Add error codes

CHANGELOG.md

@@ -45,6 +45,16 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   [pull/484]: https://github.com/apollographql/rover/pull/484
   [issue/169]: https://github.com/apollographql/rover/issues/169
 
+- **`rover explain` command added - [JakeDawkins], [pull/457]**
+
+  When encountering most errors in Rover, there will be an error code in the format
+  `E###` printed along with the error description. Running `rover explain CODE`
+  will now print a more detailed description of the error along with any
+  resolution steps and relevant docs links.
+
+  [JakeDawkins]: https://github.com/JakeDawkins
+  [pull/457]: https://github.com/apollographql/rover/pull/457
+
 ## 🐛 Fixes
 ## 🛠 Maintenance
 

Cargo.toml

@@ -58,6 +58,10 @@ structopt = "0.3.21"
 toml = "0.5"
 tracing = "0.1.26"
 url = "2.2.0"
+termimad = "0.10.1"
+crossterm = "0.19.0"
+strum = "0.20.0"
+strum_macros = "0.20.1"
 
 [dev-dependencies]
 assert_cmd = "1.0.1"

build.rs

@@ -24,6 +24,9 @@ fn main() -> Result<()> {
     cargo_warn("updating npm package.");
     prep_npm(is_release_build)?;
 
+    cargo_warn("updating error reference docs");
+    build_error_code_reference()?;
+
     cargo_warn("exiting build.rs");
 
     Ok(())
@@ -266,3 +269,61 @@ fn process_command_output(output: &Output) -> Result<()> {
         Ok(())
     }
 }
+
+fn build_error_code_reference() -> Result<()> {
+    let docs_path = Utf8PathBuf::from("./docs/source/errors.md");
+    let codes_dir = Utf8PathBuf::from("./src/error/metadata/codes");
+    let codes = fs::read_dir(codes_dir)?;
+
+    let mut all_descriptions = String::new();
+
+    // filter out Errs and non-file entries in the `/codes` dir
+    let code_files = codes
+        .into_iter()
+        .filter_map(Result::ok)
+        .filter(|e| !e.file_type().unwrap().is_dir());
+
+    // sort the list of files alphabetically
+    let mut code_files: Vec<_> = code_files.collect();
+    code_files.sort_by_key(|f| f.path());
+
+    // for each code description, get the name of the code from the filename,
+    // and add it as a header. Then push the header and description to the
+    // all_descriptions string
+    for code in code_files {
+        let path = code.path();
+
+        let contents = fs::read_to_string(&path)?;
+        let code_name = path
+            .file_name()
+            .unwrap()
+            .to_string_lossy()
+            .replace(".md", "");
+
+        let description = format!("### {}\n\n{}\n\n", code_name, contents);
+
+        all_descriptions.push_str(&description);
+    }
+
+    let docs_content = fs::read_to_string(&docs_path)?;
+
+    // I can't get this to work with multiline matching for some reason
+    // let re = Regex::new("(?m)<!-- BUILD_CODES -->*.*").unwrap();
+    // docs_content.replace(replace_pattern, all_descriptions);
+
+    // build up a new docs page with existing content line-by-line
+    // and then concat the loaded code descriptions after
+    let mut new_content = String::new();
+    for line in docs_content.lines() {
+        new_content.push_str(line);
+        new_content.push('\n');
+        if line.contains("<!-- BUILD_CODES -->") {
+            break;
+        }
+    }
+    new_content.push_str(&all_descriptions);
+
+    fs::write(&docs_path, new_content)?;
+
+    Ok(())
+}

docs/gatsby-config.js

@@ -24,6 +24,7 @@ module.exports = {
           ],
           'Base Commands': ['graphs'],
           'Federation Commands': ['subgraphs', 'supergraphs'],
+          Reference: ['errors'],
         },
       },
     },