Replace dedent with a template-only dedent

Summary: The `dedent` module has two problems that require its replacement. First, it dedents the substitutions in addition to the template, but the substitutions need to be treated as opaque. This is because one such substitution is the whole HTML contents, which could contain important leading whitespace in a `<pre>` tag. Second, it replaces the character sequence "backslash, newline, zero-or-more-whitespace" with the empty string, and there is no way to disable this behavior, so there is consequently no way to emit a non-final line ending in a backslash. This means that it will not be possible to use `dedent` to dedent code fragments. Both of these issues are solved by implementing a template tag function that serves the intended purpose. Test Plan: Add <test>${"\n indented!"}</test>\ to the trailing backslash in `server.js`, and check the rendered output to see that both issues mentioned above are fixed.
wchargin · Jul 29, 2017 · 06475d4 · 06475d4 · exah · Aug 27, 2018
1 parent d4c20eb
commit 06475d4
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Showing 3 changed files with 40 additions and 3 deletions.
diff --git a/package.json b/package.json
@@ -18,7 +18,6 @@
     "homepage": "https://wchargin.github.io/",
     "devDependencies": {
         "copy-webpack-plugin": "^3.0.1",
-        "dedent": "^0.6.0",
         "babel-cli": "^6.11.4",
         "babel-core": "^6.13.2",
         "babel-eslint": "^6.1.2",

diff --git a/src/dedent.js b/src/dedent.js
@@ -0,0 +1,38 @@
+/*
+ * A template tag function that performs dedenting on the template, but
+ * not its arguments.
+ *
+ * For instance, given the template
+ *
+ *     |dedent`\
+ *     |    one ${one}
+ *     |        two ${two}
+ *     |    done`,
+ *
+ * where `one === "1"` and `two === "\n    2"`, the template string
+ * would expand to "one 1\n    two\n    2\ndone". Note that four spaces
+ * of indentation were stripped off of each of "one" and "two", but not
+ * from "2".
+ *
+ * Lines that contain only whitespace are not used for measuring.
+ */
+export default function dedent(strings, ...values) {
+    const lineLengths = strings.join("")
+        .split("\n")
+        .filter(line => line.trim().length !== 0)
+        .map(line => line.length - line.trimLeft().length);
+    const trimAmount = Math.min.apply(null, lineLengths);
+
+    const parts = [];
+    for (let i = 0; i < strings.length; i++) {
+        const trimmed = strings[i]
+            .split("\n")
+            .map((line, j) => i === 0 || j > 0 ? line.substr(trimAmount) : line)
+            .join("\n");
+        parts.push(trimmed);
+        if (i < values.length) {
+            parts.push(values[i]);
+        }
+    }
+    return parts.join("");
+}
diff --git a/src/server.js b/src/server.js
@@ -3,12 +3,12 @@
  * used by the static-site-generator-webpack-plugin.
  */
 
-import dedent from 'dedent';
 import {StyleSheetServer} from 'aphrodite/no-important';
 import React from 'react';
 import ReactDOMServer from 'react-dom/server';
 import {match, RouterContext} from 'react-router';
 
+import dedent from './dedent';
 import {createRoutes, resolveTitleFromPath} from './data/Routes';
 
 export default function renderStaticPage(locals, callback) {
@@ -27,7 +27,7 @@ export default function renderStaticPage(locals, callback) {
             const component = <RouterContext {...renderProps} />;
             const {html, css} = StyleSheetServer.renderStatic(() =>
                 ReactDOMServer.renderToString(component));
-            const page = dedent`
+            const page = dedent`\
                 <!DOCTYPE html>
                 <html>
                 <head>