From dd8a31838c8e7ac9bd175140b4058cb6f93eec54 Mon Sep 17 00:00:00 2001
From: JoostK <joost.koehoorn@gmail.com>
Date: Sat, 5 Dec 2020 14:30:45 +0100
Subject: [PATCH] refactor(compiler-cli): extract parsing of interpolation
 config (#39961)

Prior to this change the interpolation config value was cast to
`[string, string]` without checking whether there really were two
string values available. This commit extracts the logic of parsing the
interpolation config into a separate function and adds a check that
the array contains exactly two strings.

PR Close #39961
---
 .../partial_component_linker_1.ts             | 25 +++++++++++++++----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/packages/compiler-cli/linker/src/file_linker/partial_linkers/partial_component_linker_1.ts b/packages/compiler-cli/linker/src/file_linker/partial_linkers/partial_component_linker_1.ts
index 0dafc02d48..6f5c9fa4b0 100644
--- a/packages/compiler-cli/linker/src/file_linker/partial_linkers/partial_component_linker_1.ts
+++ b/packages/compiler-cli/linker/src/file_linker/partial_linkers/partial_component_linker_1.ts
@@ -38,11 +38,7 @@ export class PartialComponentLinkerVersion1<TExpression> implements PartialLinke
 export function toR3ComponentMeta<TExpression>(
     metaObj: AstObject<R3DeclareComponentMetadata, TExpression>, code: string, sourceUrl: string,
     options: LinkerOptions): R3ComponentMetadata {
-  let interpolation = DEFAULT_INTERPOLATION_CONFIG;
-  if (metaObj.has('interpolation')) {
-    interpolation = InterpolationConfig.fromArray(
-        metaObj.getArray('interpolation').map(entry => entry.getString()) as [string, string]);
-  }
+  const interpolation = parseInterpolationConfig(metaObj);
   const templateObj = metaObj.getObject('template');
   const templateSource = templateObj.getValue('source');
   const range = getTemplateRange(templateSource, code);
@@ -130,6 +126,25 @@ export function toR3ComponentMeta<TExpression>(
   };
 }
 
+/**
+ * Extract an `InterpolationConfig` from the component declaration.
+ */
+function parseInterpolationConfig<TExpression>(
+    metaObj: AstObject<R3DeclareComponentMetadata, TExpression>): InterpolationConfig {
+  if (!metaObj.has('interpolation')) {
+    return DEFAULT_INTERPOLATION_CONFIG;
+  }
+
+  const interpolationExpr = metaObj.getValue('interpolation');
+  const values = interpolationExpr.getArray().map(entry => entry.getString());
+  if (values.length !== 2) {
+    throw new FatalLinkerError(
+        interpolationExpr.expression,
+        'Unsupported interpolation config, expected an array containing exactly two strings');
+  }
+  return InterpolationConfig.fromArray(values as [string, string]);
+}
+
 /**
  * Determines the `ViewEncapsulation` mode from the AST value's symbol name.
  */