pdfkit not finding font files on Gatsby

node_modules/pdfkit/js/pdfkit.es.js とデータディレクトリから始め、Gatsby が .cache/functions から APIs を呼び出したときに発生する Helvetica.afm が見つからないエラーを再現します。報告された diff における標準フォントとカラープロファイルの読み込みを比較し、Gatsby のキャッシュ済み関数と通常の使用の両方で PDF 生成が機能することを確認します。

On Gatsby 5.14.1 I'm seeing an issue with pdfkit 0.16.0 unable to load font files.

Error: ENOENT: no such file or directory, open '/project-home/.cache/functions/data/Helvetica.afm'
at Object.readFileSync (node:fs:442:20)
at Object.Helvetica (webpack://project-home/./node_modules/pdfkit/js/pdfkit.es.js?:2563:54)
at new StandardFont (webpack://project-home/./node_modules/pdfkit/js/pdfkit.es.js?:2599:54)
at PDFFontFactory.open (webpack://project-home/./node_modules/pdfkit/js/pdfkit.es.js?:2899:16)
at PDFDocument.font (webpack://project-home/./node_modules/pdfkit/js/pdfkit.es.js?:2976:33)
at PDFDocument.initFonts (webpack://project-home/./node_modules/pdfkit/js/pdfkit.es.js?:2941:12)
at new PDFDocument (webpack://project-home/./node_modules/pdfkit/js/pdfkit.es.js?:5638:10)

Here is the diff that solved my problem:

diff --git a/node_modules/pdfkit/js/pdfkit.es.js b/node_modules/pdfkit/js/pdfkit.es.js
index ffc8097..3bb682b 100644
--- a/node_modules/pdfkit/js/pdfkit.es.js
+++ b/node_modules/pdfkit/js/pdfkit.es.js
@@ -2526,49 +2526,55 @@ class PDFFont {
   }
 }
 
+//**************************************************************************************
+// Lance, 25 Feb 2025 -- changed this in pdfkit.es.js to solve missing font files 
+// when Gatsby invokes APIs from .cache/functions
+// __dirname resolves to .cache/functions but font files are missing in there
+//**************************************************************************************
+const HACK_DIR = process.cwd() + '/node_modules/pdfkit/js';
+
 // This insanity is so bundlers can inline the font files
 const STANDARD_FONTS = {
   Courier() {
-    return fs.readFileSync(__dirname + '/data/Courier.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Courier.afm', 'utf8');
   },
   'Courier-Bold'() {
-    return fs.readFileSync(__dirname + '/data/Courier-Bold.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Courier-Bold.afm', 'utf8');
   },
   'Courier-Oblique'() {
-    return fs.readFileSync(__dirname + '/data/Courier-Oblique.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Courier-Oblique.afm', 'utf8');
   },
   'Courier-BoldOblique'() {
-    return fs.readFileSync(__dirname + '/data/Courier-BoldOblique.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Courier-BoldOblique.afm', 'utf8');
   },
   Helvetica() {
-    return fs.readFileSync(__dirname + '/data/Helvetica.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Helvetica.afm', 'utf8');
   },
   'Helvetica-Bold'() {
-    return fs.readFileSync(__dirname + '/data/Helvetica-Bold.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Helvetica-Bold.afm', 'utf8');
   },
   'Helvetica-Oblique'() {
-    return fs.readFileSync(__dirname + '/data/Helvetica-Oblique.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Helvetica-Oblique.afm', 'utf8');
   },
   'Helvetica-BoldOblique'() {
-    return fs.readFileSync(__dirname + '/data/Helvetica-BoldOblique.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Helvetica-BoldOblique.afm', 'utf8');
   },
   'Times-Roman'() {
-    return fs.readFileSync(__dirname + '/data/Times-Roman.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Times-Roman.afm', 'utf8');
   },
   'Times-Bold'() {
-    return fs.readFileSync(__dirname + '/data/Times-Bold.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Times-Bold.afm', 'utf8');
   },
   'Times-Italic'() {
-    return fs.readFileSync(__dirname + '/data/Times-Italic.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Times-Italic.afm', 'utf8');
   },
   'Times-BoldItalic'() {
-    return fs.readFileSync(__dirname + '/data/Times-BoldItalic.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Times-BoldItalic.afm', 'utf8');
   },
   Symbol() {
-    return fs.readFileSync(__dirname + '/data/Symbol.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/Symbol.afm', 'utf8');
   },
   ZapfDingbats() {
-    return fs.readFileSync(__dirname + '/data/ZapfDingbats.afm', 'utf8');
+    return fs.readFileSync(HACK_DIR + '/data/ZapfDingbats.afm', 'utf8');
   }
 };
 class StandardFont extends PDFFont {
@@ -5362,7 +5368,7 @@ var PDFA = {
     this._addColorOutputIntent();
   },
   _addColorOutputIntent() {
-    const iccProfile = fs.readFileSync(`${__dirname}/data/sRGB_IEC61966_2_1.icc`);
+    const iccProfile = fs.readFileSync(`${HACK_DIR}/data/sRGB_IEC61966_2_1.icc`); /* added by Lance, 25 Feb 2025 */
     const colorProfileRef = this.ref({
       Length: iccProfile.length,
       N: 3

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