDiscover{
+					Mode: valid.AutoDiscoverEnabledMode,
+				},
+				Workflows: map[string]valid.Workflow{},
+			},
+		},
 		{
 			description: "only plan stage set",
 			input: raw.RepoCfg{
@@ -339,6 +370,9 @@ func TestConfig_ToValid(t *testing.T) {
 				Version:       Int(2),
 				Automerge:     Bool(true),
 				ParallelApply: Bool(true),
+				AutoDiscover: &raw.AutoDiscover{
+					Mode: &autoDiscoverEnabled,
+				},
 				Workflows: map[string]raw.Workflow{
 					"myworkflow": {
 						Apply: &raw.Stage{
@@ -388,6 +422,9 @@ func TestConfig_ToValid(t *testing.T) {
 				Version:       2,
 				Automerge:     Bool(true),
 				ParallelApply: Bool(true),
+				AutoDiscover: &valid.AutoDiscover{
+					Mode: valid.AutoDiscoverEnabledMode,
+				},
 				Workflows: map[string]valid.Workflow{
 					"myworkflow": {
 						Name: "myworkflow",

server/core/config/valid/autodiscover.go

@@ -0,0 +1,14 @@
+package valid
+
+// AutoDiscoverMode enum
+type AutoDiscoverMode string
+
+const (
+	AutoDiscoverEnabledMode  AutoDiscoverMode = "enabled"
+	AutoDiscoverDisabledMode AutoDiscoverMode = "disabled"
+	AutoDiscoverAutoMode     AutoDiscoverMode = "auto"
+)
+
+type AutoDiscover struct {
+	Mode AutoDiscoverMode
+}

server/core/config/valid/global_cfg.go

@@ -28,6 +28,7 @@ const DeleteSourceBranchOnMergeKey = "delete_source_branch_on_merge"
 const RepoLockingKey = "repo_locking"
 const PolicyCheckKey = "policy_check"
 const CustomPolicyCheckKey = "custom_policy_check"
+const AutoDiscoverKey = "autodiscover"
 
 // DefaultAtlantisFile is the default name of the config file for each repo.
 const DefaultAtlantisFile = "atlantis.yaml"
@@ -84,6 +85,7 @@ type Repo struct {
 	RepoLocking               *bool
 	PolicyCheck               *bool
 	CustomPolicyCheck         *bool
+	AutoDiscover              *AutoDiscover
 }
 
 type MergedProjectCfg struct {
@@ -245,6 +247,7 @@ func NewGlobalCfgFromArgs(args GlobalCfgArgs) GlobalCfg {
 	deleteSourceBranchOnMerge := false
 	repoLockingKey := true
 	customPolicyCheck := false
+	autoDiscover := AutoDiscover{Mode: AutoDiscoverAutoMode}
 	if args.AllowRepoCfg {
 		allowedOverrides = []string{PlanRequirementsKey, ApplyRequirementsKey, ImportRequirementsKey, WorkflowKey, DeleteSourceBranchOnMergeKey, RepoLockingKey, PolicyCheckKey}
 		allowCustomWorkflows = true
@@ -269,6 +272,7 @@ func NewGlobalCfgFromArgs(args GlobalCfgArgs) GlobalCfg {
 				RepoLocking:               &repoLockingKey,
 				PolicyCheck:               &policyCheck,
 				CustomPolicyCheck:         &customPolicyCheck,
+				AutoDiscover:              &autoDiscover,
 			},
 		},
 		Workflows: map[string]Workflow{
@@ -305,7 +309,7 @@ func (r Repo) IDString() string {
 // final config. It assumes that all configs have been validated.
 func (g GlobalCfg) MergeProjectCfg(log logging.SimpleLogging, repoID string, proj Project, rCfg RepoCfg) MergedProjectCfg {
 	log.Debug("MergeProjectCfg started")
-	planReqs, applyReqs, importReqs, workflow, allowedOverrides, allowCustomWorkflows, deleteSourceBranchOnMerge, repoLocking, policyCheck, customPolicyCheck := g.getMatchingCfg(log, repoID)
+	planReqs, applyReqs, importReqs, workflow, allowedOverrides, allowCustomWorkflows, deleteSourceBranchOnMerge, repoLocking, policyCheck, customPolicyCheck, _ := g.getMatchingCfg(log, repoID)
 
 	// If repos are allowed to override certain keys then override them.
 	for _, key := range allowedOverrides {
@@ -407,7 +411,7 @@ func (g GlobalCfg) MergeProjectCfg(log logging.SimpleLogging, repoID string, pro
 // repo with id repoID. It is used when there is no repo config.
 func (g GlobalCfg) DefaultProjCfg(log logging.SimpleLogging, repoID string, repoRelDir string, workspace string) MergedProjectCfg {
 	log.Debug("building config based on server-side config")
-	planReqs, applyReqs, importReqs, workflow, _, _, deleteSourceBranchOnMerge, repoLocking, policyCheck, customPolicyCheck := g.getMatchingCfg(log, repoID)
+	planReqs, applyReqs, importReqs, workflow, _, _, deleteSourceBranchOnMerge, repoLocking, policyCheck, customPolicyCheck, _ := g.getMatchingCfg(log, repoID)
 	return MergedProjectCfg{
 		PlanRequirements:          planReqs,
 		ApplyRequirements:         applyReqs,
@@ -426,6 +430,17 @@ func (g GlobalCfg) DefaultProjCfg(log logging.SimpleLogging, repoID string, repo
 	}
 }
 
+// RepoAutoDiscoverCfg returns the AutoDiscover config from the global config
+// for the repo with id repoID. If no matching repo is found or there is no
+// AutoDiscover config then this function returns nil.
+func (g GlobalCfg) RepoAutoDiscoverCfg(repoID string) *AutoDiscover {
+	repo := g.MatchingRepo(repoID)
+	if repo != nil {
+		return repo.AutoDiscover
+	}
+	return nil
+}
+
 // ValidateRepoCfg validates that rCfg for repo with id repoID is valid based
 // on our global config.
 func (g GlobalCfg) ValidateRepoCfg(rCfg RepoCfg, repoID string) error {
@@ -528,7 +543,7 @@ func (g GlobalCfg) ValidateRepoCfg(rCfg RepoCfg, repoID string) error {
 }
 
 // getMatchingCfg returns the key settings for repoID.
-func (g GlobalCfg) getMatchingCfg(log logging.SimpleLogging, repoID string) (planReqs []string, applyReqs []string, importReqs []string, workflow Workflow, allowedOverrides []string, allowCustomWorkflows bool, deleteSourceBranchOnMerge bool, repoLocking bool, policyCheck bool, customPolicyCheck bool) {
+func (g GlobalCfg) getMatchingCfg(log logging.SimpleLogging, repoID string) (planReqs []string, applyReqs []string, importReqs []string, workflow Workflow, allowedOverrides []string, allowCustomWorkflows bool, deleteSourceBranchOnMerge bool, repoLocking bool, policyCheck bool, customPolicyCheck bool, autoDiscover AutoDiscover) {
 	toLog := make(map[string]string)
 	traceF := func(repoIdx int, repoID string, key string, val interface{}) string {
 		from := "default server config"
@@ -550,6 +565,9 @@ func (g GlobalCfg) getMatchingCfg(log logging.SimpleLogging, repoID string) (pla
 		return fmt.Sprintf("setting %s: %s from %s", key, valStr, from)
 	}
 
+	// Can't use raw.DefaultAutoDiscoverMode() because of an import cycle. Should refactor to avoid that.
+	autoDiscover = AutoDiscover{Mode: AutoDiscoverAutoMode}
+
 	for _, key := range []string{PlanRequirementsKey, ApplyRequirementsKey, ImportRequirementsKey, WorkflowKey, AllowedOverridesKey, AllowCustomWorkflowsKey, DeleteSourceBranchOnMergeKey, RepoLockingKey, PolicyCheckKey, CustomPolicyCheckKey} {
 		for i, repo := range g.Repos {
 			if repo.IDMatches(repoID) {
@@ -604,6 +622,11 @@ func (g GlobalCfg) getMatchingCfg(log logging.SimpleLogging, repoID string) (pla
 						toLog[CustomPolicyCheckKey] = traceF(i, repo.IDString(), CustomPolicyCheckKey, *repo.CustomPolicyCheck)
 						customPolicyCheck = *repo.CustomPolicyCheck
 					}
+				case AutoDiscoverKey:
+					if repo.AutoDiscover != nil {
+						toLog[AutoDiscoverKey] = traceF(i, repo.IDString(), AutoDiscoverKey, repo.AutoDiscover.Mode)
+						autoDiscover = *repo.AutoDiscover
+					}
 				}
 			}
 		}

server/core/config/valid/global_cfg_test.go

@@ -10,6 +10,7 @@ import (
 	"github.com/hashicorp/go-version"
 	"github.com/mohae/deepcopy"
 	"github.com/runatlantis/atlantis/server/core/config"
+	"github.com/runatlantis/atlantis/server/core/config/raw"
 	"github.com/runatlantis/atlantis/server/core/config/valid"
 	"github.com/runatlantis/atlantis/server/logging"
 	. "github.com/runatlantis/atlantis/testing"
@@ -82,6 +83,7 @@ func TestNewGlobalCfg(t *testing.T) {
 				RepoLocking:               Bool(true),
 				PolicyCheck:               Bool(false),
 				CustomPolicyCheck:         Bool(false),
+				AutoDiscover:              raw.DefaultAutoDiscover(),
 			},
 		},
 		Workflows: map[string]valid.Workflow{

server/core/config/valid/repo_cfg.go

@@ -19,6 +19,7 @@ type RepoCfg struct {
 	Workflows                  map[string]Workflow
 	PolicySets                 PolicySets
 	Automerge                  *bool
+	AutoDiscover               *AutoDiscover
 	ParallelApply              *bool
 	ParallelPlan               *bool
 	ParallelPolicyCheck        *bool
@@ -91,6 +92,24 @@ func isRegexAllowed(name string, allowedRegexpPrefixes []string) bool {
 	return false
 }
 
+// This function returns a final true/false decision for whether AutoDiscover is enabled
+// for a repo. It takes into account the defaultAutoDiscoverMode when there is no explicit
+// repo config. The defaultAutoDiscoverMode param should be understood as the default
+// AutoDiscover mode as may be set via CLI params or server side repo config.
+func (r RepoCfg) AutoDiscoverEnabled(defaultAutoDiscoverMode AutoDiscoverMode) bool {
+	autoDiscoverMode := defaultAutoDiscoverMode
+	if r.AutoDiscover != nil {
+		autoDiscoverMode = r.AutoDiscover.Mode
+	}
+
+	if autoDiscoverMode == AutoDiscoverAutoMode {
+		// AutoDiscover is enabled by default when no projects are defined
+		return len(r.Projects) == 0
+	}
+
+	return autoDiscoverMode == AutoDiscoverEnabledMode
+}
+
 // validateWorkspaceAllowed returns an error if repoCfg defines projects in
 // repoRelDir but none of them use workspace. We want this to be an error
 // because if users have gone to the trouble of defining projects in repoRelDir

server/core/config/valid/repo_cfg_test.go

@@ -216,3 +216,110 @@ func TestConfig_FindProjectsByDir(t *testing.T) {
 		})
 	}
 }
+
+func TestConfig_AutoDiscoverEnabled(t *testing.T) {
+	cases := []struct {
+		description         string
+		repoAutoDiscover    valid.AutoDiscoverMode
+		defaultAutoDiscover valid.AutoDiscoverMode
+		projects            []valid.Project
+		expEnabled          bool
+	}{
+		{
+			description:         "repo disabled autodiscover default enabled",
+			repoAutoDiscover:    valid.AutoDiscoverDisabledMode,
+			defaultAutoDiscover: valid.AutoDiscoverEnabledMode,
+			expEnabled:          false,
+		},
+		{
+			description:         "repo disabled autodiscover default disabled",
+			repoAutoDiscover:    valid.AutoDiscoverDisabledMode,
+			defaultAutoDiscover: valid.AutoDiscoverDisabledMode,
+			expEnabled:          false,
+		},
+		{
+			description:         "repo enabled autodiscover default enabled",
+			repoAutoDiscover:    valid.AutoDiscoverEnabledMode,
+			defaultAutoDiscover: valid.AutoDiscoverEnabledMode,
+			expEnabled:          true,
+		},
+		{
+			description:         "repo enabled autodiscover default disabled",
+			repoAutoDiscover:    valid.AutoDiscoverEnabledMode,
+			defaultAutoDiscover: valid.AutoDiscoverDisabledMode,
+			expEnabled:          true,
+		},
+		{
+			description:         "repo set auto autodiscover with no projects default enabled",
+			repoAutoDiscover:    valid.AutoDiscoverAutoMode,
+			defaultAutoDiscover: valid.AutoDiscoverEnabledMode,
+			expEnabled:          true,
+		},
+		{
+			description:         "repo set auto autodiscover with no projects default disabled",
+			repoAutoDiscover:    valid.AutoDiscoverAutoMode,
+			defaultAutoDiscover: valid.AutoDiscoverDisabledMode,
+			expEnabled:          true,
+		},
+		{
+			description:         "repo set auto autodiscover with a project default enabled",
+			repoAutoDiscover:    valid.AutoDiscoverAutoMode,
+			defaultAutoDiscover: valid.AutoDiscoverEnabledMode,
+			projects:            []valid.Project{{}},
+			expEnabled:          false,
+		},
+		{
+			description:         "repo set auto autodiscover with a project default disabled",
+			repoAutoDiscover:    valid.AutoDiscoverAutoMode,
+			defaultAutoDiscover: valid.AutoDiscoverDisabledMode,
+			projects:            []valid.Project{{}},
+			expEnabled:          false,
+		},
+		{
+			description:         "repo unset autodiscover with no projects default enabled",
+			defaultAutoDiscover: valid.AutoDiscoverEnabledMode,
+			expEnabled:          true,
+		},
+		{
+			description:         "repo unset autodiscover with no projects default disabled",
+			defaultAutoDiscover: valid.AutoDiscoverDisabledMode,
+			expEnabled:          false,
+		},
+		{
+			description:         "repo unset autodiscover with no projects default auto",
+			defaultAutoDiscover: valid.AutoDiscoverAutoMode,
+			expEnabled:          true,
+		},
+		{
+			description:         "repo unset autodiscover with a project default enabled",
+			projects:            []valid.Project{{}},
+			defaultAutoDiscover: valid.AutoDiscoverEnabledMode,
+			expEnabled:          true,
+		},
+		{
+			description:         "repo unset autodiscover with a project default disabled",
+			projects:            []valid.Project{{}},
+			defaultAutoDiscover: valid.AutoDiscoverDisabledMode,
+			expEnabled:          false,
+		},
+		{
+			description:         "repo unset autodiscover with a project default auto",
+			projects:            []valid.Project{{}},
+			defaultAutoDiscover: valid.AutoDiscoverAutoMode,
+			expEnabled:          false,
+		},
+	}
+	for _, c := range cases {
+		t.Run(c.description, func(t *testing.T) {
+			r := valid.RepoCfg{
+				Projects:     c.projects,
+				AutoDiscover: nil,
+			}
+			if c.repoAutoDiscover != "" {
+				r.AutoDiscover = &valid.AutoDiscover{c.repoAutoDiscover}
+			}
+			enabled := r.AutoDiscoverEnabled(c.defaultAutoDiscover)
+			Equals(t, c.expEnabled, enabled)
+		})
+	}
+}