support defaults. (#369)

src/Sdk/DTPipelines/Pipelines/AgentJobRequestMessage.cs

@@ -41,7 +41,8 @@ namespace GitHub.DistributedTask.Pipelines
             IEnumerable<JobStep> steps,
             IEnumerable<ContextScope> scopes,
             IList<String> fileTable,
-            TemplateToken jobOutputs)
+            TemplateToken jobOutputs,
+            IList<TemplateToken> defaults)
         {
             this.MessageType = JobRequestMessageTypes.PipelineAgentJobRequest;
             this.Plan = plan;
@@ -69,6 +70,11 @@ namespace GitHub.DistributedTask.Pipelines
                 m_environmentVariables = new List<TemplateToken>(environmentVariables);
             }
 
+            if (defaults?.Count > 0)
+            {
+                m_defaults = new List<TemplateToken>(defaults);
+            }
+
             this.ContextData = new Dictionary<String, PipelineContextData>(StringComparer.OrdinalIgnoreCase);
             if (contextData?.Count > 0)
             {
@@ -213,6 +219,21 @@ namespace GitHub.DistributedTask.Pipelines
             }
         }
 
+        /// <summary>
+        /// Gets the hierarchy of defaults to overlay, last wins.
+        /// </summary>
+        public IList<TemplateToken> Defaults
+        {
+            get
+            {
+                if (m_defaults == null)
+                {
+                    m_defaults = new List<TemplateToken>();
+                }
+                return m_defaults;
+            }
+        }
+
         /// <summary>
         /// Gets the collection of variables associated with the current context.
         /// </summary>
@@ -252,6 +273,9 @@ namespace GitHub.DistributedTask.Pipelines
             }
         }
 
+        /// <summary>
+        /// Gets the table of files used when parsing the pipeline (e.g. yaml files)
+        /// </summary>
         public IList<String> FileTable
         {
             get
@@ -372,6 +396,11 @@ namespace GitHub.DistributedTask.Pipelines
                 m_environmentVariables = null;
             }
 
+            if (m_defaults?.Count == 0)
+            {
+                m_defaults = null;
+            }
+
             if (m_fileTable?.Count == 0)
             {
                 m_fileTable = null;
@@ -406,6 +435,9 @@ namespace GitHub.DistributedTask.Pipelines
         [DataMember(Name = "EnvironmentVariables", EmitDefaultValue = false)]
         private List<TemplateToken> m_environmentVariables;
 
+        [DataMember(Name = "Defaults", EmitDefaultValue = false)]
+        private List<TemplateToken> m_defaults;
+
         [DataMember(Name = "FileTable", EmitDefaultValue = false)]
         private List<String> m_fileTable;
 

src/Sdk/DTPipelines/Pipelines/ObjectTemplating/PipelineTemplateConstants.cs

@@ -14,6 +14,7 @@ namespace GitHub.DistributedTask.Pipelines.ObjectTemplating
         public const String Clean = "clean";
         public const String Container = "container";
         public const String ContinueOnError = "continue-on-error";
+        public const String Defaults = "defaults";
         public const String Env = "env";
         public const String Event = "event";
         public const String EventPattern = "github.event";
@@ -29,6 +30,7 @@ namespace GitHub.DistributedTask.Pipelines.ObjectTemplating
         public const String Include = "include";
         public const String Inputs = "inputs";
         public const String Job = "job";
+        public const String JobDefaultsRun = "job-defaults-run";
         public const String JobOutputs = "job-outputs";
         public const String Jobs = "jobs";
         public const String Labels = "labels";

src/Sdk/DTPipelines/Pipelines/ObjectTemplating/PipelineTemplateEvaluator.cs

@@ -267,6 +267,42 @@ namespace GitHub.DistributedTask.Pipelines.ObjectTemplating
             return result;
         }
 
+        public Dictionary<String, String> EvaluateJobDefaultsRun(
+            TemplateToken token,
+            DictionaryContextData contextData)
+        {
+            var result = default(Dictionary<String, String>);
+
+            if (token != null && token.Type != TokenType.Null)
+            {
+                var context = CreateContext(contextData);
+                try
+                {
+                    token = TemplateEvaluator.Evaluate(context, PipelineTemplateConstants.JobDefaultsRun, token, 0, null, omitHeader: true);
+                    context.Errors.Check();
+                    result = new Dictionary<String, String>(StringComparer.OrdinalIgnoreCase);
+                    var mapping = token.AssertMapping("defaults run");
+                    foreach (var pair in mapping)
+                    {
+                        // Literal key
+                        var key = pair.Key.AssertString("defaults run key");
+
+                        // Literal value
+                        var value = pair.Value.AssertString("defaults run value");
+                        result[key.Value] = value.Value;
+                    }
+                }
+                catch (Exception ex) when (!(ex is TemplateValidationException))
+                {
+                    context.Errors.Add(ex);
+                }
+
+                context.Errors.Check();
+            }
+
+            return result;
+        }
+
         public IList<KeyValuePair<String, JobContainer>> EvaluateJobServiceContainers(
             TemplateToken token,
             DictionaryContextData contextData)

src/Sdk/DTPipelines/workflow-v1.0.json

@@ -9,6 +9,7 @@
         "properties": {
           "on": "any",
           "name": "string",
+          "defaults": "workflow-defaults",
           "env": "workflow-env",
           "jobs": "jobs"
         }
@@ -125,6 +126,23 @@
       "string": {}
     },
 
+    "workflow-defaults": {
+      "mapping": {
+        "properties": {
+          "run": "workflow-defaults-run"
+        }
+      }
+    },
+
+    "workflow-defaults-run": {
+      "mapping": {
+        "properties": {
+          "shell": "non-empty-string",
+          "working-directory": "non-empty-string"
+        }
+      }
+    },
+
     "workflow-env": {
       "context": [
         "github",
@@ -161,6 +179,7 @@
           "services": "services",
           "env": "job-env",
           "outputs": "job-outputs",
+          "defaults": "job-defaults",
           "steps": "steps"
         }
       }
@@ -289,6 +308,30 @@
       }
     },
 
+    "job-defaults": {
+      "mapping": {
+        "properties": {
+          "run": "job-defaults-run"
+        }
+      }
+    },
+
+    "job-defaults-run": {
+      "context": [
+        "github",
+        "strategy",
+        "matrix",
+        "needs",
+        "env"
+      ],
+      "mapping": {
+        "properties": {
+          "shell": "non-empty-string",
+          "working-directory": "non-empty-string"
+        }
+      }
+    },
+
     "job-outputs": {
       "mapping": {
         "loose-key-type": "non-empty-string",