fix(docs-infra): always default to no linenums in `<aio-code>` (#31674)

Previously, `linenums` defaulted to true if the content was more than 10
lines long and false otherwise.

Since in most cases linenums add unnecessary visual noise, this commit
changes `linenums` to always default to false (regardless of the size of
the content). It can be still be turned on by explicitly setting to true
or a number.

PR Close #31674

aio/content/guide/docs-style-guide.md

@@ -428,7 +428,7 @@ You control the _code-example_ output by setting one or more of its attributes:
 
 * `region`- displays the source file fragment with that region name; regions are identified by _docregion_ markup in the source file, as explained [below](#region "Displaying a code fragment").
 
-* `linenums`- value may be `true`, `false`, or a `number`. When not specified, line numbers are automatically displayed when there are greater than 10 lines of code. The rarely used `number` option starts line numbering at the given value. `linenums=4` sets the starting line number to 4.
+* `linenums`- value may be `true`, `false`, or a `number`. When not specified, line numbers default to `false` (i.e. no line numbers are displayed). The rarely used `number` option starts line numbering at the given value. `linenums=4` sets the starting line number to 4.
 
 * `class`- code snippets can be styled with the CSS classes `no-box`, `code-shell`, and `avoid`.
 
@@ -465,8 +465,6 @@ A couple of observations:
 1. Omitting the `header` is fine when the source of the fragment is obvious. We just said that this is a fragment of the `app.module.ts` file which was displayed immediately above, in full, with a header.
 There's no need to repeat the header.
 
-1. The line numbers disappeared. By default, the doc viewer omits line numbers when there are fewer than 10 lines of code; it adds line numbers after that. You can turn line numbers on or off explicitly by setting the `linenums` attribute.
-
 #### Example of bad code
 
 Sometimes you want to display an example of bad code or bad design.
@@ -496,18 +494,18 @@ Code tabs display code much like _code examples_ do.  The added advantage is tha
 
 #### Code-tabs attributes
 
-* `linenums`: The value can be `true`, `false` or a number indicating the starting line number. If not specified, line numbers are enabled only when code for a tab pane has greater than 10 lines of code.
+* `linenums`: The value can be `true`, `false` or a number indicating the starting line number. If not specified, it defaults to `false`.
 
 #### Code-pane attributes
 
 * `path` - a file in the content/examples folder
 * `header` - seen in the header of a tab
-* `linenums` - overrides the `linenums` property at the `code-tabs` level for this particular pane. The value can be `true`, `false` or a number indicating the starting line number. If not specified, line numbers are enabled only when the number of lines of code are greater than 10.
+* `linenums` - overrides the `linenums` property at the `code-tabs` level for this particular pane. The value can be `true`, `false` or a number indicating the starting line number. If not specified, it defaults to `false`.
 
 The next example displays multiple code tabs, each with its own header.
 It demonstrates control over display of line numbers at both the `<code-tabs>` and `<code-pane>` levels.
 
-<code-tabs linenums="false">
+<code-tabs linenums="true">
   <code-pane
     header="app.component.html"
     path="docs-style-guide/src/app/app.component.html">
@@ -515,7 +513,7 @@ It demonstrates control over display of line numbers at both the `<code-tabs>` a
   <code-pane
     header="app.component.ts"
     path="docs-style-guide/src/app/app.component.ts"
-    linenums="true">
+    linenums="false">
   </code-pane>
   <code-pane
     header="app.component.css (heroes)"
@@ -530,11 +528,11 @@ It demonstrates control over display of line numbers at both the `<code-tabs>` a
 
 Here's the markup for that example.
 
-Note how the `linenums` attribute in the  `<code-tabs>` explicitly disables numbering for all panes.
-The `linenums` attribute in the second pane restores line numbering for _itself only_.
+Note how the `linenums` attribute in the `<code-tabs>` explicitly enables numbering for all panes.
+The `linenums` attribute in the second pane disables line numbering for _itself only_.
 
 ```html
-<code-tabs linenums="false">
+<code-tabs linenums="true">
   <code-pane
     header="app.component.html"
     path="docs-style-guide/src/app/app.component.html">
@@ -542,7 +540,7 @@ The `linenums` attribute in the second pane restores line numbering for _itself
   <code-pane
     header="app.component.ts"
     path="docs-style-guide/src/app/app.component.ts"
-    linenums="true">
+    linenums="false">
   </code-pane>
   <code-pane
     header="app.component.css (heroes)"

aio/content/marketing/test.html

@@ -3,7 +3,7 @@
 <h2>&lt;code-tabs&gt;</h2>
 
 <p>No linenums at code-tabs level</p>
-<code-tabs >
+<code-tabs>
   <code-pane header='TS code file' language='ts'>
   class {
     foo(param: string) {}
@@ -26,7 +26,7 @@
 </code-tabs>
 <p></p>
 
-<p>No linenums at code-tabs level; linenums=true for HTML pane</p>
+<p>No linenums at code-tabs level; linenums=true for second HTML pane</p>
 <code-tabs >
   <code-pane header='TS code file' language='ts'>
   class {
@@ -43,8 +43,8 @@
 <p>One line.</p>
 <code-example>const foo = 'bar'</code-example>
 
-<p>Multi-line, linenums=false.</p>
-<code-example linenums='false'>
+<p>Multi-line, linenums=true.</p>
+<code-example linenums='true'>
 &lt;hero-details <em>nghost-pmm-5&gt;
   &lt;h2 </em>ngcontent-pmm-5&gt;Bah Dah Bing&lt;/h2&gt;
   &lt;hero-team <em>ngcontent-pmm-5 </em>nghost-pmm-6&gt;
@@ -53,7 +53,7 @@
 &lt;/hero-details&gt;
 </code-example>
 
-<p>Default linenums.</p>
+<p>Default linenums (false).</p>
 <code-example>
 &lt;hero-details <em>nghost-pmm-5&gt;
   &lt;h2 </em>ngcontent-pmm-5&gt;Mister Fantastic&lt;/h2&gt;

aio/src/app/custom-elements/code/code.component.spec.ts

@@ -71,34 +71,52 @@ describe('CodeComponent', () => {
           `Formatted code (language: auto, linenums: true): ${oneLineCode}`);
     });
 
-    it('should format a small multi-line code without linenums by default', async () => {
+    it('should format a small multi-line code sample without linenums by default', () => {
       hostComponent.setCode(smallMultiLineCode);
       expect(getFormattedCode()).toBe(
           `Formatted code (language: auto, linenums: false): ${smallMultiLineCode}`);
     });
 
-    it('should add line numbers to a big multi-line code by default', async () => {
+    it('should add line numbers to a small multi-line code sample when linenums is `true`', () => {
+      hostComponent.setCode(smallMultiLineCode);
+      hostComponent.linenums = true;
+      fixture.detectChanges();
+
+      expect(getFormattedCode()).toBe(
+          `Formatted code (language: auto, linenums: true): ${smallMultiLineCode}`);
+    });
+
+    it('should add line numbers to  a small multi-line code sample when linenums is `\'true\'`', () => {
+      hostComponent.setCode(smallMultiLineCode);
+      hostComponent.linenums = 'true';
+      fixture.detectChanges();
+
+      expect(getFormattedCode()).toBe(
+          `Formatted code (language: auto, linenums: true): ${smallMultiLineCode}`);
+    });
+
+    it('should format a big multi-line code without linenums by default', () => {
       hostComponent.setCode(bigMultiLineCode);
       expect(getFormattedCode()).toBe(
-          `Formatted code (language: auto, linenums: true): ${bigMultiLineCode}`);
+          `Formatted code (language: auto, linenums: false): ${bigMultiLineCode}`);
     });
 
-    it('should format big multi-line code without linenums when linenums is `false`', async () => {
+    it('should add line numbers to a big multi-line code sample when linenums is `true`', () => {
       hostComponent.setCode(bigMultiLineCode);
-      hostComponent.linenums = false;
+      hostComponent.linenums = true;
       fixture.detectChanges();
 
       expect(getFormattedCode()).toBe(
-          `Formatted code (language: auto, linenums: false): ${bigMultiLineCode}`);
+          `Formatted code (language: auto, linenums: true): ${bigMultiLineCode}`);
     });
 
-    it('should format big multi-line code without linenums when linenums is `\'false\'`', async () => {
+    it('should add line numbers to  a big multi-line code sample when linenums is `\'true\'`', () => {
       hostComponent.setCode(bigMultiLineCode);
-      hostComponent.linenums = 'false';
+      hostComponent.linenums = 'true';
       fixture.detectChanges();
 
       expect(getFormattedCode()).toBe(
-          `Formatted code (language: auto, linenums: false): ${bigMultiLineCode}`);
+          `Formatted code (language: auto, linenums: true): ${bigMultiLineCode}`);
     });
   });
 

aio/src/app/custom-elements/code/code.component.ts

@@ -5,12 +5,6 @@ import { CopierService } from 'app/shared/copier.service';
 import { MatSnackBar } from '@angular/material/snack-bar';
 import { tap } from 'rxjs/operators';
 
-/**
- * If linenums is not set, this is the default maximum number of lines that
- * an example can display without line numbers.
- */
-const DEFAULT_LINE_NUMS_COUNT = 10;
-
 /**
  * Formatted Code Block
  *
@@ -170,9 +164,7 @@ export class CodeComponent implements OnChanges {
       typeof this.linenums === 'string' ? parseInt(this.linenums, 10) :
       this.linenums;
 
-    // if no linenums, enable line numbers if more than one line
-    return linenums == null || isNaN(linenums as number) ?
-        (code.match(/\n/g) || []).length > DEFAULT_LINE_NUMS_COUNT : linenums;
+    return (linenums != null) && !isNaN(linenums as number) && linenums;
   }
 }