fix: add metadata compatibility with empty string substitutions

src/services/metadata/parse.ts

@@ -103,7 +103,9 @@ export const parseExistingMetadata = (
 };
 
 export const serializeMetadata = (objectMetadata: FileMetadata) => {
-    const dumped = unescapeLiquidSubstitutionSyntax(dump(objectMetadata).trimEnd());
+    const dumped = unescapeLiquidSubstitutionSyntax(
+        dump(objectMetadata, {forceQuotes: true}).trimEnd(),
+    );
 
     // This empty object check is a bit naive
     // The other option would be to check if all own fields are `undefined`,

tests/e2e/__snapshots__/include-toc.test.ts.snap

@@ -4,14 +4,14 @@ exports[`Include toc Nested toc inclusions with mixed including modes 1`] = `"["
 
 exports[`Include toc Nested toc inclusions with mixed including modes 2`] = `
 "---
-sourcePath: product1/core/_includes/inc.md
+sourcePath: 'product1/core/_includes/inc.md'
 ---
 This is the core include."
 `;
 
 exports[`Include toc Nested toc inclusions with mixed including modes 3`] = `
 "---
-sourcePath: product1/core/article1.md
+sourcePath: 'product1/core/article1.md'
 ---
 This is the core content of Article 1.
 
@@ -31,15 +31,15 @@ deepBase: 1
 
 exports[`Include toc Nested toc inclusions with mixed including modes 5`] = `
 "---
-sourcePath: product2/core/_includes/inc.md
+sourcePath: 'product2/core/_includes/inc.md'
 ---
 This is the core include.
 "
 `;
 
 exports[`Include toc Nested toc inclusions with mixed including modes 6`] = `
 "---
-sourcePath: product2/overlay1/product/article1.md
+sourcePath: 'product2/overlay1/product/article1.md'
 ---
 This is the overlay content of Article 1 for product 2.
 
@@ -49,15 +49,15 @@ This is the overlay content of Article 1 for product 2.
 
 exports[`Include toc Nested toc inclusions with mixed including modes 7`] = `
 "---
-sourcePath: product2/core/_includes/inc.md
+sourcePath: 'product2/core/_includes/inc.md'
 ---
 This is the core include.
 "
 `;
 
 exports[`Include toc Nested toc inclusions with mixed including modes 8`] = `
 "---
-sourcePath: product2/overlay2/product/article1.md
+sourcePath: 'product2/overlay2/product/article1.md'
 ---
 This is the overlay number #2  of Article 1 content for product 2.
 
@@ -67,15 +67,15 @@ This is the overlay number #2  of Article 1 content for product 2.
 
 exports[`Include toc Nested toc inclusions with mixed including modes 9`] = `
 "---
-sourcePath: product2/core/_includes/inc.md
+sourcePath: 'product2/core/_includes/inc.md'
 ---
 This is the core include.
 "
 `;
 
 exports[`Include toc Nested toc inclusions with mixed including modes 10`] = `
 "---
-sourcePath: product2/core/article1.md
+sourcePath: 'product2/core/article1.md'
 ---
 This is the core content of Article 1.
 
@@ -160,9 +160,9 @@ exports[`Include toc Toc is included inline, not as a new section 3`] = `
 
 exports[`Include toc Toc is included inline, not as a new section 4`] = `
 "---
-title: File A
-description: YFM description
-sourcePath: folder/fileA.md
+title: 'File A'
+description: 'YFM description'
+sourcePath: 'folder/fileA.md'
 ---
 # File A
 
@@ -176,7 +176,7 @@ Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, wh
 
 exports[`Include toc Toc is included inline, not as a new section 5`] = `
 "---
-sourcePath: folder/fileB.md
+sourcePath: 'folder/fileB.md'
 ---
 # File B
 
@@ -192,7 +192,7 @@ Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, wh
 
 exports[`Include toc Toc is included inline, not as a new section 6`] = `
 "---
-sourcePath: folder/folder/fileC.md
+sourcePath: 'folder/folder/fileC.md'
 ---
 # File C
 "
@@ -205,8 +205,8 @@ exports[`Include toc Toc is included inline, not as a new section 7`] = `
 
 exports[`Include toc Toc is included inline, not as a new section 8`] = `
 "---
-title: File A
-description: YFM description
+title: 'File A'
+description: 'YFM description'
 ---
 # File A
 
@@ -233,7 +233,7 @@ Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, wh
 
 exports[`Include toc Toc is included inline, not as a new section 10`] = `
 "---
-sourcePath: folder/folder/fileC.md
+sourcePath: 'folder/folder/fileC.md'
 ---
 # File C
 "

tests/e2e/__snapshots__/load-custom-resources.spec.ts.snap

@@ -474,12 +474,12 @@ links:
 exports[`Allow load custom resources md2md with custom resources 4`] = `
 "---
 metadata:
-  - name: yfm
-    content: builder
+  - name: 'yfm'
+    content: 'builder'
 style:
-  - _assets/style/test.css
+  - '_assets/style/test.css'
 script:
-  - _assets/script/test1.js
+  - '_assets/script/test1.js'
 ---
 
 Lorem
@@ -489,9 +489,9 @@ Lorem
 exports[`Allow load custom resources md2md with custom resources 5`] = `
 "---
 style:
-  - _assets/style/test.css
+  - '_assets/style/test.css'
 script:
-  - _assets/script/test1.js
+  - '_assets/script/test1.js'
 ---
 Lorem"
 `;

tests/e2e/__snapshots__/metadata.spec.ts.snap

@@ -207,12 +207,12 @@ links:
 exports[`Allow load custom resources md2md with metadata 3`] = `
 "---
 metadata:
-  - name: yfm
-    content: builder in page
-  - name: test-yfm
-    content: inline test
-  - name: yfm-config
-    content: config test
+  - name: 'yfm'
+    content: 'builder in page'
+  - name: 'test-yfm'
+    content: 'inline test'
+  - name: 'yfm-config'
+    content: 'config test'
 ---
 
 Lorem"
@@ -221,12 +221,12 @@ Lorem"
 exports[`Allow load custom resources md2md with metadata 4`] = `
 "---
 metadata:
-  - name: yfm
-    value: builder in config
-  - name: test-yfm
-    content: inline test
-  - name: yfm-config
-    content: config test
+  - name: 'yfm'
+    value: 'builder in config'
+  - name: 'test-yfm'
+    content: 'inline test'
+  - name: 'yfm-config'
+    content: 'config test'
 ---
 
 Lorem"

tests/integrations/services/__snapshots__/liquidInFrontMatter.test.ts.snap

@@ -11,10 +11,10 @@ exports[`Front matter (metadata) transformations do not break when a property ke
 
 exports[`Front matter (metadata) transformations do not break when a property key contains Liquid-style variable substitutions 2`] = `
 "---
-prop-{{key-name}}: This one has a substitution in a key name.
-{{key-name}}-prop: This one's key starts with a substitution.
-{{key-name}}: This one's key only consists of a substitution.
-{{ key-name }}: This one's key employs a different whitespace style in a substitution.
+prop-{{key-name}}: 'This one has a substitution in a key name.'
+{{key-name}}-prop: 'This one''s key starts with a substitution.'
+{{key-name}}: 'This one''s key only consists of a substitution.'
+{{ key-name }}: 'This one''s key employs a different whitespace style in a substitution.'
 ---
 Blah.
 "
@@ -34,15 +34,13 @@ exports[`Front matter (metadata) transformations do not break when a property va
 
 exports[`Front matter (metadata) transformations do not break when a property value contains Liquid-style variable substitutions 2`] = `
 "---
-prop1: This is a metadata property with a {{substitution}} in it.
-prop2: This one contains {{multiple}} {{substitutions}}.
-prop3: This one has {{substitutions}} of {{ different }} {{  styles}}.
-prop4: >-
-  This one has a {{substitution}} as well, but the string literal is
-  single-quoted.
-prop5: This one has no quotes at {{all}}.
-prop6: {{this}} starts with a substitution.
-prop7: {{this}} one is a multiline {{property}}.
+prop1: 'This is a metadata property with a {{substitution}} in it.'
+prop2: 'This one contains {{multiple}} {{substitutions}}.'
+prop3: 'This one has {{substitutions}} of {{ different }} {{  styles}}.'
+prop4: 'This one has a {{substitution}} as well, but the string literal is single-quoted.'
+prop5: 'This one has no quotes at {{all}}.'
+prop6: '{{this}} starts with a substitution.'
+prop7: '{{this}} one is a multiline {{property}}.'
 ---
 Blah.
 "