improvement(config): allow chained conditionals in template strings

For example: ${key || other-key || still-nothing || "default"}
garden-io · Jun 22, 2019 · 095e943 · 095e943
1 parent 193f2cc
commit 095e943
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Showing 5 changed files with 53 additions and 6 deletions.
diff --git a/docs/reference/template-strings.md b/docs/reference/template-strings.md
@@ -43,6 +43,19 @@ lookups of keys. However, it is possible to do nested templating. For a somewhat
 There the name of the module is pulled from the project/environment configuration, and used to find the
 appropriate key under the `modules` configuration context.
 
+You can also do conditional statements, using the `||` operator. For example:
+
+```yaml
+  # ...
+  variables:
+    log-level: ${local.env.LOG_LEVEL || "info"}
+    namespace: ${local.env.CI_BRANCH || local.username || "default"}
+```
+
+This allows you to easily set default values when certain template keys are not available, and to configure your
+project based on varying context.
+
+
 ## Reference
 
 ### Project configuration context

diff --git a/garden-service/src/docs/templates/template-strings.hbs b/garden-service/src/docs/templates/template-strings.hbs
@@ -43,6 +43,19 @@ lookups of keys. However, it is possible to do nested templating. For a somewhat
 There the name of the module is pulled from the project/environment configuration, and used to find the
 appropriate key under the `modules` configuration context.
 
+You can also do conditional statements, using the `||` operator. For example:
+
+```yaml
+  # ...
+  variables:
+    log-level: ${local.env.LOG_LEVEL || "info"}
+    namespace: ${local.env.CI_BRANCH || local.username || "default"}
+```
+
+This allows you to easily set default values when certain template keys are not available, and to configure your
+project based on varying context.
+
+
 ## Reference
 
 ### Project configuration context

diff --git a/garden-service/src/template-string-parser.pegjs b/garden-service/src/template-string-parser.pegjs
@@ -16,12 +16,24 @@ FormatString
   = FormatStart key:Key FormatEnd {
       return options.getKey(key)
   }
-  / FormatStart a:Key Or b:Key FormatEnd {
-      return options.getKey(a, { allowUndefined: true })
-        .then(result => {
-          return result || options.getKey(b, { allowUndefined: false })
+  / FormatStart head:Key tail:(Or (Key / StringLiteral))+ FormatEnd {
+      const keys = [head, ...tail.map(t => t[1])]
+
+      // Resolve all the keys
+      return Promise.all(keys.map(key =>
+        typeof key === "string" ? key : options.getKey(key, { allowUndefined: true })
+      ))
+        .then(candidates => {
+          // Return the first non-undefined value
+          for (const value of candidates) {
+            if (value !== undefined) {
+              return value
+            }
+          }
+
+          throw new options.ConfigurationError("None of the keys could be resolved in the conditional: " + text())
         })
-  }
+    }
   / FormatStart a:Key Or b:StringLiteral FormatEnd {
       return options.getKey(a, { allowUndefined: true })
         .then(result => {

diff --git a/garden-service/src/template-string.ts b/garden-service/src/template-string.ts
@@ -8,7 +8,7 @@
 
 import Bluebird = require("bluebird")
 import { asyncDeepMap } from "./util/util"
-import { GardenBaseError } from "./exceptions"
+import { GardenBaseError, ConfigurationError } from "./exceptions"
 import { ConfigContext, ContextResolveOpts, ContextResolveParams } from "./config/config-context"
 import { KeyedSet } from "./util/keyed-set"
 import { uniq } from "lodash"
@@ -48,6 +48,7 @@ export async function resolveTemplateString(string: string, context: ConfigConte
       const s = (await Bluebird.all(parts)).join("")
       return resolveTemplateString(`\$\{${s}\}`, context, { ...opts, ...resolveOpts || {} })
     },
+    ConfigurationError,
     TemplateStringError,
   })
 

diff --git a/garden-service/test/unit/src/template-string.ts b/garden-service/test/unit/src/template-string.ts
@@ -209,6 +209,14 @@ describe("resolveTemplateString", async () => {
     expect(res).to.equal("foo")
   })
 
+  it("should handle chained conditional with string fallback", async () => {
+    const res = await resolveTemplateString(
+      "${a.b || c.d || e.f || 'foo'}",
+      new TestContext({ a: {}, c: {}, e: {} }),
+    )
+    expect(res).to.equal("foo")
+  })
+
   it("should handle a conditional between two identifiers without spaces with first value set", async () => {
     const res = await resolveTemplateString(
       "${a||b}",