feat: do set key and format=text to set value for single config key

README.md

@@ -444,6 +444,83 @@ In addition to everything available via the [native HCL syntax](https://github.c
 
 `config "NAME" {}` is a layered configuration named `NAME`
 
+Let's assume `defaults.yaml` has the following content:
+
+```yaml
+api:
+  endpoint: api.example.com
+replicas: 2
+```
+
+And a Variant command that contains a job named `thing` that has a `config` block named `conf`:
+
+```hcl
+job "thing" {
+  option "env" {
+    type = string
+  }
+
+  config "myconf" {
+    source file {
+      path = "defaults.yaml"
+    }
+
+    source job {
+      name = "values"
+      args = {
+        env = opt.env
+      }
+    }
+
+    source job {
+      name = "value"
+      args = {
+        
+      }
+      key = "key1"
+      format = "text"
+    }
+  }
+
+  exec {
+    command = "echo"
+    args = list("apiendpoint=${conf.myconf.api.endpoint}, replicas=${conf.myconf.replicas}, env=${conf.myconf.env}, key1=${conf.myconf.key1}")
+  }
+}
+
+job "values" {
+  option "env" {
+    type = string
+  }
+
+  exec {
+    command = "echo"
+    args = list("env: ${opt.env}")
+  }
+}
+
+job "value" {
+  exec {
+    command = "echo"
+    args = list("val1")
+  }
+}
+```
+
+The first source loads a file at `defaults.yaml` and merges the keys and values in it into `conf`.
+
+Similarly, the second source loads keys and values from a job named `values` and merges them into `conf`.
+
+The third sets the value for the key `key1` where the value is the output of a job named `value`.
+
+The configuration `myconf` can be referenced by `${conf.myconf.KEY}` as shown in the `exec` block within the `thing` job above.
+
+Let's run `variant run thing --env prod` and the output should be:
+
+```console
+apiendpoint=api.example.com, replicas=2, env=prod, key1=val1
+```
+
 #### run
 
 `run` runs a job with args. `run` is available within `job` and `test`.

examples/config/config.variant

@@ -18,6 +18,18 @@ job "getfoo" {
   }
 }
 
+job "getbar" {
+  option "opt1" {
+    type = string
+  }
+  exec {
+    command = "echo"
+    args = [
+      "${opt.opt1}"
+    ]
+  }
+}
+
 job "config view" {
   // conf.foo
   config "foo" {
@@ -48,6 +60,17 @@ job "config view" {
       }
       format = "yaml"
     }
+
+    source job {
+      name = "getbar"
+      args = {
+        app = opt.app
+        env = opt.env
+        opt1 = "OPT1"
+      }
+      key = "bar"
+      format = "text"
+    }
   }
 
   exec {

examples/config/config_test.variant

@@ -6,7 +6,7 @@ test "app deploy" {
     exitstatus = 0
     err = ""
     out = trimspace(<<EOS
-{"app":"app1","env":"prod","getfoo":"app1,prod,PARAM1","v":"app1prod"}
+{"app":"app1","bar":"OPT1","env":"prod","getfoo":"app1,prod,PARAM1","v":"app1prod"}
 EOS
     )
   }
@@ -17,7 +17,7 @@ EOS
     exitstatus = 0
     err = ""
     out = trimspace(<<EOS
-{"app":"app2","env":"prod","getfoo":"app2,prod,PARAM1","v":"app2"}
+{"app":"app2","bar":"OPT1","env":"prod","getfoo":"app2,prod,PARAM1","v":"app2"}
 EOS
     )
   }

pkg/app/app.go

@@ -33,7 +33,13 @@ import (
 	"github.com/zclconf/go-cty/cty/gocty"
 )
 
-const NoRunMessage = "nothing to run"
+const (
+	NoRunMessage = "nothing to run"
+
+	FormatYAML = "yaml"
+
+	FormatText = "text"
+)
 
 type hcl2Loader struct {
 	Parser *hcl2parse.Parser
@@ -107,6 +113,7 @@ type Source struct {
 type SourceFile struct {
 	Path    string  `hcl:"path,attr"`
 	Default *string `hcl:"default,attr"`
+	Key     *string `hcl:"key,attr"`
 }
 
 type Step struct {
@@ -150,6 +157,7 @@ type SourceJob struct {
 	//Arguments map[string]hcl2.Expression `hcl:"args,attr"`
 	Args   hcl2.Expression `hcl:"args,attr"`
 	Format *string         `hcl:"format,attr"`
+	Key    *string         `hcl:"key,attr"`
 }
 
 type OptionSpec struct {
@@ -1293,7 +1301,7 @@ func (app *App) getConfigs(confCtx *hcl2.EvalContext, cc *HCL2Config, j JobSpec,
 
 			var format string
 
-			const FormatYAML = "yaml"
+			var key string
 
 			switch sourceSpec.Type {
 			case "file":
@@ -1314,6 +1322,10 @@ func (app *App) getConfigs(confCtx *hcl2.EvalContext, cc *HCL2Config, j JobSpec,
 				}
 
 				format = FormatYAML
+
+				if source.Key != nil {
+					key = *source.Key
+				}
 			case "job":
 				var source SourceJob
 				if err := gohcl2.DecodeBody(sourceSpec.Body, confCtx, &source); err != nil {
@@ -1349,6 +1361,10 @@ func (app *App) getConfigs(confCtx *hcl2.EvalContext, cc *HCL2Config, j JobSpec,
 				} else {
 					format = FormatYAML
 				}
+
+				if source.Key != nil {
+					key = *source.Key
+				}
 			default:
 				return cty.DynamicVal, fmt.Errorf("config source %q is not implemented. It must be either \"file\" or \"job\", so that it looks like `source file {` or `source file {`", sourceSpec.Type)
 			}
@@ -1360,6 +1376,25 @@ func (app *App) getConfigs(confCtx *hcl2.EvalContext, cc *HCL2Config, j JobSpec,
 				if err := yaml.Unmarshal(yamlData, &m); err != nil {
 					return cty.NilVal, err
 				}
+			case FormatText:
+				if key == "" {
+					return cty.NilVal, fmt.Errorf("`key` must be specified for `text`-formatted source at %d", sourceIdx)
+				}
+
+				keys := strings.Split(key, ".")
+				lastKeyIndex := len(keys) - 1
+				intermediateKeys := keys[0:lastKeyIndex]
+				lastKey := keys[lastKeyIndex]
+
+				cur := m
+
+				for _, k := range intermediateKeys {
+					if _, ok := cur[k]; !ok {
+						cur[k] = map[string]interface{}{}
+					}
+				}
+
+				cur[lastKey] = string(yamlData)
 			default:
 				return cty.NilVal, fmt.Errorf("format %q is not implemented yet. It must be \"yaml\" or omitted", format)
 			}