New namespace to produce pretty annotations on input lines

.github/workflows/clojure.yml

@@ -18,13 +18,13 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Setup Java
-        uses: actions/setup-java@v4.2.1
+        uses: actions/setup-java@v4.5.0
         with:
           java-version: '11'
           distribution: 'corretto'
 
       - name: Install clojure tools
-        uses: DeLaGuardo/setup-clojure@12.5
+        uses: DeLaGuardo/setup-clojure@13.0
         with:
           cli: 1.11.2.1446
 

CHANGES.md

@@ -1,3 +1,38 @@
+## 3.3.0 -- UNRELEASED
+
+The new `clj-commons.pretty.annotations` namespace provides functions to help create pretty errors
+when parsing or interpretting text:
+
+```text
+SELECT DATE, AMT FROM PAYMENTS WHEN AMT > 10000
+             ▲▲▲               ▲▲▲▲
+             │                 │
+             │                 └╴ Unknown token
+             │
+             └╴ Invalid column name
+```
+
+Here, the errors (called "annotations") are presented as callouts targetting specific portions of the input line.
+
+The `callouts` function can handle multiple annotations on a single line, with precise control over styling and layout.
+
+The `annotate-lines` function builds on `callouts` to produce output of multiple lines from some source,
+interspersed with callouts:
+
+```text
+1: SELECT DATE, AMT
+          ▲▲▲              
+          │                              
+          └╴ Invalid column name
+2: FROM PAYMENTS WHEN AMT > 10000
+                 ▲▲▲▲                         
+                 │               
+                 └╴ Unknown token
+```                  
+
+The new `clj-commons.pretty.spec` namespace provides type and function specs for the `clj-commons.ansi` and
+`clj-commons.pretty.annotations` namespaces.
+
 ## 3.2.0 - 20 Sep 2024
 
 Added `clj-commons.ansi/pout` to replace the `pcompose` function; they are identical, but the `pout` name makes more
@@ -11,7 +46,7 @@ Added `clj-commons.format.exceptions/default-frame-rules` to supply defaults for
 which makes it much easier to override the default rules.
 
 Added function `clj-commons.format.exceptions/format-stack-trace-element` which can be used to convert a Java
-StackTraceElement into demangled, readable string, using the same logic as `format-exception.`
+StackTraceElement into a demangled, readable string, using the same logic as `format-exception.`
 
 [Closed Issues](https://github.com/clj-commons/pretty/milestone/52?closed=1)
 
@@ -44,7 +79,7 @@ Other changes:
 ## 2.6.0 - 25 Apr 2024
 
 - Font declaration in `compose` can now be a vector of individual terms, rather than a single keyword; e.g. `[:bold :red]` 
-  rather than `:bold.red`.
+  as an alternative to `:bold.red`. This can be useful when the font is computed, rather than a static literal.
 
 [Closed Issues](https://github.com/clj-commons/pretty/milestone/49?closed=1)
 

deps.edn

@@ -31,7 +31,7 @@
   {:jvm-opts ["-Dclj-commons.ansi.enabled=false"]}
 
   :nrepl
-  {:extra-deps {nrepl/nrepl {:mvn/version "1.1.1"}}
+  {:extra-deps {nrepl/nrepl {:mvn/version "1.3.0"}}
    :main-opts ["-m" "nrepl.cmdline" ]}
 
   :repl

src/clj_commons/ansi.clj

@@ -2,6 +2,8 @@
   "Help with generating textual output that includes ANSI escape codes for formatting.
   The [[compose]] function is the best starting point.
 
+  Specs for types and functions are in the [[spec]] namespace.
+
   Reference: [ANSI Escape Codes @ Wikipedia](https://en.wikipedia.org/wiki/ANSI_escape_code#SGR)."
   (:require [clojure.string :as str]
             [clj-commons.pretty-impl :refer [csi padding]]))

src/clj_commons/pretty/annotations.clj

@@ -0,0 +1,220 @@
+(ns clj-commons.pretty.annotations
+  "Tools to annotate a line of source code, in the form of callouts (lines and arrows) connected to a message.
+
+      SELECT DATE, AMT FROM PAYMENTS WHEN AMT > 10000
+                   ▲▲▲               ▲▲▲▲
+                   │                 │
+                   │                 └╴ Unknown token
+                   │
+                   └╴ Invalid column name
+
+  This kind of output is common with various kinds of parsers or interpreters.
+
+  Specs for types and functions are in the [[spec]] namespace."
+  {:added "3.3.0"})
+
+(def default-style
+  "The default style used when generating callouts.
+
+  Key       | Default | Description
+  ---       |---      |---
+  :font     | :yellow | Default font characteristics if not overrided by annotation
+  :spacing  | :tall   | One of :tall, :compact, or :minimal
+  :marker   | \"▲\"   | The marker character used to identify the offset/length of an annotation
+  :bar      | \"│\"   | Character used as the vertical bar in the callout
+  :nib      | \"└╴ \" | String used just before the annotation's message
+
+  When :spacing is :minimal, only the lines with markers or error messages appear
+  (the lines with just vertical bars are omitted).  :compact spacing is the same, but
+  one line of bars appears between the markers and the first annotation message.
+
+  Note: rendering of Unicode characters in HTML often uses incorrect fonts or adds unwanted
+  character spacing; the annotations look proper in console output."
+  {:font :yellow
+   :spacing :tall
+   :marker "▲"
+   :bar "│"
+   :nib "└╴ "})
+
+(def ^:dynamic *default-style*
+  "The default style used when no style is provided; some applications may bind or
+   override this."
+  default-style)
+
+(defn- nchars
+  [n ch]
+  (apply str (repeat n ch)))
+
+(defn- markers
+  [style annotations]
+  (let [{:keys [font marker]} style]
+    (loop [output-offset 0
+           annotations annotations
+           result [font]]
+      (if-not annotations
+        result
+        (let [{:keys [offset length font]
+               :or {length 1}} (first annotations)
+              spaces-needed (- offset output-offset)
+              result' (conj result
+                            (nchars spaces-needed \space)
+                            [font (nchars length marker)])]
+          (recur (+ offset length)
+                 (next annotations)
+                 result'))))))
+
+(defn- bars
+  [style annotations]
+  (let [{:keys [font bar]} style]
+    (loop [output-offset 0
+           annotations annotations
+           result [font]]
+      (if-not annotations
+        result
+        (let [{:keys [offset font]} (first annotations)
+              spaces-needed (- offset output-offset)
+              result' (conj result
+                            (nchars spaces-needed \space)
+                            [font bar])]
+          (recur (+ offset 1)
+                 (next annotations)
+                 result'))))))
+
+(defn- bars+message
+  [style annotations]
+  (let [{:keys [font bar nib]} style]
+    (loop [output-offset 0
+           [annotation & more-annotations] annotations
+           result [font]]
+      (let [{:keys [offset font message]} annotation
+            spaces-needed (- offset output-offset)
+            last? (not (seq more-annotations))
+            result' (conj result
+                          (nchars spaces-needed \space)
+                          [font
+                           (if last?
+                             nib
+                             bar)
+                           (when last?
+                             message)])]
+        (if last?
+          result'
+          (recur (+ offset 1)
+                 more-annotations
+                 result'))))))
+
+(defn callouts
+  "Creates callouts (the marks, bars, and messages from the example) from annotations.
+
+  Each annotation is a map:
+
+  Key       | Description
+  ---       |---
+  :message  | Composed string of the message to present
+  :offset   | Integer position (from 0) to mark on the line
+  :length   | Number of characters in the marker (min 1, defaults to 1)
+  :font     | Override of the style's font; used for marker, bars, nib, and message
+
+  The leftmost column has offset 0; some frameworks may report this as column 1
+  and an adjustment is necessary before invoking callouts.
+
+  At least one annotation is required; they will be sorted into an appropriate order.
+  Annotation's ranges should not overlap.
+
+  The messages should be relatively short, and not contain any line breaks.
+
+  Returns a sequence of composed strings, one for each line of output.
+
+  The calling code is responsible for any output; even the line being annotated;
+  this might look something like:
+
+      (ansi/perr source-line)
+      (run! ansi/perr (annotations/annotate annotations))
+
+  Uses the style defined by [[*default-style*]] if no style is provided."
+  ([annotations]
+   (callouts  *default-style* annotations))
+  ([style annotations]
+   ;; TODO: Check for overlaps
+   (let [expanded (sort-by :offset annotations)
+         {:keys [spacing]} style
+         marker-line (markers style expanded)]
+     (loop [annotations expanded
+            first? true
+            result [marker-line]]
+       (let [include-bars? (or (= spacing :tall)
+                               (and first? (= spacing :compact)))
+             result' (conj result
+                           (when include-bars?
+                             (bars style annotations))
+                           (bars+message style annotations))
+             annotations' (butlast annotations)]
+         (if (seq annotations')
+           (recur annotations' false result')
+           (remove nil? result')))))))
+
+(defn annotate-lines
+  "Intersperses numbered lines with callouts to form a new sequence
+  of composable strings where input lines are numbered, and
+  callout lines are indented beneath the input lines.
+
+  Example:
+
+  ```
+  1: SELECT DATE, AMT
+            ▲▲▲
+            │
+            └╴ Invalid column name
+  2: FROM PAYMENTS WHEN AMT > 10000
+                   ▲▲▲▲
+                   │
+                   └╴ Unknown token
+  ```
+  Each line is a map:
+
+  Key          | Value
+  ---          |---
+  :line        | Composed string for a single line of input (usually, just a string)
+  :annotations | Optional, a seq of annotation maps (used to create the callouts)
+
+  Option keys are all optional:
+
+  Key                | Value
+  ---                |---
+  :style             | style map (for callouts), defaults to [*default-style*]
+  :start-line        | Defaults to 1
+  :line-number-width | Width for the line numbers column
+
+  The :line-number-width option is usually computed from the maximum line number
+  that will be output.
+
+  Returns a seq of composed strings."
+  ([lines]
+   (annotate-lines nil lines))
+  ([opts lines]
+   (let [{:keys [style start-line]
+          :or   {style      *default-style*
+                 start-line 1}} opts
+         max-line-number (+ start-line (count lines) -1)
+         ;; inc by one to account for the ':'
+         line-number-width (inc (or (:line-number-width opts)
+                                    (-> max-line-number str count)))
+         callout-indent (repeat (nchars (inc line-number-width) " "))]
+     (loop [[line-data & more-lines] lines
+            line-number start-line
+            result []]
+       (if-not line-data
+         result
+         (let [{:keys [line annotations]} line-data
+               callout-lines (when (seq annotations)
+                               (callouts style annotations))
+               result' (cond-> (conj result
+                                     (list
+                                       [{:width line-number-width}
+                                        line-number ":"]
+                                       " "
+                                       line))
+                               callout-lines (into
+                                               (map list callout-indent callout-lines)))]
+           (recur more-lines (inc line-number) result')))))))
+