Implement the load_from_file function

The implementation is dead simple, and pretty dumb. I'm not going to
figure out all the different IO errors I might see. Instead, the
function will report that it couldn't read the file and call it good.

src/config.rs

@@ -8,6 +8,7 @@ pub enum Error {
     BadFormat,
     NoSuchProperty,
     NoSuchTable,
+    CouldntReadFile,
     TomlWrap(toml::de::Error),
 }
 
@@ -71,6 +72,17 @@ struct WholeFile {
     project_overrides: Vec<PartialConfig>,
 }
 
+fn load_from_file(path: &str) -> Result<WholeFile> {
+    let res = std::fs::read_to_string(path);
+    match res {
+        Ok(s) => read_conf_str(s.as_str()),
+        Err(e) => {
+            eprintln!("->> file io err: {:?}", e);
+            Err(Error::CouldntReadFile)
+        }
+    }
+}
+
 fn read_conf_str(text: &str) -> Result<WholeFile> {
     let mut whole = WholeFile::default();
 
@@ -98,7 +110,6 @@ fn read_conf_str(text: &str) -> Result<WholeFile> {
             .project_path(path.clone());
         whole.project_overrides.push(part_cfg);
     }
-    println!(" ->> lconf - keys {:?}", cfg_table.keys().collect::<Vec<&String>>());
     Ok(whole)
 }
 
@@ -145,6 +156,43 @@ mod tests {
 
     use super::*;
 
+    // Util for generating a reference struct
+    fn gen_expected_struct() -> WholeFile {
+        WholeFile {
+            all: PartialConfig {
+                project_path: None,
+                gitea_url: Some(String::from("http://localhost:3000")),
+                owner: None,
+                repo: None,
+                token: Some(String::from("fake-token"))
+            },
+            project_overrides: vec![
+                PartialConfig {
+                    project_path: Some(String::from("/home/robert/projects/gt-tool")),
+                    gitea_url: None,
+                    owner: Some(String::from("robert")),
+                    repo: Some(String::from("gt-tool")),
+                    token: None,
+                },
+                PartialConfig {
+                    project_path: Some(String::from("/home/robert/projects/rcalc")),
+                    gitea_url: None,
+                    owner: Some(String::from("jamis")),
+                    repo: Some(String::from("rcalc")),
+                    token: None,
+                },
+                PartialConfig {
+                    project_path: Some(String::from("/home/robert/projects/rcalc-builders")),
+                    gitea_url: None,
+                    owner: Some(String::from("jamis")),
+                    repo: Some(String::from("rcalc")),
+                    token: None,
+                },
+            
+            ],
+        }
+    }
+
     #[test]
     fn read_single_prop() -> Result<()> {
         let fx_input_str = "owner = \"dingus\"";
@@ -185,59 +233,9 @@ mod tests {
 
     #[test]
     fn read_config_string_ok() -> Result<()> {
-        let fx_sample_config_string = "
-[all]
-gitea_url = \"http://localhost:3000\"
-token = \"fake-token\"
-
-[\"/home/robert/projects/gt-tool\"]
-owner = \"robert\"
-repo = \"gt-tool\"
-
-[\"/home/robert/projects/rcalc\"]
-owner = \"jamis\"
-repo = \"rcalc\"
-
-[\"/home/robert/projects/rcalc-builders\"]
-owner = \"jamis\"
-repo = \"rcalc\"
-";
-        let fx_expected_struct = WholeFile {
-            all: PartialConfig {
-                project_path: None,
-                gitea_url: Some(String::from("http://localhost:3000")),
-                owner: None,
-                repo: None,
-                token: Some(String::from("fake-token"))
-            },
-            project_overrides: vec![
-                PartialConfig {
-                    project_path: Some(String::from("/home/robert/projects/gt-tool")),
-                    gitea_url: None,
-                    owner: Some(String::from("robert")),
-                    repo: Some(String::from("gt-tool")),
-                    token: None,
-                },
-                PartialConfig {
-                    project_path: Some(String::from("/home/robert/projects/rcalc")),
-                    gitea_url: None,
-                    owner: Some(String::from("jamis")),
-                    repo: Some(String::from("rcalc")),
-                    token: None,
-                },
-                PartialConfig {
-                    project_path: Some(String::from("/home/robert/projects/rcalc-builders")),
-                    gitea_url: None,
-                    owner: Some(String::from("jamis")),
-                    repo: Some(String::from("rcalc")),
-                    token: None,
-                },
-            
-            ],
-        };
+        let fx_sample_config_string = include_str!("../test_data/sample_config.toml");
+        let fx_expected_struct = gen_expected_struct();
         let conf = read_conf_str(fx_sample_config_string)?;
-        println!(" ->> Test conf: {:?}", conf);
-        println!(" ->> Ref  conf: {:?}", fx_expected_struct);
         
         assert_eq!(conf, fx_expected_struct);
         Ok(())
@@ -256,4 +254,30 @@ repo = \"rcalc\"
         let conf = read_conf_str(fx_sample_cfg);
         assert!(conf.is_err());
     }
+
+    #[test]
+    // File exists and has valid configuration.
+    fn load_from_file_ok() -> Result<()> {
+        let conf = load_from_file("test_data/sample_config.toml")?;
+        assert_eq!(conf, gen_expected_struct());
+        Ok(())
+    }
+
+    #[test]
+    // File does not exist.
+    fn load_from_file_missing() -> Result<()> {
+        let res = load_from_file("test_data/doesnt_exist.toml");
+        let err = res.unwrap_err();
+        assert_eq!(err, Error::CouldntReadFile);
+        Ok(())
+    }
+
+    #[test]
+    // File exists but has garbage inside.
+    // TODO: This bumps against the same semantic issue as the todo note on
+    // the 'read_config_string_empty' test
+    fn load_from_file_bad() {
+        let res = load_from_file("test_data/missing_all_table.toml");
+        assert!(res.is_err());
+    }
 }

test_data/missing_all_table.toml

@@ -0,0 +1,5 @@
+# There must be an "[all]" table or the loader will reject the config file.
+
+["/some/other/path"]
+gitea_url = "fake-url"
+

test_data/sample_config.toml

@@ -0,0 +1,15 @@
+[all]
+gitea_url = "http://localhost:3000"
+token = "fake-token"
+
+["/home/robert/projects/gt-tool"]
+owner = "robert"
+repo = "gt-tool"
+
+["/home/robert/projects/rcalc"]
+owner = "jamis"
+repo = "rcalc"
+
+["/home/robert/projects/rcalc-builders"]
+owner = "jamis"
+repo = "rcalc"