fix(module): only merge relevant variables overrides in config (#5138)

* fix(module): only merge relevant variables overrides in config

* chore: add a test

core/src/resolve-module.ts

@@ -7,7 +7,7 @@
  */
 
 import cloneDeep from "fast-copy"
-import { isArray, isString, keyBy } from "lodash"
+import { isArray, isString, keyBy, keys, pick, union } from "lodash"
 import { validateWithPath } from "./config/validation"
 import {
   getModuleTemplateReferences,
@@ -691,9 +691,13 @@ export class ModuleResolver {
       // Note: We're not implementing the YAML source mapping for modules
       source: undefined,
     })
-    const mergedVariables: DeepPrimitiveMap = <any>(
-      merge(moduleVariables, merge(varfileVars, this.garden.variableOverrides))
+
+    // only override the relevant variables
+    const relevantVariableOverrides = pick(
+      this.garden.variableOverrides,
+      union(keys(moduleVariables), keys(varfileVars))
     )
+    const mergedVariables: DeepPrimitiveMap = <any>merge(moduleVariables, merge(varfileVars, relevantVariableOverrides))
     return mergedVariables
   }
 }

core/test/unit/src/resolve-module.ts

@@ -38,6 +38,30 @@ describe("ModuleResolver", () => {
     expect(module.build.dependencies[0].name).to.equal("test-project-a")
   })
 
+  it("sets the relevant variables in module config from variable overrides", async () => {
+    const garden = await makeTestGardenA([], {
+      variableOverrides: {
+        foo: "override",
+        bar: "no-override",
+      },
+    })
+
+    garden.setModuleConfigs([
+      {
+        name: "test-project-a",
+        type: "test",
+        path: join(garden.projectRoot, "module-a"),
+        build: { dependencies: [], timeout: DEFAULT_BUILD_TIMEOUT_SEC },
+        variables: {
+          foo: "somevalue",
+        },
+      },
+    ])
+
+    const module = await garden.resolveModule("test-project-a")
+    expect(module.variables).to.eql({ foo: "override" })
+  })
+
   it("handles a module template reference in a build dependency name", async () => {
     const garden = await makeTestGardenA()