[steps] [ENG-14373] Fix multiline slack messages with env vars (#478)

* [steps] Use quotes on env var value

Added quotes around the env var value when saving it into the file.
The reason for it is that if you set the env value to something like "line 1
line 2
line 3"
without the quotes it would remove the implicit new-line characters and save it as 1 line

See: https://linear.app/expo/issue/ENG-14373/fix-multiline-slack-message-from-env-vars

* [steps] Add util function

Added an util function to replace the doubly backslashed escape character in the raw env value with actual escape characters

See: https://linear.app/expo/issue/ENG-14373/fix-multiline-slack-message-from-env-vars

* [steps] Fix escape chars

Used the previously added function to fix the escape characters when reading the raw env value from the file and updating the context

See: https://linear.app/expo/issue/ENG-14373/fix-multiline-slack-message-from-env-vars

packages/steps/bin/set-env

@@ -20,4 +20,4 @@ if [[ "$NAME" == *"="* ]]; then
   exit 1
 fi
 
-echo -n $VALUE > $__EXPO_STEPS_ENVS_DIR/$NAME
+echo -n "$VALUE" > $__EXPO_STEPS_ENVS_DIR/$NAME

packages/steps/src/BuildStep.ts

@@ -28,6 +28,7 @@ import { BuildStepEnv } from './BuildStepEnv.js';
 import { BuildRuntimePlatform } from './BuildRuntimePlatform.js';
 import { jsepEval } from './utils/jsepEval.js';
 import { interpolateJobContext } from './interpolation.js';
+import { fixEscapeCharactersInRawEnvValue } from './utils/envUtils.js';
 
 export enum BuildStepStatus {
   NEW = 'new',
@@ -484,7 +485,8 @@ export class BuildStep extends BuildStepOutputAccessor {
     const entries = await Promise.all(
       filenames.map(async (basename) => {
         const rawContents = await fs.readFile(path.join(envsDir, basename), 'utf-8');
-        return [basename, rawContents];
+        const updatedContents = fixEscapeCharactersInRawEnvValue(rawContents);
+        return [basename, updatedContents];
       })
     );
     this.ctx.global.updateEnv({

packages/steps/src/utils/envUtils.ts

@@ -0,0 +1,17 @@
+export function fixEscapeCharactersInRawEnvValue(rawValue: string): string {
+  const escapeCharsMatches = rawValue.match(/\\(\w)/g);
+  let updatedValue = rawValue;
+  for (const match of escapeCharsMatches ?? []) {
+    if (match[1] === 'n') {
+      updatedValue = updatedValue.replace(`${match[0]}${match[1]}`, '\n');
+    }
+    if (match[1] === 't') {
+      updatedValue = updatedValue.replace(`${match[0]}${match[1]}`, '\t');
+    }
+    if (match[1] === 'r') {
+      updatedValue = updatedValue.replace(`${match[0]}${match[1]}`, '\r');
+    }
+  }
+
+  return updatedValue;
+}