[Fleet] Fix incorrect conversion of string to numeric values in agent YAML (#90371)

* Convert user values back to string after yaml template compilation if they were strings originally

* Add better test cases and adjust patch

* Fix when field is undefined

* Handle array of strings too

x-pack/plugins/fleet/server/services/epm/agent/agent.test.ts

@@ -22,10 +22,23 @@ password: {{password}}
 {{#if password}}
 hidden_password: {{password}}
 {{/if}}
+{{#if optional_field}}
+optional_field: {{optional_field}}
+{{/if}}
+foo: {{bar}}
+some_text_field: {{should_be_text}}
+multi_text_field:
+{{#each multi_text}}
+  - {{this}}
+{{/each}}
       `;
     const vars = {
       paths: { value: ['/usr/local/var/log/nginx/access.log'] },
       password: { type: 'password', value: '' },
+      optional_field: { type: 'text', value: undefined },
+      bar: { type: 'text', value: 'bar' },
+      should_be_text: { type: 'text', value: '1234' },
+      multi_text: { type: 'text', value: ['1234', 'foo', 'bar'] },
     };
 
     const output = compileTemplate(vars, streamTemplate);
@@ -35,6 +48,9 @@ hidden_password: {{password}}
       exclude_files: ['.gz$'],
       processors: [{ add_locale: null }],
       password: '',
+      foo: 'bar',
+      some_text_field: '1234',
+      multi_text_field: ['1234', 'foo', 'bar'],
     });
   });
 

x-pack/plugins/fleet/server/services/epm/agent/agent.ts

@@ -58,6 +58,10 @@ function replaceVariablesInYaml(yamlVariables: { [k: string]: any }, yaml: any)
   return yaml;
 }
 
+const maybeEscapeNumericString = (value: string) => {
+  return value.length && !isNaN(+value) ? `"${value}"` : value;
+};
+
 function buildTemplateVariables(variables: PackagePolicyConfigRecord, templateStr: string) {
   const yamlValues: { [k: string]: any } = {};
   const vars = Object.entries(variables).reduce((acc, [key, recordEntry]) => {
@@ -84,6 +88,14 @@ function buildTemplateVariables(variables: PackagePolicyConfigRecord, templateSt
       const yamlKeyPlaceholder = `##${key}##`;
       varPart[lastKeyPart] = `"${yamlKeyPlaceholder}"`;
       yamlValues[yamlKeyPlaceholder] = recordEntry.value ? safeLoad(recordEntry.value) : null;
+    } else if (recordEntry.type && recordEntry.type === 'text' && recordEntry.value?.length) {
+      if (Array.isArray(recordEntry.value)) {
+        varPart[lastKeyPart] = recordEntry.value.map((value: string) =>
+          maybeEscapeNumericString(value)
+        );
+      } else {
+        varPart[lastKeyPart] = maybeEscapeNumericString(recordEntry.value);
+      }
     } else {
       varPart[lastKeyPart] = recordEntry.value;
     }