Add builtin tldr tealdeer page (#472)

Fixes #218.

docs/src/usage.txt

@@ -29,3 +29,5 @@ Options:
   -h, --help                 Print help
 
 To view the user documentation, please visit https://tealdeer-rs.github.io/tealdeer/.
+
+To view usage examples, run tldr tldr or tldr tealdeer.

pages/tealdeer.md

@@ -0,0 +1,42 @@
+# tldr
+
+> This is a builtin page that shows information for your installed tealdeer version.
+> More information: <https://tealdeer-rs.github.io/tealdeer/>.
+
+> This page shows tealdeer specific functionality. See tldr tldr for more examples.
+
+- Render a local markdown file as a tldr page:
+
+`tldr --render {{path/to/file.md}}`
+
+- Show the raw markdown source of a page instead of rendering it:
+
+`tldr --raw {{command}}`
+
+- Show file and directory paths used by tealdeer:
+
+`tldr --show-paths`
+
+- Create an initial config file:
+
+`tldr --seed-config`
+
+- Override config file location:
+
+`tldr --config-path <FILE>`
+
+- Open a custom page for a command in `$EDITOR` (creates it if it doesn't exist):
+
+`tldr --edit-page {{command}}`
+
+- Open a custom patch for a command in `$EDITOR` (appended to the existing page):
+
+`tldr --edit-patch {{command}}`
+
+- Clear the local cache:
+
+`tldr --clear-cache`
+
+- If auto update is configured, disable it for this run:
+
+`tldr --no-auto-update`

src/cache.rs

@@ -1,6 +1,6 @@
 use std::{
     fs::{self, File},
-    io::{BufReader, Cursor, ErrorKind, Read},
+    io::{Cursor, ErrorKind, Read},
     path::{Path, PathBuf},
     time::{Duration, SystemTime},
 };
@@ -277,12 +277,12 @@ impl PageLookupResult {
         self
     }
 
-    /// Create a buffered reader that sequentially reads from the page and the
+    /// Create a reader that sequentially reads from the page and the
     /// patch, as if they were concatenated.
     ///
     /// This will return an error if either the page file or the patch file
     /// cannot be opened.
-    pub fn reader(&self) -> Result<BufReader<Box<dyn Read>>> {
+    pub fn reader(&self) -> Result<Box<dyn Read>> {
         // Open page file
         let page_file = File::open(&self.page_path)
             .with_context(|| format!("Could not open page file at {}", self.page_path.display()))?;
@@ -302,11 +302,11 @@ impl PageLookupResult {
         // the page and patch files and that will read them sequentially,
         // because it avoids the boxing below. However, the performance impact
         // would first need to be shown to be significant using a benchmark.
-        Ok(BufReader::new(if let Some(patch_file) = patch_file_opt {
+        Ok(if let Some(patch_file) = patch_file_opt {
             Box::new(page_file.chain(&b"\n"[..]).chain(patch_file)) as Box<dyn Read>
         } else {
             Box::new(page_file) as Box<dyn Read>
-        }))
+        })
     }
 }
 

src/cli.rs

@@ -18,7 +18,9 @@ use crate::types::{ColorOptions, PlatformType};
 {usage-heading} {usage}
 
 {all-args}{after-help}",
-    after_help = "To view the user documentation, please visit https://tealdeer-rs.github.io/tealdeer/.",
+    after_help = "To view the user documentation, please visit https://tealdeer-rs.github.io/tealdeer/.
+
+To view usage examples, run tldr tldr or tldr tealdeer.",
     arg_required_else_help = true,
     help_expected = true,
     group = ArgGroup::new("command_or_file").args(&["command", "render"]),

src/main.rs

@@ -68,6 +68,8 @@ const APP_INFO: AppInfo = AppInfo {
     name: NAME,
     author: NAME,
 };
+static TEALDEER_PAGE: &str =
+    include_str!(concat!(env!("CARGO_MANIFEST_DIR"), "/pages/tealdeer.md"));
 
 /// Clear the cache
 fn clear_cache(cache: Cache, quietly: bool) -> Result<()> {
@@ -258,8 +260,20 @@ fn try_main(args: Cli, enable_styles: bool) -> Result<ExitCode> {
 
     // If a local file was passed in, render it and exit
     if let Some(file) = args.render {
-        let path = PageLookupResult::with_page(file);
-        print_page(&path, args.raw, enable_styles, args.pager, &config)?;
+        let reader = PageLookupResult::with_page(file).reader()?;
+        print_page(reader, args.raw, enable_styles, args.pager, &config)?;
+        return Ok(ExitCode::SUCCESS);
+    }
+
+    // The tealdeer page is embedded in the binary, no cache needed
+    if command == "tealdeer" {
+        print_page(
+            TEALDEER_PAGE.as_bytes(),
+            args.raw,
+            enable_styles,
+            args.pager,
+            &config,
+        )?;
         return Ok(ExitCode::SUCCESS);
     }
 
@@ -407,7 +421,7 @@ fn try_main(args: Cli, enable_styles: bool) -> Result<ExitCode> {
             );
         }
 
-        let Some(lookup_result) = cache.find_page(&command) else {
+        let Some(result) = cache.find_page(&command) else {
             if !args.quiet {
                 print_warning(
                     enable_styles,
@@ -419,11 +433,16 @@ fn try_main(args: Cli, enable_styles: bool) -> Result<ExitCode> {
                     ),
                 );
             }
-
             return Ok(ExitCode::FAILURE);
         };
 
-        print_page(&lookup_result, args.raw, enable_styles, args.pager, &config)?;
+        print_page(
+            result.reader()?,
+            args.raw,
+            enable_styles,
+            args.pager,
+            &config,
+        )?;
     }
 
     Ok(ExitCode::SUCCESS)

src/output.rs

@@ -1,12 +1,11 @@
 //! Functions for printing pages to the terminal
 
-use std::io::{self, BufRead, Write};
+use std::io::{self, BufRead, BufReader, Read, Write};
 
 use anyhow::{Context, Result};
 use yansi::Paint;
 
 use crate::{
-    cache::PageLookupResult,
     config::{Config, StyleConfig},
     formatter::{highlight_lines, PageSnippet},
     line_iterator::LineIterator,
@@ -30,14 +29,13 @@ fn configure_pager(enable_styles: bool) {
 
 /// Print page by path
 pub fn print_page(
-    lookup_result: &PageLookupResult,
+    reader: impl Read,
     enable_markdown: bool,
     enable_styles: bool,
     use_pager: bool,
     config: &Config,
 ) -> Result<()> {
-    // Create reader from file(s)
-    let reader = lookup_result.reader()?;
+    let reader = BufReader::new(reader);
 
     // Configure pager if applicable
     if use_pager || config.display.use_pager {

tests/lib.rs

@@ -301,6 +301,16 @@ fn test_missing_cache() {
         .stderr(contains("Page cache not found. Please run `tldr --update`"));
 }
 
+#[test]
+fn test_tealdeer_page_works_without_cache() {
+    TestEnv::new()
+        .command()
+        .args(["tealdeer"])
+        .assert()
+        .success()
+        .stdout(contains("for your installed tealdeer version"));
+}
+
 #[cfg_attr(feature = "ignore-online-tests", ignore = "online test")]
 #[test]
 fn test_update_cache_default_features() {